[PATCH v2 15/17] power: reset: mt6323: add a driver for MT6323 power controller

[sean.wang]

From: Sean Wang <sean.wang@xxxxxxxxxxxx>

The power device is responsible for externally down or up the power
of the remote MediaTek SoC through the tiny circuit BBPU inside PMIC RTC.

Though it's a part of RTC device, it would be better to be a standalone
driver than to be a part of existent RTC driver so as to let us make
concentration on works about power-controlling topic and to obtain
improvements while the subsystem power/reset constantly growing.

Currently, the most basic functionality supported is to just power off
the system by writing to a special bit field in BBPU register after the
system has reached pm_poweroff.

Signed-off-by: Sean Wang <sean.wang@xxxxxxxxxxxx>
---
 drivers/power/reset/Kconfig           | 10 ++++
 drivers/power/reset/Makefile          |  1 +
 drivers/power/reset/mt6323-poweroff.c | 97 +++++++++++++++++++++++++++++++++++
 include/linux/mfd/mt6397/rtc.h        |  1 +
 4 files changed, 109 insertions(+)
 create mode 100644 drivers/power/reset/mt6323-poweroff.c

diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index df58fc8..7b49d71 100644
--- a/drivers/power/reset/Kconfig
+++ b/drivers/power/reset/Kconfig
@@ -128,6 +128,16 @@ config POWER_RESET_LTC2952
 	  This driver supports an external powerdown trigger and board power
 	  down via the LTC2952. Bindings are made in the device tree.
 
+config POWER_RESET_MT6323
+	bool "MediaTek MT6323 power-off driver"
+	depends on MFD_MT6397
+	help
+	  The power-off driver is responsible for externally shutdown down
+	  the power of a remote MediaTek SoC MT6323 is connected to through
+	  controlling a tiny circuit BBPU inside MT6323 RTC.
+
+	  Say Y if you have a board where MT6323 could be found.
+
 config POWER_RESET_QNAP
 	bool "QNAP power-off driver"
 	depends on OF_GPIO && PLAT_ORION
diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
index 7778c74..8836172 100644
--- a/drivers/power/reset/Makefile
+++ b/drivers/power/reset/Makefile
@@ -11,6 +11,7 @@ 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_MSM) += msm-poweroff.o
+obj-$(CONFIG_POWER_RESET_MT6323) += mt6323-poweroff.o
 obj-$(CONFIG_POWER_RESET_OCELOT_RESET) += ocelot-reset.o
 obj-$(CONFIG_POWER_RESET_PIIX4_POWEROFF) += piix4-poweroff.o
 obj-$(CONFIG_POWER_RESET_LTC2952) += ltc2952-poweroff.o
diff --git a/drivers/power/reset/mt6323-poweroff.c b/drivers/power/reset/mt6323-poweroff.c
new file mode 100644
index 0000000..c195766
--- /dev/null
+++ b/drivers/power/reset/mt6323-poweroff.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Power off through MediaTek PMIC
+ *
+ * Copyright (C) 2018 MediaTek Inc.
+ *
+ * Author: Sean Wang <sean.wang@xxxxxxxxxxxx>
+ *
+ */
+
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/mt6397/core.h>
+#include <linux/mfd/mt6397/rtc.h>
+
+struct mt6323_pwrc {
+	struct device *dev;
+	struct regmap *regmap;
+	u32 base;
+};
+
+static struct mt6323_pwrc *mt_pwrc;
+
+static void mt6323_do_pwroff(void)
+{
+	struct mt6323_pwrc *pwrc = mt_pwrc;
+	unsigned int val;
+	int ret;
+
+	regmap_write(pwrc->regmap, pwrc->base + RTC_BBPU, RTC_BBPU_KEY);
+	regmap_write(pwrc->regmap, pwrc->base + RTC_WRTGR, 1);
+
+	ret = regmap_read_poll_timeout(pwrc->regmap,
+				       pwrc->base + RTC_BBPU, val,
+				       !(val & RTC_BBPU_CBUSY),
+				       MTK_RTC_POLL_DELAY_US,
+				       MTK_RTC_POLL_TIMEOUT);
+	if (ret)
+		dev_err(pwrc->dev, "failed to write BBPU: %d\n", ret);
+
+	/* Wait some time until system down, otherwise, notice with a warn */
+	mdelay(1000);
+
+	WARN_ONCE(1, "Unable to power off system\n");
+}
+
+static int mt6323_pwrc_probe(struct platform_device *pdev)
+{
+	struct mt6397_chip *mt6397_chip = dev_get_drvdata(pdev->dev.parent);
+	struct mt6323_pwrc *pwrc;
+	struct resource *res;
+
+	pwrc = devm_kzalloc(&pdev->dev, sizeof(*pwrc), GFP_KERNEL);
+	if (!pwrc)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	pwrc->base = res->start;
+	pwrc->regmap = mt6397_chip->regmap;
+	pwrc->dev = &pdev->dev;
+	mt_pwrc = pwrc;
+
+	pm_power_off = &mt6323_do_pwroff;
+
+	return 0;
+}
+
+static int mt6323_pwrc_remove(struct platform_device *pdev)
+{
+	if (pm_power_off == &mt6323_do_pwroff)
+		pm_power_off = NULL;
+
+	return 0;
+}
+
+static const struct of_device_id mt6323_pwrc_dt_match[] = {
+	{ .compatible = "mediatek,mt6323-pwrc" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, mt6323_pwrc_dt_match);
+
+static struct platform_driver mt6323_pwrc_driver = {
+	.probe		= mt6323_pwrc_probe,
+	.remove		= mt6323_pwrc_remove,
+	.driver		= {
+		.name	= "mt6323-pwrc",
+		.of_match_table = mt6323_pwrc_dt_match,
+	},
+};
+
+module_platform_driver(mt6323_pwrc_driver);
+
+MODULE_DESCRIPTION("Poweroff driver for MT6323 PMIC");
+MODULE_AUTHOR("Sean Wang <sean.wang@xxxxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/mfd/mt6397/rtc.h b/include/linux/mfd/mt6397/rtc.h
index 480977c..ac932c9 100644
--- a/include/linux/mfd/mt6397/rtc.h
+++ b/include/linux/mfd/mt6397/rtc.h
@@ -16,6 +16,7 @@
 
 #define RTC_BBPU		0x0000
 #define RTC_BBPU_CBUSY		BIT(6)
+#define RTC_BBPU_KEY            (0x43 << 8)
 
 #define RTC_WRTGR		0x003c
 
-- 
2.7.4