15 files changed, 1555 insertions, 2 deletions
diff --git a/Documentation/devicetree/bindings/gpio/apple,smc-gpio.yaml b/Documentation/devicetree/bindings/gpio/apple,smc-gpio.yaml
new file mode 100644
index 00000000000000..42b1bc0a10c97a
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/apple,smc-gpio.yaml
@@ -0,0 +1,29 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/gpio/apple,smc-gpio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple Mac System Management Controller GPIO
+
+maintainers:
+  - Sven Peter <sven@kernel.org>
+
+description:
+  Apple Mac System Management Controller GPIO block.
+
+properties:
+  compatible:
+    const: apple,smc-gpio
+
+  gpio-controller: true
+
+  '#gpio-cells':
+    const: 2
+
+required:
+  - compatible
+  - gpio-controller
+  - '#gpio-cells'
+
+additionalProperties: false
diff --git a/Documentation/devicetree/bindings/mfd/apple,smc.yaml b/Documentation/devicetree/bindings/mfd/apple,smc.yaml
new file mode 100644
index 00000000000000..8a10e270d421ec
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/apple,smc.yaml
@@ -0,0 +1,79 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mfd/apple,smc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple Mac System Management Controller
+
+maintainers:
+  - Sven Peter <sven@kernel.org>
+
+description:
+  Apple Mac System Management Controller implements various functions
+  such as GPIO, RTC, power, reboot.
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - apple,t6000-smc
+          - apple,t8103-smc
+          - apple,t8112-smc
+      - const: apple,smc
+
+  reg:
+    items:
+      - description: SMC area
+      - description: SRAM area
+
+  reg-names:
+    items:
+      - const: smc
+      - const: sram
+
+  mboxes:
+    maxItems: 1
+
+  gpio:
+    $ref: /schemas/gpio/apple,smc-gpio.yaml
+
+  reboot:
+    $ref: /schemas/power/reset/apple,smc-reboot.yaml
+
+additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - mboxes
+
+examples:
+  - |
+    soc {
+      #address-cells = <2>;
+      #size-cells = <2>;
+
+      smc@23e400000 {
+        compatible = "apple,t8103-smc", "apple,smc";
+        reg = <0x2 0x3e400000 0x0 0x4000>,
+               <0x2 0x3fe00000 0x0 0x100000>;
+        reg-names = "smc", "sram";
+        mboxes = <&smc_mbox>;
+
+        smc_gpio: gpio {
+          compatible = "apple,smc-gpio";
+          gpio-controller;
+          #gpio-cells = <2>;
+        };
+
+        reboot {
+          compatible = "apple,smc-reboot";
+          nvmem-cells = <&shutdown_flag>, <&boot_stage>,
+                        <&boot_error_count>, <&panic_count>;
+          nvmem-cell-names = "shutdown_flag", "boot_stage",
+                             "boot_error_count", "panic_count";
+        };
+      };
+    };
diff --git a/Documentation/devicetree/bindings/power/reset/apple,smc-reboot.yaml b/Documentation/devicetree/bindings/power/reset/apple,smc-reboot.yaml
new file mode 100644
index 00000000000000..ce5ed88493cdb6
--- /dev/null
+++ b/Documentation/devicetree/bindings/power/reset/apple,smc-reboot.yaml
@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/power/reset/apple,smc-reboot.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple SMC Reboot Controller
+
+description:
+  The Apple System Management Controller (SMC) provides reboot functionality
+  on Apple Silicon SoCs. It uses NVMEM cells to store and track various
+  system state information related to boot, shutdown, and panic events.
+
+maintainers:
+  - Sven Peter <sven@kernel.org>
+
+properties:
+  compatible:
+    const: apple,smc-reboot
+
+  nvmem-cells:
+    items:
+      - description: Flag indicating shutdown (as opposed to reboot)
+      - description: Stage at which the boot process stopped (0x30 for normal boot)
+      - description: Counter for boot errors
+      - description: Counter for system panics
+
+  nvmem-cell-names:
+    items:
+      - const: shutdown_flag
+      - const: boot_stage
+      - const: boot_error_count
+      - const: panic_count
+
+required:
+  - compatible
+  - nvmem-cells
+  - nvmem-cell-names
+
+additionalProperties: false
diff --git a/MAINTAINERS b/MAINTAINERS
index 971ee194ee83fb..698bafdc99684a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2332,6 +2332,7 @@ F:	Documentation/devicetree/bindings/arm/apple/*
 F:	Documentation/devicetree/bindings/clock/apple,nco.yaml
 F:	Documentation/devicetree/bindings/cpufreq/apple,cluster-cpufreq.yaml
 F:	Documentation/devicetree/bindings/dma/apple,admac.yaml
+F:	Documentation/devicetree/bindings/gpio/apple,smc-gpio.yaml
 F:	Documentation/devicetree/bindings/i2c/apple,i2c.yaml
 F:	Documentation/devicetree/bindings/input/touchscreen/apple,z2-multitouch.yaml
 F:	Documentation/devicetree/bindings/interrupt-controller/apple,*
@@ -2339,6 +2340,7 @@ F:	Documentation/devicetree/bindings/iommu/apple,dart.yaml
 F:	Documentation/devicetree/bindings/iommu/apple,sart.yaml
 F:	Documentation/devicetree/bindings/leds/backlight/apple,dwi-bl.yaml
 F:	Documentation/devicetree/bindings/mailbox/apple,mailbox.yaml
+F:	Documentation/devicetree/bindings/mfd/apple,smc.yaml
 F:	Documentation/devicetree/bindings/net/bluetooth/brcm,bcm4377-bluetooth.yaml
 F:	Documentation/devicetree/bindings/nvme/apple,nvme-ans.yaml
 F:	Documentation/devicetree/bindings/nvmem/apple,efuses.yaml
@@ -2346,6 +2348,7 @@ F:	Documentation/devicetree/bindings/nvmem/apple,spmi-nvmem.yaml
 F:	Documentation/devicetree/bindings/pci/apple,pcie.yaml
 F:	Documentation/devicetree/bindings/pinctrl/apple,pinctrl.yaml
 F:	Documentation/devicetree/bindings/power/apple*
+F:	Documentation/devicetree/bindings/power/reset/apple,smc-reboot.yaml
 F:	Documentation/devicetree/bindings/pwm/apple,s5l-fpwm.yaml
 F:	Documentation/devicetree/bindings/spi/apple,spi.yaml
 F:	Documentation/devicetree/bindings/spmi/apple,spmi.yaml
@@ -2355,6 +2358,7 @@ F:	drivers/bluetooth/hci_bcm4377.c
 F:	drivers/clk/clk-apple-nco.c
 F:	drivers/cpufreq/apple-soc-cpufreq.c
 F:	drivers/dma/apple-admac.c
+F:	drivers/gpio/gpio-macsmc.c
 F:	drivers/pmdomain/apple/
 F:	drivers/i2c/busses/i2c-pasemi-core.c
 F:	drivers/i2c/busses/i2c-pasemi-platform.c
@@ -2362,10 +2366,12 @@ F:	drivers/input/touchscreen/apple_z2.c
 F:	drivers/iommu/apple-dart.c
 F:	drivers/iommu/io-pgtable-dart.c
 F:	drivers/irqchip/irq-apple-aic.c
+F:	drivers/mfd/macsmc.c
 F:	drivers/nvme/host/apple.c
 F:	drivers/nvmem/apple-efuses.c
 F:	drivers/nvmem/apple-spmi-nvmem.c
 F:	drivers/pinctrl/pinctrl-apple-gpio.c
+F:	drivers/power/reset/macsmc-reboot.c
 F:	drivers/pwm/pwm-apple.c
 F:	drivers/soc/apple/*
 F:	drivers/spi/spi-apple.c
@@ -2374,6 +2380,7 @@ F:	drivers/video/backlight/apple_dwi_bl.c
 F:	drivers/watchdog/apple_wdt.c
 F:	include/dt-bindings/interrupt-controller/apple-aic.h
 F:	include/dt-bindings/pinctrl/apple.h
+F:	include/linux/mfd/macsmc.h
 F:	include/linux/soc/apple/*
 F:	include/uapi/drm/asahi_drm.h
 
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 12bdf6e965f19c..6e3c3f0e3dcfeb 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1473,6 +1473,16 @@ config GPIO_LP87565
 	  This driver can also be built as a module. If so, the module will be
 	  called gpio-lp87565.
 
+config GPIO_MACSMC
+	tristate "Apple Mac SMC GPIO"
+	depends on MFD_MACSMC
+	help
+	  Support for GPIOs controlled by the SMC microcontroller on Apple Mac
+	  systems.
+
+	  This driver can also be built as a module. If so, the module will be
+	  called gpio-macsmc.
+
 config GPIO_MADERA
 	tristate "Cirrus Logic Madera class codecs"
 	depends on PINCTRL_MADERA
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 88dedd298256c1..3e5bc90ba59e56 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -99,6 +99,7 @@ obj-$(CONFIG_GPIO_LP873X)		+= gpio-lp873x.o
 obj-$(CONFIG_GPIO_LP87565)		+= gpio-lp87565.o
 obj-$(CONFIG_GPIO_LPC18XX)		+= gpio-lpc18xx.o
 obj-$(CONFIG_GPIO_LPC32XX)		+= gpio-lpc32xx.o
+obj-$(CONFIG_GPIO_MACSMC)		+= gpio-macsmc.o
 obj-$(CONFIG_GPIO_MADERA)		+= gpio-madera.o
 obj-$(CONFIG_GPIO_MAX3191X)		+= gpio-max3191x.o
 obj-$(CONFIG_GPIO_MAX7300)		+= gpio-max7300.o
diff --git a/drivers/gpio/gpio-macsmc.c b/drivers/gpio/gpio-macsmc.c
new file mode 100644
index 00000000000000..7570d9e89adfff
--- /dev/null
+++ b/drivers/gpio/gpio-macsmc.c
@@ -0,0 +1,292 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SMC GPIO driver
+ * Copyright The Asahi Linux Contributors
+ *
+ * This driver implements basic SMC PMU GPIO support that can read inputs
+ * and write outputs. Mode changes and IRQ config are not yet implemented.
+ */
+
+#include <linux/bitmap.h>
+#include <linux/device.h>
+#include <linux/gpio/driver.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/macsmc.h>
+
+#define MAX_GPIO 64
+
+/*
+ * Commands 0-6 are, presumably, the intended API.
+ * Command 0xff lets you get/set the pin configuration in detail directly,
+ * but the bit meanings seem not to be stable between devices/PMU hardware
+ * versions.
+ *
+ * We're going to try to make do with the low commands for now.
+ * We don't implement pin mode changes at this time.
+ */
+
+#define CMD_ACTION	(0 << 24)
+#define CMD_OUTPUT	(1 << 24)
+#define CMD_INPUT	(2 << 24)
+#define CMD_PINMODE	(3 << 24)
+#define CMD_IRQ_ENABLE	(4 << 24)
+#define CMD_IRQ_ACK	(5 << 24)
+#define CMD_IRQ_MODE	(6 << 24)
+#define CMD_CONFIG	(0xff << 24)
+
+#define MODE_INPUT	0
+#define MODE_OUTPUT	1
+#define MODE_VALUE_0	0
+#define MODE_VALUE_1	2
+
+#define IRQ_MODE_HIGH		0
+#define IRQ_MODE_LOW		1
+#define IRQ_MODE_RISING		2
+#define IRQ_MODE_FALLING	3
+#define IRQ_MODE_BOTH		4
+
+#define CONFIG_MASK	GENMASK(23, 16)
+#define CONFIG_VAL	GENMASK(7, 0)
+
+#define CONFIG_OUTMODE	GENMASK(7, 6)
+#define CONFIG_IRQMODE	GENMASK(5, 3)
+#define CONFIG_PULLDOWN	BIT(2)
+#define CONFIG_PULLUP	BIT(1)
+#define CONFIG_OUTVAL	BIT(0)
+
+/*
+ * Output modes seem to differ depending on the PMU in use... ?
+ * j274 / M1 (Sera PMU):
+ *   0 = input
+ *   1 = output
+ *   2 = open drain
+ *   3 = disable
+ * j314 / M1Pro (Maverick PMU):
+ *   0 = input
+ *   1 = open drain
+ *   2 = output
+ *   3 = ?
+ */
+
+struct macsmc_gpio {
+	struct device *dev;
+	struct apple_smc *smc;
+	struct gpio_chip gc;
+
+	int first_index;
+};
+
+static int macsmc_gpio_nr(smc_key key)
+{
+	int low = hex_to_bin(key & 0xff);
+	int high = hex_to_bin((key >> 8) & 0xff);
+
+	if (low < 0 || high < 0)
+		return -1;
+
+	return low | (high << 4);
+}
+
+static int macsmc_gpio_key(unsigned int offset)
+{
+	return _SMC_KEY("gP\0\0") | hex_asc_hi(offset) << 8 | hex_asc_lo(offset);
+}
+
+static int macsmc_gpio_find_first_gpio_index(struct macsmc_gpio *smcgp)
+{
+	struct apple_smc *smc = smcgp->smc;
+	smc_key key = macsmc_gpio_key(0);
+	smc_key first_key, last_key;
+	int start, count, ret;
+
+	/* Return early if the key is out of bounds */
+	ret = apple_smc_get_key_by_index(smc, 0, &first_key);
+	if (ret)
+		return ret;
+	if (key <= first_key)
+		return -ENODEV;
+
+	ret = apple_smc_get_key_by_index(smc, smc->key_count - 1, &last_key);
+	if (ret)
+		return ret;
+	if (key > last_key)
+		return -ENODEV;
+
+	/* Binary search to find index of first SMC key bigger or equal to key */
+	start = 0;
+	count = smc->key_count;
+	while (count > 1) {
+		smc_key pkey;
+		int pivot = start + ((count - 1) >> 1);
+
+		ret = apple_smc_get_key_by_index(smc, pivot, &pkey);
+		if (ret < 0)
+			return ret;
+
+		if (pkey == key)
+			return pivot;
+
+		pivot++;
+
+		if (pkey < key) {
+			count -= pivot - start;
+			start = pivot;
+		} else {
+			count = pivot - start;
+		}
+	}
+
+	return start;
+}
+
+static int macsmc_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+	struct macsmc_gpio *smcgp = gpiochip_get_data(gc);
+	smc_key key = macsmc_gpio_key(offset);
+	u32 val;
+	int ret;
+
+	/* First try reading the explicit pin mode register */
+	ret = apple_smc_rw_u32(smcgp->smc, key, CMD_PINMODE, &val);
+	if (!ret)
+		return (val & MODE_OUTPUT) ? GPIO_LINE_DIRECTION_OUT : GPIO_LINE_DIRECTION_IN;
+
+	/*
+	 * Less common IRQ configs cause CMD_PINMODE to fail, and so does open drain mode.
+	 * Fall back to reading IRQ mode, which will only succeed for inputs.
+	 */
+	ret = apple_smc_rw_u32(smcgp->smc, key, CMD_IRQ_MODE, &val);
+	return ret ? GPIO_LINE_DIRECTION_OUT : GPIO_LINE_DIRECTION_IN;
+}
+
+static int macsmc_gpio_get(struct gpio_chip *gc, unsigned int offset)
+{
+	struct macsmc_gpio *smcgp = gpiochip_get_data(gc);
+	smc_key key = macsmc_gpio_key(offset);
+	u32 cmd, val;
+	int ret;
+
+	ret = macsmc_gpio_get_direction(gc, offset);
+	if (ret < 0)
+		return ret;
+
+	if (ret == GPIO_LINE_DIRECTION_OUT)
+		cmd = CMD_OUTPUT;
+	else
+		cmd = CMD_INPUT;
+
+	ret = apple_smc_rw_u32(smcgp->smc, key, cmd, &val);
+	if (ret < 0)
+		return ret;
+
+	return val ? 1 : 0;
+}
+
+static int macsmc_gpio_set(struct gpio_chip *gc, unsigned int offset, int value)
+{
+	struct macsmc_gpio *smcgp = gpiochip_get_data(gc);
+	smc_key key = macsmc_gpio_key(offset);
+	int ret;
+
+	value |= CMD_OUTPUT;
+	ret = apple_smc_write_u32(smcgp->smc, key, CMD_OUTPUT | value);
+	if (ret < 0)
+		dev_err(smcgp->dev, "GPIO set failed %p4ch = 0x%x\n",
+			&key, value);
+
+	return ret;
+}
+
+static int macsmc_gpio_init_valid_mask(struct gpio_chip *gc,
+				       unsigned long *valid_mask, unsigned int ngpios)
+{
+	struct macsmc_gpio *smcgp = gpiochip_get_data(gc);
+	int count;
+	int i;
+
+	count = min(smcgp->smc->key_count, MAX_GPIO);
+
+	bitmap_zero(valid_mask, ngpios);
+
+	for (i = 0; i < count; i++) {
+		int ret, gpio_nr;
+		smc_key key;
+
+		ret = apple_smc_get_key_by_index(smcgp->smc, smcgp->first_index + i, &key);
+		if (ret < 0)
+			return ret;
+
+		if (key > SMC_KEY(gPff))
+			break;
+
+		gpio_nr = macsmc_gpio_nr(key);
+		if (gpio_nr < 0 || gpio_nr > MAX_GPIO) {
+			dev_err(smcgp->dev, "Bad GPIO key %p4ch\n", &key);
+			continue;
+		}
+
+		set_bit(gpio_nr, valid_mask);
+	}
+
+	return 0;
+}
+
+static int macsmc_gpio_probe(struct platform_device *pdev)
+{
+	struct macsmc_gpio *smcgp;
+	struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
+	smc_key key;
+	int ret;
+
+	smcgp = devm_kzalloc(&pdev->dev, sizeof(*smcgp), GFP_KERNEL);
+	if (!smcgp)
+		return -ENOMEM;
+
+	smcgp->dev = &pdev->dev;
+	smcgp->smc = smc;
+
+	smcgp->first_index = macsmc_gpio_find_first_gpio_index(smcgp);
+	if (smcgp->first_index < 0)
+		return smcgp->first_index;
+
+	ret = apple_smc_get_key_by_index(smc, smcgp->first_index, &key);
+	if (ret < 0)
+		return ret;
+
+	if (key > macsmc_gpio_key(MAX_GPIO - 1))
+		return -ENODEV;
+
+	dev_info(smcgp->dev, "First GPIO key: %p4ch\n", &key);
+
+	smcgp->gc.label = "macsmc-pmu-gpio";
+	smcgp->gc.owner = THIS_MODULE;
+	smcgp->gc.get = macsmc_gpio_get;
+	smcgp->gc.set_rv = macsmc_gpio_set;
+	smcgp->gc.get_direction = macsmc_gpio_get_direction;
+	smcgp->gc.init_valid_mask = macsmc_gpio_init_valid_mask;
+	smcgp->gc.can_sleep = true;
+	smcgp->gc.ngpio = MAX_GPIO;
+	smcgp->gc.base = -1;
+	smcgp->gc.parent = &pdev->dev;
+
+	return devm_gpiochip_add_data(&pdev->dev, &smcgp->gc, smcgp);
+}
+
+static const struct of_device_id macsmc_gpio_of_table[] = {
+	{ .compatible = "apple,smc-gpio", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, macsmc_gpio_of_table);
+
+static struct platform_driver macsmc_gpio_driver = {
+	.driver = {
+		.name = "macsmc-gpio",
+		.of_match_table = macsmc_gpio_of_table,
+	},
+	.probe = macsmc_gpio_probe,
+};
+module_platform_driver(macsmc_gpio_driver);
+
+MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_DESCRIPTION("Apple SMC GPIO driver");
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 6fb3768e3d71cb..c6cc423608877b 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -285,6 +285,24 @@ config MFD_CS42L43_SDW
 	  Select this to support the Cirrus Logic CS42L43 PC CODEC with
 	  headphone and class D speaker drivers over SoundWire.
 
+config MFD_MACSMC
+	tristate "Apple Silicon System Management Controller (SMC)"
+	depends on ARCH_APPLE || COMPILE_TEST
+	depends on OF
+	depends on APPLE_RTKIT
+	select MFD_CORE
+	help
+	  The System Management Controller (SMC) on Apple Silicon machines is a
+	  piece of hardware that exposes various functionalities such as
+	  temperature sensors, voltage/power meters, shutdown/reboot handling,
+	  GPIOs and more.
+
+	  Communication happens via a shared mailbox using the RTKit protocol
+	  which is also used for other co-processors. The SMC protocol then
+	  allows reading and writing many different keys which implement the
+	  various features. The MFD core device handles this protocol and
+	  exposes it to the sub-devices.
+
 config MFD_MADERA
 	tristate "Cirrus Logic Madera codecs"
 	select MFD_CORE
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 79495f9f3457b8..f7bdedd5a66d16 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -21,6 +21,7 @@ obj-$(CONFIG_MFD_CS42L43_SDW)	+= cs42l43-sdw.o
 obj-$(CONFIG_MFD_ENE_KB3930)	+= ene-kb3930.o
 obj-$(CONFIG_MFD_EXYNOS_LPASS)	+= exynos-lpass.o
 obj-$(CONFIG_MFD_GATEWORKS_GSC)	+= gateworks-gsc.o
+obj-$(CONFIG_MFD_MACSMC)	+= macsmc.o
 
 obj-$(CONFIG_MFD_TI_LP873X)	+= lp873x.o
 obj-$(CONFIG_MFD_TI_LP87565)	+= lp87565.o
diff --git a/drivers/mfd/macsmc.c b/drivers/mfd/macsmc.c
new file mode 100644
index 00000000000000..870c8b2028a8fc
--- /dev/null
+++ b/drivers/mfd/macsmc.c
@@ -0,0 +1,498 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SMC (System Management Controller) MFD driver
+ *
+ * Copyright The Asahi Linux Contributors
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/math.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/macsmc.h>
+#include <linux/notifier.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/overflow.h>
+#include <linux/platform_device.h>
+#include <linux/soc/apple/rtkit.h>
+#include <linux/unaligned.h>
+
+#define SMC_ENDPOINT			0x20
+
+/* We don't actually know the true size here but this seem reasonable */
+#define SMC_SHMEM_SIZE			0x1000
+#define SMC_MAX_SIZE			255
+
+#define SMC_MSG_READ_KEY		0x10
+#define SMC_MSG_WRITE_KEY		0x11
+#define SMC_MSG_GET_KEY_BY_INDEX	0x12
+#define SMC_MSG_GET_KEY_INFO		0x13
+#define SMC_MSG_INITIALIZE		0x17
+#define SMC_MSG_NOTIFICATION		0x18
+#define SMC_MSG_RW_KEY			0x20
+
+#define SMC_DATA			GENMASK_ULL(63, 32)
+#define SMC_WSIZE			GENMASK_ULL(31, 24)
+#define SMC_SIZE			GENMASK_ULL(23, 16)
+#define SMC_ID				GENMASK_ULL(15, 12)
+#define SMC_MSG				GENMASK_ULL(7, 0)
+#define SMC_RESULT			SMC_MSG
+
+#define SMC_TIMEOUT_MS		500
+
+static const struct mfd_cell apple_smc_devs[] = {
+	MFD_CELL_OF("macsmc-gpio", NULL, NULL, 0, 0, "apple,smc-gpio"),
+	MFD_CELL_OF("macsmc-reboot", NULL, NULL, 0, 0, "apple,smc-reboot"),
+};
+
+static int apple_smc_cmd_locked(struct apple_smc *smc, u64 cmd, u64 arg,
+				  u64 size, u64 wsize, u32 *ret_data)
+{
+	u8 result;
+	int ret;
+	u64 msg;
+
+	lockdep_assert_held(&smc->mutex);
+
+	if (smc->boot_stage != APPLE_SMC_INITIALIZED)
+		return -EIO;
+	if (smc->atomic_mode)
+		return -EIO;
+
+	reinit_completion(&smc->cmd_done);
+
+	smc->msg_id = (smc->msg_id + 1) & 0xf;
+	msg = (FIELD_PREP(SMC_MSG, cmd) |
+	       FIELD_PREP(SMC_SIZE, size) |
+	       FIELD_PREP(SMC_WSIZE, wsize) |
+	       FIELD_PREP(SMC_ID, smc->msg_id) |
+	       FIELD_PREP(SMC_DATA, arg));
+
+	ret = apple_rtkit_send_message(smc->rtk, SMC_ENDPOINT, msg, NULL, false);
+	if (ret) {
+		dev_err(smc->dev, "Failed to send command\n");
+		return ret;
+	}
+
+	if (wait_for_completion_timeout(&smc->cmd_done, msecs_to_jiffies(SMC_TIMEOUT_MS)) <= 0) {
+		dev_err(smc->dev, "Command timed out (%llx)", msg);
+		return -ETIMEDOUT;
+	}
+
+	if (FIELD_GET(SMC_ID, smc->cmd_ret) != smc->msg_id) {
+		dev_err(smc->dev, "Command sequence mismatch (expected %d, got %d)\n",
+			smc->msg_id, (unsigned int)FIELD_GET(SMC_ID, smc->cmd_ret));
+		return -EIO;
+	}
+
+	result = FIELD_GET(SMC_RESULT, smc->cmd_ret);
+	if (result)
+		return -EIO;
+
+	if (ret_data)
+		*ret_data = FIELD_GET(SMC_DATA, smc->cmd_ret);
+
+	return FIELD_GET(SMC_SIZE, smc->cmd_ret);
+}
+
+static int apple_smc_cmd(struct apple_smc *smc, u64 cmd, u64 arg,
+			 u64 size, u64 wsize, u32 *ret_data)
+{
+	guard(mutex)(&smc->mutex);
+
+	return apple_smc_cmd_locked(smc, cmd, arg, size, wsize, ret_data);
+}
+
+static int apple_smc_rw_locked(struct apple_smc *smc, smc_key key,
+				const void *wbuf, size_t wsize,
+				void *rbuf, size_t rsize)
+{
+	u64 smc_size, smc_wsize;
+	u32 rdata;
+	int ret;
+	u64 cmd;
+
+	lockdep_assert_held(&smc->mutex);
+
+	if (rsize > SMC_MAX_SIZE)
+		return -EINVAL;
+	if (wsize > SMC_MAX_SIZE)
+		return -EINVAL;
+
+	if (rsize && wsize) {
+		cmd = SMC_MSG_RW_KEY;
+		memcpy_toio(smc->shmem.iomem, wbuf, wsize);
+		smc_size = rsize;
+		smc_wsize = wsize;
+	} else if (wsize && !rsize) {
+		cmd = SMC_MSG_WRITE_KEY;
+		memcpy_toio(smc->shmem.iomem, wbuf, wsize);
+		/*
+		 * Setting size to the length we want to write and wsize to 0
+		 * looks silly but that's how the SMC protocol works ¯\_(ツ)_/¯
+		 */
+		smc_size = wsize;
+		smc_wsize = 0;
+	} else if (!wsize && rsize) {
+		cmd = SMC_MSG_READ_KEY;
+		smc_size = rsize;
+		smc_wsize = 0;
+	} else {
+		return -EINVAL;
+	}
+
+	ret = apple_smc_cmd_locked(smc, cmd, key, smc_size, smc_wsize, &rdata);
+	if (ret < 0)
+		return ret;
+
+	if (rsize) {
+		/*
+		 * Small data <= 4 bytes is returned as part of the reply
+		 * message which is sent over the mailbox FIFO. Everything
+		 * bigger has to be copied from SRAM which is mapped as
+		 * Device memory.
+		 */
+		if (rsize <= 4)
+			memcpy(rbuf, &rdata, rsize);
+		else
+			memcpy_fromio(rbuf, smc->shmem.iomem, rsize);
+	}
+
+	return ret;
+}
+
+int apple_smc_read(struct apple_smc *smc, smc_key key, void *buf, size_t size)
+{
+	guard(mutex)(&smc->mutex);
+
+	return apple_smc_rw_locked(smc, key, NULL, 0, buf, size);
+}
+EXPORT_SYMBOL(apple_smc_read);
+
+int apple_smc_write(struct apple_smc *smc, smc_key key, void *buf, size_t size)
+{
+	guard(mutex)(&smc->mutex);
+
+	return apple_smc_rw_locked(smc, key, buf, size, NULL, 0);
+}
+EXPORT_SYMBOL(apple_smc_write);
+
+int apple_smc_rw(struct apple_smc *smc, smc_key key, void *wbuf, size_t wsize,
+		 void *rbuf, size_t rsize)
+{
+	guard(mutex)(&smc->mutex);
+
+	return apple_smc_rw_locked(smc, key, wbuf, wsize, rbuf, rsize);
+}
+EXPORT_SYMBOL(apple_smc_rw);
+
+int apple_smc_get_key_by_index(struct apple_smc *smc, int index, smc_key *key)
+{
+	int ret;
+
+	ret = apple_smc_cmd(smc, SMC_MSG_GET_KEY_BY_INDEX, index, 0, 0, key);
+
+	*key = swab32(*key);
+	return ret;
+}
+EXPORT_SYMBOL(apple_smc_get_key_by_index);
+
+int apple_smc_get_key_info(struct apple_smc *smc, smc_key key, struct apple_smc_key_info *info)
+{
+	u8 key_info[6];
+	int ret;
+
+	ret = apple_smc_cmd(smc, SMC_MSG_GET_KEY_INFO, key, 0, 0, NULL);
+	if (ret >= 0 && info) {
+		memcpy_fromio(key_info, smc->shmem.iomem, sizeof(key_info));
+		info->size = key_info[0];
+		info->type_code = get_unaligned_be32(&key_info[1]);
+		info->flags = key_info[5];
+	}
+	return ret;
+}
+EXPORT_SYMBOL(apple_smc_get_key_info);
+
+int apple_smc_enter_atomic(struct apple_smc *smc)
+{
+	guard(mutex)(&smc->mutex);
+
+	/*
+	 * Disable notifications since this is called before shutdown and no
+	 * notification handler will be able to handle the notification
+	 * using atomic operations only. Also ignore any failure here
+	 * because we're about to shut down or reboot anyway.
+	 * We can't use apple_smc_write_flag here since that would try to lock
+	 * smc->mutex again.
+	 */
+	const u8 flag = 0;
+
+	apple_smc_rw_locked(smc, SMC_KEY(NTAP), &flag, sizeof(flag), NULL, 0);
+
+	smc->atomic_mode = true;
+
+	return 0;
+}
+EXPORT_SYMBOL(apple_smc_enter_atomic);
+
+int apple_smc_write_atomic(struct apple_smc *smc, smc_key key, void *buf, size_t size)
+{
+	guard(spinlock_irqsave)(&smc->lock);
+	u8 result;
+	int ret;
+	u64 msg;
+
+	if (size > SMC_MAX_SIZE || size == 0)
+		return -EINVAL;
+
+	if (smc->boot_stage != APPLE_SMC_INITIALIZED)
+		return -EIO;
+	if (!smc->atomic_mode)
+		return -EIO;
+
+	memcpy_toio(smc->shmem.iomem, buf, size);
+	smc->msg_id = (smc->msg_id + 1) & 0xf;
+	msg = (FIELD_PREP(SMC_MSG, SMC_MSG_WRITE_KEY) |
+	       FIELD_PREP(SMC_SIZE, size) |
+	       FIELD_PREP(SMC_ID, smc->msg_id) |
+	       FIELD_PREP(SMC_DATA, key));
+	smc->atomic_pending = true;
+
+	ret = apple_rtkit_send_message(smc->rtk, SMC_ENDPOINT, msg, NULL, true);
+	if (ret < 0) {
+		dev_err(smc->dev, "Failed to send command (%d)\n", ret);
+		return ret;
+	}
+
+	while (smc->atomic_pending) {
+		ret = apple_rtkit_poll(smc->rtk);
+		if (ret < 0) {
+			dev_err(smc->dev, "RTKit poll failed (%llx)", msg);
+			return ret;
+		}
+		udelay(100);
+	}
+
+	if (FIELD_GET(SMC_ID, smc->cmd_ret) != smc->msg_id) {
+		dev_err(smc->dev, "Command sequence mismatch (expected %d, got %d)\n",
+			smc->msg_id, (unsigned int)FIELD_GET(SMC_ID, smc->cmd_ret));
+		return -EIO;
+	}
+
+	result = FIELD_GET(SMC_RESULT, smc->cmd_ret);
+	if (result)
+		return -EIO;
+
+	return FIELD_GET(SMC_SIZE, smc->cmd_ret);
+}
+EXPORT_SYMBOL(apple_smc_write_atomic);
+
+static void apple_smc_rtkit_crashed(void *cookie, const void *bfr, size_t bfr_len)
+{
+	struct apple_smc *smc = cookie;
+
+	smc->boot_stage = APPLE_SMC_ERROR_CRASHED;
+	dev_err(smc->dev, "SMC crashed! Your system will reboot in a few seconds...\n");
+}
+
+static int apple_smc_rtkit_shmem_setup(void *cookie, struct apple_rtkit_shmem *bfr)
+{
+	struct apple_smc *smc = cookie;
+	size_t bfr_end;
+
+	if (!bfr->iova) {
+		dev_err(smc->dev, "RTKit wants a RAM buffer\n");
+		return -EIO;
+	}
+
+	if (check_add_overflow(bfr->iova, bfr->size - 1, &bfr_end))
+		return -EFAULT;
+
+	if (bfr->iova < smc->sram->start || bfr->iova > smc->sram->end ||
+	    bfr_end > smc->sram->end) {
+		dev_err(smc->dev, "RTKit buffer request outside SRAM region: [0x%llx, 0x%llx]\n",
+			(unsigned long long)bfr->iova,
+			(unsigned long long)bfr_end);
+		return -EFAULT;
+	}
+
+	bfr->iomem = smc->sram_base + (bfr->iova - smc->sram->start);
+	bfr->is_mapped = true;
+
+	return 0;
+}
+
+static bool apple_smc_rtkit_recv_early(void *cookie, u8 endpoint, u64 message)
+{
+	struct apple_smc *smc = cookie;
+
+	if (endpoint != SMC_ENDPOINT) {
+		dev_warn(smc->dev, "Received message for unknown endpoint 0x%x\n", endpoint);
+		return false;
+	}
+
+	if (smc->boot_stage == APPLE_SMC_BOOTING) {
+		int ret;
+
+		smc->shmem.iova = message;
+		smc->shmem.size = SMC_SHMEM_SIZE;
+		ret = apple_smc_rtkit_shmem_setup(smc, &smc->shmem);
+		if (ret < 0) {
+			smc->boot_stage = APPLE_SMC_ERROR_NO_SHMEM;
+			dev_err(smc->dev, "Failed to initialize shared memory (%d)\n", ret);
+		} else {
+			smc->boot_stage = APPLE_SMC_INITIALIZED;
+		}
+		complete(&smc->init_done);
+	} else if (FIELD_GET(SMC_MSG, message) == SMC_MSG_NOTIFICATION) {
+		/* Handle these in the RTKit worker thread */
+		return false;
+	} else {
+		smc->cmd_ret = message;
+		if (smc->atomic_pending)
+			smc->atomic_pending = false;
+		else
+			complete(&smc->cmd_done);
+	}
+
+	return true;
+}
+
+static void apple_smc_rtkit_recv(void *cookie, u8 endpoint, u64 message)
+{
+	struct apple_smc *smc = cookie;
+
+	if (endpoint != SMC_ENDPOINT) {
+		dev_warn(smc->dev, "Received message for unknown endpoint 0x%x\n", endpoint);
+		return;
+	}
+
+	if (FIELD_GET(SMC_MSG, message) != SMC_MSG_NOTIFICATION) {
+		dev_warn(smc->dev, "Received unknown message from worker: 0x%llx\n", message);
+		return;
+	}
+
+	blocking_notifier_call_chain(&smc->event_handlers, FIELD_GET(SMC_DATA, message), NULL);
+}
+
+static const struct apple_rtkit_ops apple_smc_rtkit_ops = {
+	.crashed = apple_smc_rtkit_crashed,
+	.recv_message = apple_smc_rtkit_recv,
+	.recv_message_early = apple_smc_rtkit_recv_early,
+	.shmem_setup = apple_smc_rtkit_shmem_setup,
+};
+
+static void apple_smc_rtkit_shutdown(void *data)
+{
+	struct apple_smc *smc = data;
+
+	/* Shut down SMC firmware, if it's not completely wedged */
+	if (apple_rtkit_is_running(smc->rtk))
+		apple_rtkit_quiesce(smc->rtk);
+}
+
+static void apple_smc_disable_notifications(void *data)
+{
+	struct apple_smc *smc = data;
+
+	apple_smc_write_flag(smc, SMC_KEY(NTAP), false);
+}
+
+static int apple_smc_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct apple_smc *smc;
+	u32 count;
+	int ret;
+
+	smc = devm_kzalloc(dev, sizeof(*smc), GFP_KERNEL);
+	if (!smc)
+		return -ENOMEM;
+
+	smc->dev = &pdev->dev;
+	smc->sram_base = devm_platform_get_and_ioremap_resource(pdev, 1, &smc->sram);
+	if (IS_ERR(smc->sram_base))
+		return dev_err_probe(dev, PTR_ERR(smc->sram_base), "Failed to map SRAM region");
+
+	smc->rtk = devm_apple_rtkit_init(dev, smc, NULL, 0, &apple_smc_rtkit_ops);
+	if (IS_ERR(smc->rtk))
+		return dev_err_probe(dev, PTR_ERR(smc->rtk), "Failed to initialize RTKit");
+
+	smc->boot_stage = APPLE_SMC_BOOTING;
+	ret = apple_rtkit_wake(smc->rtk);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to wake up SMC");
+
+	ret = devm_add_action_or_reset(dev, apple_smc_rtkit_shutdown, smc);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to register rtkit shutdown action");
+
+	ret = apple_rtkit_start_ep(smc->rtk, SMC_ENDPOINT);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to start SMC endpoint");
+
+	init_completion(&smc->init_done);
+	init_completion(&smc->cmd_done);
+
+	ret = apple_rtkit_send_message(smc->rtk, SMC_ENDPOINT,
+				       FIELD_PREP(SMC_MSG, SMC_MSG_INITIALIZE), NULL, false);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to send init message");
+
+	if (wait_for_completion_timeout(&smc->init_done, msecs_to_jiffies(SMC_TIMEOUT_MS)) == 0) {
+		dev_err(dev, "Timed out initializing SMC");
+		return -ETIMEDOUT;
+	}
+
+	if (smc->boot_stage != APPLE_SMC_INITIALIZED) {
+		dev_err(dev, "SMC failed to boot successfully, boot stage=%d\n", smc->boot_stage);
+		return -EIO;
+	}
+
+	dev_set_drvdata(&pdev->dev, smc);
+	BLOCKING_INIT_NOTIFIER_HEAD(&smc->event_handlers);
+
+	ret = apple_smc_read_u32(smc, SMC_KEY(#KEY), &count);
+	if (ret)
+		return dev_err_probe(smc->dev, ret, "Failed to get key count");
+	smc->key_count = be32_to_cpu(count);
+
+	/* Enable notifications */
+	apple_smc_write_flag(smc, SMC_KEY(NTAP), true);
+	ret = devm_add_action_or_reset(dev, apple_smc_disable_notifications, smc);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to register notification disable action");
+
+	ret = devm_mfd_add_devices(smc->dev, PLATFORM_DEVID_NONE,
+				   apple_smc_devs, ARRAY_SIZE(apple_smc_devs),
+				   NULL, 0, NULL);
+	if (ret)
+		return dev_err_probe(smc->dev, ret, "Failed to register sub-devices");
+
+
+	return 0;
+}
+
+static const struct of_device_id apple_smc_of_match[] = {
+	{ .compatible = "apple,smc" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, apple_smc_of_match);
+
+static struct platform_driver apple_smc_driver = {
+	.driver = {
+		.name = "macsmc",
+		.of_match_table = apple_smc_of_match,
+	},
+	.probe = apple_smc_probe,
+};
+module_platform_driver(apple_smc_driver);
+
+MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
+MODULE_AUTHOR("Sven Peter <sven@kernel.org>");
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_DESCRIPTION("Apple SMC driver");
diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index e71f0af4e378c1..733d812621599d 100644
--- a/drivers/power/reset/Kconfig
+++ b/drivers/power/reset/Kconfig
@@ -128,6 +128,15 @@ config POWER_RESET_LINKSTATION
 
 	  Say Y here if you have a Buffalo LinkStation LS421D/E.
 
+config POWER_RESET_MACSMC
+	tristate "Apple SMC reset/power-off driver"
+	depends on MFD_MACSMC
+	help
+	  This driver supports reset and power-off on Apple Mac machines
+	  that implement this functionality via the SMC.
+
+	  Say Y here if you have an Apple Silicon Mac.
+
 config POWER_RESET_MSM
 	bool "Qualcomm MSM power-off driver"
 	depends on ARCH_QCOM
diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
index 1b9b63a1a8731b..b7c2b5940be997 100644
--- a/drivers/power/reset/Makefile
+++ b/drivers/power/reset/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_POWER_RESET_GPIO) += gpio-poweroff.o
 obj-$(CONFIG_POWER_RESET_GPIO_RESTART) += gpio-restart.o
 obj-$(CONFIG_POWER_RESET_HISI) += hisi-reboot.o
 obj-$(CONFIG_POWER_RESET_LINKSTATION) += linkstation-poweroff.o
+obj-$(CONFIG_POWER_RESET_MACSMC) += macsmc-reboot.o
 obj-$(CONFIG_POWER_RESET_MSM) += msm-poweroff.o
 obj-$(CONFIG_POWER_RESET_MT6323) += mt6323-poweroff.o
 obj-$(CONFIG_POWER_RESET_QCOM_PON) += qcom-pon.o
diff --git a/drivers/power/reset/macsmc-reboot.c b/drivers/power/reset/macsmc-reboot.c
new file mode 100644
index 00000000000000..e9702acdd366b0
--- /dev/null
+++ b/drivers/power/reset/macsmc-reboot.c
@@ -0,0 +1,290 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SMC Reboot/Poweroff Handler
+ * Copyright The Asahi Linux Contributors
+ */
+
+#include <linux/delay.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/macsmc.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/slab.h>
+
+struct macsmc_reboot_nvmem {
+	struct nvmem_cell *shutdown_flag;
+	struct nvmem_cell *boot_stage;
+	struct nvmem_cell *boot_error_count;
+	struct nvmem_cell *panic_count;
+};
+
+static const char * const nvmem_names[] = {
+	"shutdown_flag",
+	"boot_stage",
+	"boot_error_count",
+	"panic_count",
+};
+
+enum boot_stage {
+	BOOT_STAGE_SHUTDOWN		= 0x00, /* Clean shutdown */
+	BOOT_STAGE_IBOOT_DONE		= 0x2f, /* Last stage of bootloader */
+	BOOT_STAGE_KERNEL_STARTED	= 0x30, /* Normal OS booting */
+};
+
+struct macsmc_reboot {
+	struct device *dev;
+	struct apple_smc *smc;
+	struct notifier_block reboot_notify;
+
+	union {
+		struct macsmc_reboot_nvmem nvm;
+		struct nvmem_cell *nvm_cells[ARRAY_SIZE(nvmem_names)];
+	};
+};
+
+/* Helpers to read/write a u8 given a struct nvmem_cell */
+static int nvmem_cell_get_u8(struct nvmem_cell *cell)
+{
+	size_t len;
+	void *bfr;
+	u8 val;
+
+	bfr = nvmem_cell_read(cell, &len);
+	if (IS_ERR(bfr))
+		return PTR_ERR(bfr);
+
+	if (len < 1) {
+		kfree(bfr);
+		return -EINVAL;
+	}
+
+	val = *(u8 *)bfr;
+	kfree(bfr);
+	return val;
+}
+
+static int nvmem_cell_set_u8(struct nvmem_cell *cell, u8 val)
+{
+	return nvmem_cell_write(cell, &val, sizeof(val));
+}
+
+/*
+ * SMC 'MBSE' key actions:
+ *
+ * 'offw' - shutdown warning
+ * 'slpw' - sleep warning
+ * 'rest' - restart warning
+ * 'off1' - shutdown (needs PMU bit set to stay on)
+ * 'susp' - suspend
+ * 'phra' - restart ("PE Halt Restart Action"?)
+ * 'panb' - panic beginning
+ * 'pane' - panic end
+ */
+
+static int macsmc_prepare_atomic(struct sys_off_data *data)
+{
+	struct macsmc_reboot *reboot = data->cb_data;
+
+	dev_info(reboot->dev, "Preparing SMC for atomic mode\n");
+
+	apple_smc_enter_atomic(reboot->smc);
+	return NOTIFY_OK;
+}
+
+static int macsmc_power_off(struct sys_off_data *data)
+{
+	struct macsmc_reboot *reboot = data->cb_data;
+
+	dev_info(reboot->dev, "Issuing power off (off1)\n");
+
+	if (apple_smc_write_u32_atomic(reboot->smc, SMC_KEY(MBSE), SMC_KEY(off1)) < 0) {
+		dev_err(reboot->dev, "Failed to issue MBSE = off1 (power_off)\n");
+	} else {
+		mdelay(100);
+		WARN_ONCE(1, "Unable to power off system\n");
+	}
+
+	return NOTIFY_OK;
+}
+
+static int macsmc_restart(struct sys_off_data *data)
+{
+	struct macsmc_reboot *reboot = data->cb_data;
+
+	dev_info(reboot->dev, "Issuing restart (phra)\n");
+
+	if (apple_smc_write_u32_atomic(reboot->smc, SMC_KEY(MBSE), SMC_KEY(phra)) < 0) {
+		dev_err(reboot->dev, "Failed to issue MBSE = phra (restart)\n");
+	} else {
+		mdelay(100);
+		WARN_ONCE(1, "Unable to restart system\n");
+	}
+
+	return NOTIFY_OK;
+}
+
+static int macsmc_reboot_notify(struct notifier_block *this, unsigned long action, void *data)
+{
+	struct macsmc_reboot *reboot = container_of(this, struct macsmc_reboot, reboot_notify);
+	u8 shutdown_flag;
+	u32 val;
+
+	switch (action) {
+	case SYS_RESTART:
+		val = SMC_KEY(rest);
+		shutdown_flag = 0;
+		break;
+	case SYS_POWER_OFF:
+		val = SMC_KEY(offw);
+		shutdown_flag = 1;
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
+
+	dev_info(reboot->dev, "Preparing for reboot (%p4ch)\n", &val);
+
+	/* On the Mac Mini, this will turn off the LED for power off */
+	if (apple_smc_write_u32(reboot->smc, SMC_KEY(MBSE), val) < 0)
+		dev_err(reboot->dev, "Failed to issue MBSE = %p4ch (reboot_prepare)\n", &val);
+
+	/* Set the boot_stage to 0, which means we're doing a clean shutdown/reboot. */
+	if (reboot->nvm.boot_stage &&
+	    nvmem_cell_set_u8(reboot->nvm.boot_stage, BOOT_STAGE_SHUTDOWN) < 0)
+		dev_err(reboot->dev, "Failed to write boot_stage\n");
+
+	/*
+	 * Set the PMU flag to actually reboot into the off state.
+	 * Without this, the device will just reboot. We make it optional in case it is no longer
+	 * necessary on newer hardware.
+	 */
+	if (reboot->nvm.shutdown_flag &&
+	    nvmem_cell_set_u8(reboot->nvm.shutdown_flag, shutdown_flag) < 0)
+		dev_err(reboot->dev, "Failed to write shutdown_flag\n");
+
+	return NOTIFY_OK;
+}
+
+static void macsmc_power_init_error_counts(struct macsmc_reboot *reboot)
+{
+	int boot_error_count, panic_count;
+
+	if (!reboot->nvm.boot_error_count || !reboot->nvm.panic_count)
+		return;
+
+	boot_error_count = nvmem_cell_get_u8(reboot->nvm.boot_error_count);
+	if (boot_error_count < 0) {
+		dev_err(reboot->dev, "Failed to read boot_error_count (%d)\n", boot_error_count);
+		return;
+	}
+
+	panic_count = nvmem_cell_get_u8(reboot->nvm.panic_count);
+	if (panic_count < 0) {
+		dev_err(reboot->dev, "Failed to read panic_count (%d)\n", panic_count);
+		return;
+	}
+
+	if (!boot_error_count && !panic_count)
+		return;
+
+	dev_warn(reboot->dev, "PMU logged %d boot error(s) and %d panic(s)\n",
+		 boot_error_count, panic_count);
+
+	if (nvmem_cell_set_u8(reboot->nvm.panic_count, 0) < 0)
+		dev_err(reboot->dev, "Failed to reset panic_count\n");
+	if (nvmem_cell_set_u8(reboot->nvm.boot_error_count, 0) < 0)
+		dev_err(reboot->dev, "Failed to reset boot_error_count\n");
+}
+
+static int macsmc_reboot_probe(struct platform_device *pdev)
+{
+	struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
+	struct macsmc_reboot *reboot;
+	int ret, i;
+
+	reboot = devm_kzalloc(&pdev->dev, sizeof(*reboot), GFP_KERNEL);
+	if (!reboot)
+		return -ENOMEM;
+
+	reboot->dev = &pdev->dev;
+	reboot->smc = smc;
+
+	platform_set_drvdata(pdev, reboot);
+
+	for (i = 0; i < ARRAY_SIZE(nvmem_names); i++) {
+		struct nvmem_cell *cell;
+
+		cell = devm_nvmem_cell_get(&pdev->dev,
+					   nvmem_names[i]);
+		if (IS_ERR(cell)) {
+			if (PTR_ERR(cell) == -EPROBE_DEFER)
+				return -EPROBE_DEFER;
+			dev_warn(&pdev->dev, "Missing NVMEM cell %s (%ld)\n",
+				 nvmem_names[i], PTR_ERR(cell));
+			/* Non fatal, we'll deal with it */
+			cell = NULL;
+		}
+		reboot->nvm_cells[i] = cell;
+	}
+
+	/* Set the boot_stage to indicate we're running the OS kernel */
+	if (reboot->nvm.boot_stage &&
+	    nvmem_cell_set_u8(reboot->nvm.boot_stage, BOOT_STAGE_KERNEL_STARTED) < 0)
+		dev_err(reboot->dev, "Failed to write boot_stage\n");
+
+	/* Display and clear the error counts */
+	macsmc_power_init_error_counts(reboot);
+
+	reboot->reboot_notify.notifier_call = macsmc_reboot_notify;
+
+	ret = devm_register_sys_off_handler(&pdev->dev, SYS_OFF_MODE_POWER_OFF_PREPARE,
+					    SYS_OFF_PRIO_HIGH, macsmc_prepare_atomic, reboot);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret,
+				     "Failed to register power-off prepare handler\n");
+	ret = devm_register_sys_off_handler(&pdev->dev, SYS_OFF_MODE_POWER_OFF, SYS_OFF_PRIO_HIGH,
+					    macsmc_power_off, reboot);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret,
+				     "Failed to register power-off handler\n");
+
+	ret = devm_register_sys_off_handler(&pdev->dev, SYS_OFF_MODE_RESTART_PREPARE,
+					    SYS_OFF_PRIO_HIGH, macsmc_prepare_atomic, reboot);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret,
+				     "Failed to register restart prepare handler\n");
+	ret = devm_register_sys_off_handler(&pdev->dev, SYS_OFF_MODE_RESTART, SYS_OFF_PRIO_HIGH,
+					    macsmc_restart, reboot);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret, "Failed to register restart handler\n");
+
+	ret = devm_register_reboot_notifier(&pdev->dev, &reboot->reboot_notify);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret, "Failed to register reboot notifier\n");
+
+	dev_info(&pdev->dev, "Handling reboot and poweroff requests via SMC\n");
+
+	return 0;
+}
+
+static const struct of_device_id macsmc_reboot_of_table[] = {
+	{ .compatible = "apple,smc-reboot", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, macsmc_reboot_of_table);
+
+static struct platform_driver macsmc_reboot_driver = {
+	.driver = {
+		.name = "macsmc-reboot",
+		.of_match_table = macsmc_reboot_of_table,
+	},
+	.probe = macsmc_reboot_probe,
+};
+module_platform_driver(macsmc_reboot_driver);
+
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_DESCRIPTION("Apple SMC reboot/poweroff driver");
+MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
diff --git a/drivers/soc/apple/rtkit.c b/drivers/soc/apple/rtkit.c
index 5fffd0f003dc2f..b8d4da147d23f7 100644
--- a/drivers/soc/apple/rtkit.c
+++ b/drivers/soc/apple/rtkit.c
@@ -279,8 +279,7 @@ static int apple_rtkit_common_rx_get_buffer(struct apple_rtkit *rtk,
 	dev_dbg(rtk->dev, "RTKit: buffer request for 0x%zx bytes at %pad\n",
 		buffer->size, &buffer->iova);
 
-	if (buffer->iova &&
-	    (!rtk->ops->shmem_setup || !rtk->ops->shmem_destroy)) {
+	if (buffer->iova && !rtk->ops->shmem_setup) {
 		err = -EINVAL;
 		goto error;
 	}
diff --git a/include/linux/mfd/macsmc.h b/include/linux/mfd/macsmc.h
new file mode 100644
index 00000000000000..6b13f01a85924f
--- /dev/null
+++ b/include/linux/mfd/macsmc.h
@@ -0,0 +1,279 @@
+/* SPDX-License-Identifier: GPL-2.0-only OR MIT */
+/*
+ * Apple SMC (System Management Controller) core definitions
+ *
+ * Copyright (C) The Asahi Linux Contributors
+ */
+
+#ifndef _LINUX_MFD_MACSMC_H
+#define _LINUX_MFD_MACSMC_H
+
+#include <linux/soc/apple/rtkit.h>
+
+/**
+ * typedef smc_key - Alias for u32 to be used for SMC keys
+ *
+ * SMC keys are 32bit integers containing packed ASCII characters in natural
+ * integer order, i.e. 0xAABBCCDD, which represent the FourCC ABCD.
+ * The SMC driver is designed with this assumption and ensures the right
+ * endianness is used when these are stored to memory and sent to or received
+ * from the actual SMC firmware (which can be done in either shared memory or
+ * as 64bit mailbox message on Apple Silicon).
+ * Internally, SMC stores these keys in a table sorted lexicographically and
+ * allows resolving an index into this table to the corresponding SMC key.
+ * Thus, storing keys as u32 is very convenient as it allows to e.g. use
+ * normal comparison operators which directly map to the natural order used
+ * by SMC firmware.
+ *
+ * This simple type alias is introduced to allow easy recognition of SMC key
+ * variables and arguments.
+ */
+typedef u32 smc_key;
+
+/**
+ * SMC_KEY - Convert FourCC SMC keys in source code to smc_key
+ *
+ * This macro can be used to easily define FourCC SMC keys in source code
+ * and convert these to u32 / smc_key, e.g. SMC_KEY(NTAP) will expand to
+ * 0x4e544150.
+ *
+ * @s: FourCC SMC key to be converted
+ */
+#define SMC_KEY(s) (smc_key)(_SMC_KEY(#s))
+#define _SMC_KEY(s) (((s)[0] << 24) | ((s)[1] << 16) | ((s)[2] << 8) | (s)[3])
+
+#define APPLE_SMC_READABLE BIT(7)
+#define APPLE_SMC_WRITABLE BIT(6)
+#define APPLE_SMC_FUNCTION BIT(4)
+
+/**
+ * struct apple_smc_key_info - Information for a SMC key as returned by SMC
+ * @type_code: FourCC code indicating the type for this key.
+ *             Known types:
+ *              ch8*: ASCII string
+ *              flag: Boolean, 1 or 0
+ *              flt: 32-bit single-precision IEEE 754 float
+ *              hex: Binary data
+ *              ioft: 64bit Unsigned fixed-point intger (48.16)
+ *              {si,ui}{8,16,32,64}: Signed/Unsigned 8-/16-/32-/64-bit integer
+ * @size: Size of the buffer associated with this key
+ * @flags: Bitfield encoding flags (APPLE_SMC_{READABLE,WRITABLE,FUNCTION})
+ */
+struct apple_smc_key_info {
+	u32 type_code;
+	u8 size;
+	u8 flags;
+};
+
+/**
+ * enum apple_smc_boot_stage - SMC boot stage
+ * @APPLE_SMC_BOOTING: SMC is booting
+ * @APPLE_SMC_INITIALIZED: SMC is initialized and ready to use
+ * @APPLE_SMC_ERROR_NO_SHMEM: Shared memory could not be initialized during boot
+ * @APPLE_SMC_ERROR_CRASHED: SMC has crashed
+ */
+enum apple_smc_boot_stage {
+	APPLE_SMC_BOOTING,
+	APPLE_SMC_INITIALIZED,
+	APPLE_SMC_ERROR_NO_SHMEM,
+	APPLE_SMC_ERROR_CRASHED
+};
+
+/**
+ * struct apple_smc
+ * @dev: Underlying device struct for the physical backend device
+ * @key_count: Number of available SMC keys
+ * @first_key: First valid SMC key
+ * @last_key: Last valid SMC key
+ * @event_handlers: Notifier call chain for events received from SMC
+ * @rtk: Pointer to Apple RTKit instance
+ * @init_done: Completion for initialization
+ * @boot_stage: Current boot stage of SMC
+ * @sram: Pointer to SRAM resource
+ * @sram_base: SRAM base address
+ * @shmem: RTKit shared memory structure for SRAM
+ * @msg_id: Current message id for commands, will be incremented for each command
+ * @atomic_mode: Flag set when atomic mode is entered
+ * @atomic_pending: Flag indicating pending atomic command
+ * @cmd_done: Completion for command execution in non-atomic mode
+ * @cmd_ret: Return value from SMC for last command
+ * @mutex: Mutex for non-atomic mode
+ * @lock: Spinlock for atomic mode
+ */
+struct apple_smc {
+	struct device *dev;
+
+	u32 key_count;
+	smc_key first_key;
+	smc_key last_key;
+
+	struct blocking_notifier_head event_handlers;
+
+	struct apple_rtkit *rtk;
+
+	struct completion init_done;
+	enum apple_smc_boot_stage boot_stage;
+
+	struct resource *sram;
+	void __iomem *sram_base;
+	struct apple_rtkit_shmem shmem;
+
+	unsigned int msg_id;
+
+	bool atomic_mode;
+	bool atomic_pending;
+	struct completion cmd_done;
+	u64 cmd_ret;
+
+	struct mutex mutex;
+	spinlock_t lock;
+};
+
+/**
+ * apple_smc_read - Read size bytes from given SMC key into buf
+ * @smc: Pointer to apple_smc struct
+ * @key: smc_key to be read
+ * @buf: Buffer into which size bytes of data will be read from SMC
+ * @size: Number of bytes to be read into buf
+ *
+ * Return: Zero on success, negative errno on error
+ */
+int apple_smc_read(struct apple_smc *smc, smc_key key, void *buf, size_t size);
+
+/**
+ * apple_smc_write - Write size bytes into given SMC key from buf
+ * @smc: Pointer to apple_smc struct
+ * @key: smc_key data will be written to
+ * @buf: Buffer from which size bytes of data will be written to SMC
+ * @size: Number of bytes to be written
+ *
+ * Return: Zero on success, negative errno on error
+ */
+int apple_smc_write(struct apple_smc *smc, smc_key key, void *buf, size_t size);
+
+/**
+ * apple_smc_enter_atomic - Enter atomic mode to be able to use apple_smc_write_atomic
+ * @smc: Pointer to apple_smc struct
+ *
+ * This function switches the SMC backend to atomic mode which allows the
+ * use of apple_smc_write_atomic while disabling *all* other functions.
+ * This is only used for shutdown/reboot which requires writing to a SMC
+ * key from atomic context.
+ *
+ * Return: Zero on success, negative errno on error
+ */
+int apple_smc_enter_atomic(struct apple_smc *smc);
+
+/**
+ * apple_smc_write_atomic - Write size bytes into given SMC key from buf without sleeping
+ * @smc: Pointer to apple_smc struct
+ * @key: smc_key data will be written to
+ * @buf: Buffer from which size bytes of data will be written to SMC
+ * @size: Number of bytes to be written
+ *
+ * Note that this function will fail if apple_smc_enter_atomic hasn't been
+ * called before.
+ *
+ * Return: Zero on success, negative errno on error
+ */
+int apple_smc_write_atomic(struct apple_smc *smc, smc_key key, void *buf, size_t size);
+
+/**
+ * apple_smc_rw - Write and then read using the given SMC key
+ * @smc: Pointer to apple_smc struct
+ * @key: smc_key data will be written to
+ * @wbuf: Buffer from which size bytes of data will be written to SMC
+ * @wsize: Number of bytes to be written
+ * @rbuf: Buffer to which size bytes of data will be read from SMC
+ * @rsize: Number of bytes to be read
+ *
+ * Return: Zero on success, negative errno on error
+ */
+int apple_smc_rw(struct apple_smc *smc, smc_key key, void *wbuf, size_t wsize,
+		 void *rbuf, size_t rsize);
+
+/**
+ * apple_smc_get_key_by_index - Given an index return the corresponding SMC key
+ * @smc: Pointer to apple_smc struct
+ * @index: Index to be resolved
+ * @key: Buffer for SMC key to be returned
+ *
+ * Return: Zero on success, negative errno on error
+ */
+int apple_smc_get_key_by_index(struct apple_smc *smc, int index, smc_key *key);
+
+/**
+ * apple_smc_get_key_info - Get key information from SMC
+ * @smc: Pointer to apple_smc struct
+ * @key: Key to acquire information for
+ * @info: Pointer to struct apple_smc_key_info which will be filled
+ *
+ * Return: Zero on success, negative errno on error
+ */
+int apple_smc_get_key_info(struct apple_smc *smc, smc_key key, struct apple_smc_key_info *info);
+
+/**
+ * apple_smc_key_exists - Check if the given SMC key exists
+ * @smc: Pointer to apple_smc struct
+ * @key: smc_key to be checked
+ *
+ * Return: True if the key exists, false otherwise
+ */
+static inline bool apple_smc_key_exists(struct apple_smc *smc, smc_key key)
+{
+	return apple_smc_get_key_info(smc, key, NULL) >= 0;
+}
+
+#define APPLE_SMC_TYPE_OPS(type) \
+	static inline int apple_smc_read_##type(struct apple_smc *smc, smc_key key, type *p) \
+	{ \
+		int ret = apple_smc_read(smc, key, p, sizeof(*p)); \
+		return (ret < 0) ? ret : ((ret != sizeof(*p)) ? -EINVAL : 0); \
+	} \
+	static inline int apple_smc_write_##type(struct apple_smc *smc, smc_key key, type p) \
+	{ \
+		return apple_smc_write(smc, key, &p, sizeof(p)); \
+	} \
+	static inline int apple_smc_write_##type##_atomic(struct apple_smc *smc, smc_key key, type p) \
+	{ \
+		return apple_smc_write_atomic(smc, key, &p, sizeof(p)); \
+	} \
+	static inline int apple_smc_rw_##type(struct apple_smc *smc, smc_key key, \
+					      type w, type *r) \
+	{ \
+		int ret = apple_smc_rw(smc, key, &w, sizeof(w), r, sizeof(*r)); \
+		return (ret < 0) ? ret : ((ret != sizeof(*r)) ? -EINVAL : 0); \
+	}
+
+APPLE_SMC_TYPE_OPS(u64)
+APPLE_SMC_TYPE_OPS(u32)
+APPLE_SMC_TYPE_OPS(u16)
+APPLE_SMC_TYPE_OPS(u8)
+APPLE_SMC_TYPE_OPS(s64)
+APPLE_SMC_TYPE_OPS(s32)
+APPLE_SMC_TYPE_OPS(s16)
+APPLE_SMC_TYPE_OPS(s8)
+
+static inline int apple_smc_read_flag(struct apple_smc *smc, smc_key key, bool *flag)
+{
+	u8 val;
+	int ret = apple_smc_read_u8(smc, key, &val);
+
+	if (ret < 0)
+		return ret;
+
+	*flag = val ? true : false;
+	return ret;
+}
+
+static inline int apple_smc_write_flag(struct apple_smc *smc, smc_key key, bool state)
+{
+	return apple_smc_write_u8(smc, key, state ? 1 : 0);
+}
+
+static inline int apple_smc_write_flag_atomic(struct apple_smc *smc, smc_key key, bool state)
+{
+	return apple_smc_write_u8_atomic(smc, key, state ? 1 : 0);
+}
+
+#endif