Re: [PATCH v5 07/10] power: reset: macsmc-reboot: Add driver for rebooting via Apple SMC

[Alyssa Rosenzweig <alyssa@rosenzweig.io>]

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>

with Stefan's comment addressed

Le Sun , May 11, 2025 at 08:18:42AM +0000, Sven Peter via B4 Relay a écrit :
> From: Hector Martin <marcan@marcan.st>
> 
> This driver implements the reboot/shutdown support exposed by the SMC
> on Apple Silicon machines, such as Apple M1 Macs.
> 
> Signed-off-by: Hector Martin <marcan@marcan.st>
> Signed-off-by: Sven Peter <sven@svenpeter.dev>
> ---
>  MAINTAINERS                         |   1 +
>  drivers/power/reset/Kconfig         |  11 ++
>  drivers/power/reset/Makefile        |   1 +
>  drivers/power/reset/macsmc-reboot.c | 363 ++++++++++++++++++++++++++++++++++++
>  4 files changed, 376 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index fa3a5f9ee40446bcc725c9eac2a36651e6bc7553..84f7a730eb2260b7c1e0487d18c8eb3de82f5206 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2303,6 +2303,7 @@ F:	drivers/mfd/macsmc.c
>  F:	drivers/nvme/host/apple.c
>  F:	drivers/nvmem/apple-efuses.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
> diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
> index 60bf0ca64cf395cd18238fc626611c74d29844ee..6e8dfff64fdc001d09b6c00630cd8b7e2fafdd8e 100644
> --- a/drivers/power/reset/Kconfig
> +++ b/drivers/power/reset/Kconfig
> @@ -128,6 +128,17 @@ 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 ARCH_APPLE || COMPILE_TEST
> +	depends on MFD_MACSMC
> +	depends on OF
> +	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 10782d32e1da39f4b8b4566e8a885f2e13f65130..887dd9e49b7293b69b9429ddc0c1571194a153cf 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 0000000000000000000000000000000000000000..d82339e427886667be4ad2de0d1d5c04d2383059
> --- /dev/null
> +++ b/drivers/power/reset/macsmc-reboot.c
> @@ -0,0 +1,363 @@
> +// 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/module.h>
> +#include <linux/nvmem-consumer.h>
> +#include <linux/of.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 *pm_setting;
> +	struct nvmem_cell *boot_stage;
> +	struct nvmem_cell *boot_error_count;
> +	struct nvmem_cell *panic_count;
> +};
> +
> +static const char * const nvmem_names[] = {
> +	"shutdown_flag",
> +	"pm_setting",
> +	"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 */
> +};
> +
> +enum pm_setting {
> +	PM_SETTING_AC_POWER_RESTORE	= 0x02,
> +	PM_SETTING_AC_POWER_OFF		= 0x03,
> +};
> +
> +static const char * const ac_power_modes[] = { "off", "restore" };
> +
> +static int ac_power_mode_map[] = {
> +	PM_SETTING_AC_POWER_OFF,
> +	PM_SETTING_AC_POWER_RESTORE,
> +};
> +
> +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;
> +	u8 val;
> +	void *ret = nvmem_cell_read(cell, &len);
> +
> +	if (IS_ERR(ret))
> +		return PTR_ERR(ret);
> +
> +	if (len < 1) {
> +		kfree(ret);
> +		return -EINVAL;
> +	}
> +
> +	val = *(u8 *)ret;
> +	kfree(ret);
> +	return val;
> +}
> +
> +static int nvmem_cell_set_u8(struct nvmem_cell *cell, u8 val)
> +{
> +	return nvmem_cell_write(cell, &val, sizeof(val));
> +}
> +
> +static ssize_t macsmc_ac_power_mode_store(struct device *dev, struct device_attribute *attr,
> +					  const char *buf, size_t n)
> +{
> +	struct macsmc_reboot *reboot = dev_get_drvdata(dev);
> +	int mode;
> +	int ret;
> +
> +	mode = sysfs_match_string(ac_power_modes, buf);
> +	if (mode < 0)
> +		return mode;
> +
> +	ret = nvmem_cell_set_u8(reboot->nvm.pm_setting, ac_power_mode_map[mode]);
> +	if (ret < 0)
> +		return ret;
> +
> +	return n;
> +}
> +
> +static ssize_t macsmc_ac_power_mode_show(struct device *dev,
> +					 struct device_attribute *attr, char *buf)
> +{
> +	struct macsmc_reboot *reboot = dev_get_drvdata(dev);
> +	int len = 0;
> +	int i;
> +	int mode = nvmem_cell_get_u8(reboot->nvm.pm_setting);
> +
> +	if (mode < 0)
> +		return mode;
> +
> +	for (i = 0; i < ARRAY_SIZE(ac_power_mode_map); i++) {
> +		if (mode == ac_power_mode_map[i])
> +			len += scnprintf(buf+len, PAGE_SIZE-len,
> +					 "[%s] ", ac_power_modes[i]);
> +		else
> +			len += scnprintf(buf+len, PAGE_SIZE-len,
> +					 "%s ", ac_power_modes[i]);
> +	}
> +
> +	buf[len-1] = '\n';
> +	return len;
> +}
> +static DEVICE_ATTR(ac_power_mode, 0644, macsmc_ac_power_mode_show,
> +		   macsmc_ac_power_mode_store);
> +
> +/*
> + * 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);
> +	u32 val;
> +	u8 shutdown_flag;
> +
> +	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;
> +
> +	/* Ignore devices without this functionality */
> +	if (!apple_smc_key_exists(smc, SMC_KEY(MBSE)))
> +		return -ENODEV;
> +
> +	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);
> +
> +	pdev->dev.of_node = of_get_child_by_name(pdev->dev.parent->of_node, "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");
> +
> +	if (device_create_file(&pdev->dev, &dev_attr_ac_power_mode))
> +		dev_warn(&pdev->dev, "could not create sysfs file\n");
> +
> +	return 0;
> +}
> +
> +static void macsmc_reboot_remove(struct platform_device *pdev)
> +{
> +	device_remove_file(&pdev->dev, &dev_attr_ac_power_mode);
> +}
> +
> +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,
> +	.remove = macsmc_reboot_remove,
> +};
> +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>");
> +MODULE_ALIAS("platform:macsmc-reboot");
> 
> -- 
> 2.34.1
> 
>