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

From: Hector Martin <redacted>

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 <redacted>
Signed-off-by: Sven Peter <redacted>
---
  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);