watchdog: stpmic1: Add STPMIC1 watchdog driver

The STPMIC1 PMIC embeds a watchdog which is disabled by default. As soon
as the watchdog is started, it must be refreshed periodically otherwise
the PMIC goes off.
Signed-off-by: Pascal Paillet <p.paillet@st.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/watchdog/Kconfig

@@ -817,6 +817,18 @@ config STM32_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called stm32_iwdg.
 
+config STPMIC1_WATCHDOG
+	tristate "STPMIC1 PMIC watchdog support"
+	depends on MFD_STPMIC1
+	select WATCHDOG_CORE
+	help
+	  Say Y here to include watchdog support embedded into STPMIC1 PMIC.
+	  If the watchdog timer expires, stpmic1 will shut down all its power
+	  supplies.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called spmic1_wdt.
+
 config UNIPHIER_WATCHDOG
 	tristate "UniPhier watchdog support"
 	depends on ARCH_UNIPHIER || COMPILE_TEST

drivers/watchdog/Makefile

@@ -220,3 +220,4 @@ obj-$(CONFIG_SOFT_WATCHDOG) += softdog.o
 obj-$(CONFIG_MENF21BMC_WATCHDOG) += menf21bmc_wdt.o
 obj-$(CONFIG_MENZ069_WATCHDOG) += menz69_wdt.o
 obj-$(CONFIG_RAVE_SP_WATCHDOG) += rave-sp-wdt.o
+obj-$(CONFIG_STPMIC1_WATCHDOG) += stpmic1_wdt.o

drivers/watchdog/stpmic1_wdt.c

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) STMicroelectronics 2018
+// Author: Pascal Paillet <p.paillet@st.com> for STMicroelectronics.
+
+#include <linux/kernel.h>
+#include <linux/mfd/stpmic1.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/watchdog.h>
+
+/* WATCHDOG CONTROL REGISTER bit */
+#define WDT_START		BIT(0)
+#define WDT_PING		BIT(1)
+#define WDT_START_MASK		BIT(0)
+#define WDT_PING_MASK		BIT(1)
+#define WDT_STOP		0
+
+#define PMIC_WDT_MIN_TIMEOUT 1
+#define PMIC_WDT_MAX_TIMEOUT 256
+#define PMIC_WDT_DEFAULT_TIMEOUT 30
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
+		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+struct stpmic1_wdt {
+	struct stpmic1 *pmic;
+	struct watchdog_device wdtdev;
+};
+
+static int pmic_wdt_start(struct watchdog_device *wdd)
+{
+	struct stpmic1_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	return regmap_update_bits(wdt->pmic->regmap,
+				  WCHDG_CR, WDT_START_MASK, WDT_START);
+}
+
+static int pmic_wdt_stop(struct watchdog_device *wdd)
+{
+	struct stpmic1_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	return regmap_update_bits(wdt->pmic->regmap,
+				  WCHDG_CR, WDT_START_MASK, WDT_STOP);
+}
+
+static int pmic_wdt_ping(struct watchdog_device *wdd)
+{
+	struct stpmic1_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	return regmap_update_bits(wdt->pmic->regmap,
+				  WCHDG_CR, WDT_PING_MASK, WDT_PING);
+}
+
+static int pmic_wdt_set_timeout(struct watchdog_device *wdd,
+				unsigned int timeout)
+{
+	struct stpmic1_wdt *wdt = watchdog_get_drvdata(wdd);
+
+	wdd->timeout = timeout;
+	/* timeout is equal to register value + 1 */
+	return regmap_write(wdt->pmic->regmap, WCHDG_TIMER_CR, timeout - 1);
+}
+
+static const struct watchdog_info pmic_watchdog_info = {
+	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
+	.identity = "STPMIC1 PMIC Watchdog",
+};
+
+static const struct watchdog_ops pmic_watchdog_ops = {
+	.owner = THIS_MODULE,
+	.start = pmic_wdt_start,
+	.stop = pmic_wdt_stop,
+	.ping = pmic_wdt_ping,
+	.set_timeout = pmic_wdt_set_timeout,
+};
+
+static int pmic_wdt_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct stpmic1 *pmic;
+	struct stpmic1_wdt *wdt;
+
+	if (!pdev->dev.parent)
+		return -EINVAL;
+
+	pmic = dev_get_drvdata(pdev->dev.parent);
+	if (!pmic)
+		return -EINVAL;
+
+	wdt = devm_kzalloc(&pdev->dev, sizeof(struct stpmic1_wdt), GFP_KERNEL);
+	if (!wdt)
+		return -ENOMEM;
+
+	wdt->pmic = pmic;
+
+	wdt->wdtdev.info = &pmic_watchdog_info;
+	wdt->wdtdev.ops = &pmic_watchdog_ops;
+	wdt->wdtdev.min_timeout = PMIC_WDT_MIN_TIMEOUT;
+	wdt->wdtdev.max_timeout = PMIC_WDT_MAX_TIMEOUT;
+	wdt->wdtdev.parent = &pdev->dev;
+
+	wdt->wdtdev.timeout = PMIC_WDT_DEFAULT_TIMEOUT;
+	watchdog_init_timeout(&wdt->wdtdev, 0, &pdev->dev);
+
+	watchdog_set_nowayout(&wdt->wdtdev, nowayout);
+	watchdog_set_drvdata(&wdt->wdtdev, wdt);
+
+	ret = devm_watchdog_register_device(&pdev->dev, &wdt->wdtdev);
+	if (ret)
+		return ret;
+
+	dev_dbg(wdt->pmic->dev, "PMIC Watchdog driver probed\n");
+	return 0;
+}
+
+static const struct of_device_id of_pmic_wdt_match[] = {
+	{ .compatible = "st,stpmic1-wdt" },
+	{ },
+};
+
+MODULE_DEVICE_TABLE(of, of_pmic_wdt_match);
+
+static struct platform_driver stpmic1_wdt_driver = {
+	.probe = pmic_wdt_probe,
+	.driver = {
+		.name = "stpmic1-wdt",
+		.of_match_table = of_pmic_wdt_match,
+	},
+};
+module_platform_driver(stpmic1_wdt_driver);
+
+MODULE_DESCRIPTION("Watchdog driver for STPMIC1 device");
+MODULE_AUTHOR("Pascal Paillet <p.paillet@st.com>");
+MODULE_LICENSE("GPL v2");