[PATCH v4] power: reset: Add Spreadtrum SC27xx PMIC power off support

[Baolin Wang]

On Spreadtrum platform, we need power off system through external SC27xx
series PMICs including the SC2720, SC2721, SC2723, SC2730 and SC2731 chips.
Thus this patch adds SC27xx series PMICs power-off support.

Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
---
Changes since v3:
 - Add CONFIG_PM_SLEEP_SMP macro to avoid building error.

Changes since v2:
 - Change to build-in this driver.

Changes since v1:
 - Add remove interface.
 - Add regmap checking when probing the driver.
 - Add MODULE_ALIAS()
---
 drivers/power/reset/Kconfig           |    9 +++++
 drivers/power/reset/Makefile          |    1 +
 drivers/power/reset/sc27xx-poweroff.c |   66 +++++++++++++++++++++++++++++++++
 3 files changed, 76 insertions(+)
 create mode 100644 drivers/power/reset/sc27xx-poweroff.c

diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index ca0de1a..01543f5 100644
--- a/drivers/power/reset/Kconfig
+++ b/drivers/power/reset/Kconfig
@@ -227,5 +227,14 @@ config SYSCON_REBOOT_MODE
 	  register, then the bootloader can read it to take different
 	  action according to the mode.
 
+config POWER_RESET_SC27XX
+	bool "Spreadtrum SC27xx PMIC power-off driver"
+	depends on MFD_SC27XX_PMIC || COMPILE_TEST
+	help
+	  This driver supports powering off a system through
+	  Spreadtrum SC27xx series PMICs. The SC27xx series
+	  PMICs includes the SC2720, SC2721, SC2723, SC2730
+	  and SC2731 chips.
+
 endif
 
diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
index aeb65ed..225d645 100644
--- a/drivers/power/reset/Makefile
+++ b/drivers/power/reset/Makefile
@@ -27,3 +27,4 @@ obj-$(CONFIG_POWER_RESET_RMOBILE) += rmobile-reset.o
 obj-$(CONFIG_POWER_RESET_ZX) += zx-reboot.o
 obj-$(CONFIG_REBOOT_MODE) += reboot-mode.o
 obj-$(CONFIG_SYSCON_REBOOT_MODE) += syscon-reboot-mode.o
+obj-$(CONFIG_POWER_RESET_SC27XX) += sc27xx-poweroff.o
diff --git a/drivers/power/reset/sc27xx-poweroff.c b/drivers/power/reset/sc27xx-poweroff.c
new file mode 100644
index 0000000..65c477e
--- /dev/null
+++ b/drivers/power/reset/sc27xx-poweroff.c
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018 Spreadtrum Communications Inc.
+ * Copyright (C) 2018 Linaro Ltd.
+ */
+
+#include <linux/cpu.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/regmap.h>
+#include <linux/syscore_ops.h>
+
+#define SC27XX_PWR_PD_HW	0xc2c
+#define SC27XX_PWR_OFF_EN	BIT(0)
+
+static struct regmap *regmap;
+
+/*
+ * On Spreadtrum platform, we need power off system through external SC27xx
+ * series PMICs, and it is one similar SPI bus mapped by regmap to access PMIC,
+ * which is not fast io access.
+ *
+ * So before stopping other cores, we need release other cores' resource by
+ * taking cpus down to avoid racing regmap or spi mutex lock when poweroff
+ * system through PMIC.
+ */
+void sc27xx_poweroff_shutdown(void)
+{
+#ifdef CONFIG_PM_SLEEP_SMP
+	int cpu = smp_processor_id();
+
+	freeze_secondary_cpus(cpu);
+#endif
+}
+
+static struct syscore_ops poweroff_syscore_ops = {
+	.shutdown = sc27xx_poweroff_shutdown,
+};
+
+static void sc27xx_poweroff_do_poweroff(void)
+{
+	regmap_write(regmap, SC27XX_PWR_PD_HW, SC27XX_PWR_OFF_EN);
+}
+
+static int sc27xx_poweroff_probe(struct platform_device *pdev)
+{
+	if (regmap)
+		return -EINVAL;
+
+	regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!regmap)
+		return -ENODEV;
+
+	pm_power_off = sc27xx_poweroff_do_poweroff;
+	register_syscore_ops(&poweroff_syscore_ops);
+	return 0;
+}
+
+static struct platform_driver sc27xx_poweroff_driver = {
+	.probe = sc27xx_poweroff_probe,
+	.driver = {
+		.name = "sc27xx-poweroff",
+	},
+};
+builtin_platform_driver(sc27xx_poweroff_driver);
-- 
1.7.9.5