[PATCH V4] watchdog: max77620: Add support for watchdog timer

[Laxman Dewangan]

Maxim PMIC MAX77620 is Power management IC which have multiple
sub blocks like regulators (DCDC/LDOs), GPIO, RTC, Clock, Watchdog
timer etc.

Add the driver for watchdog timer under watchdog framework.
The driver implements the watchdog callbacks to start, stop,
ping and set timeout for watchodg framework.

Signed-off-by: Laxman Dewangan <ldewangan@xxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>

---
Changes from V1:
- Remove the error prints from start/stop/ping to simplify the function.
- Instead of stopping running WDT, inform HW RUNNING and update the required
  param accordingly.
- Resequence the param sets for wdt device to avoid race condition, move all
  wdt device setting before registration.

Changes from V2:
- Set timeout regardless of WDT running or not in probe.

Changes from V3:
- Fix typo in comment.
---
 drivers/watchdog/Kconfig        |   9 ++
 drivers/watchdog/Makefile       |   1 +
 drivers/watchdog/max77620_wdt.c | 227 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 237 insertions(+)
 create mode 100644 drivers/watchdog/max77620_wdt.c

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index b54f26c..ca0602d 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -516,6 +516,15 @@ config MAX63XX_WATCHDOG
 	help
 	  Support for memory mapped max63{69,70,71,72,73,74} watchdog timer.
 
+config MAX77620_WATCHDOG
+	tristate "Maxim Max77620 Watchdog Timer"
+	depends on MFD_MAX77620
+	help
+	 This is the driver for the Max77620 watchdog timer.
+	 Say 'Y' here to enable the watchdog timer support for
+	 MAX77620 chips. To compile this driver as a module,
+	 choose M here: the module will be called max77620_wdt.
+
 config IMX2_WDT
 	tristate "IMX2+ Watchdog"
 	depends on ARCH_MXC || ARCH_LAYERSCAPE
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index a46e7c1..5d38173 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -203,6 +203,7 @@ obj-$(CONFIG_TANGOX_WATCHDOG) += tangox_wdt.o
 obj-$(CONFIG_WM831X_WATCHDOG) += wm831x_wdt.o
 obj-$(CONFIG_WM8350_WATCHDOG) += wm8350_wdt.o
 obj-$(CONFIG_MAX63XX_WATCHDOG) += max63xx_wdt.o
+obj-$(CONFIG_MAX77620_WATCHDOG) += max77620_wdt.o
 obj-$(CONFIG_ZIIRAVE_WATCHDOG) += ziirave_wdt.o
 obj-$(CONFIG_SOFT_WATCHDOG) += softdog.o
 obj-$(CONFIG_MENF21BMC_WATCHDOG) += menf21bmc_wdt.o
diff --git a/drivers/watchdog/max77620_wdt.c b/drivers/watchdog/max77620_wdt.c
new file mode 100644
index 0000000..48b84df
--- /dev/null
+++ b/drivers/watchdog/max77620_wdt.c
@@ -0,0 +1,227 @@
+/*
+ * Maxim MAX77620 Watchdog Driver
+ *
+ * Copyright (C) 2016 NVIDIA CORPORATION. All rights reserved.
+ *
+ * Author: Laxman Dewangan <ldewangan@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mfd/max77620.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/watchdog.h>
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+
+struct max77620_wdt {
+	struct device			*dev;
+	struct regmap			*rmap;
+	struct watchdog_device		wdt_dev;
+};
+
+static int max77620_wdt_start(struct watchdog_device *wdt_dev)
+{
+	struct max77620_wdt *wdt = watchdog_get_drvdata(wdt_dev);
+
+	return regmap_update_bits(wdt->rmap, MAX77620_REG_CNFGGLBL2,
+				  MAX77620_WDTEN, MAX77620_WDTEN);
+}
+
+static int max77620_wdt_stop(struct watchdog_device *wdt_dev)
+{
+	struct max77620_wdt *wdt = watchdog_get_drvdata(wdt_dev);
+
+	return regmap_update_bits(wdt->rmap, MAX77620_REG_CNFGGLBL2,
+				  MAX77620_WDTEN, 0);
+}
+
+static int max77620_wdt_ping(struct watchdog_device *wdt_dev)
+{
+	struct max77620_wdt *wdt = watchdog_get_drvdata(wdt_dev);
+
+	return regmap_update_bits(wdt->rmap, MAX77620_REG_CNFGGLBL3,
+				  MAX77620_WDTC_MASK, 0x1);
+}
+
+static int max77620_wdt_set_timeout(struct watchdog_device *wdt_dev,
+				    unsigned int timeout)
+{
+	struct max77620_wdt *wdt = watchdog_get_drvdata(wdt_dev);
+	unsigned int wdt_timeout;
+	u8 regval;
+	int ret;
+
+	switch (timeout) {
+	case 0 ... 2:
+		regval = MAX77620_TWD_2s;
+		wdt_timeout = 2;
+		break;
+
+	case 3 ... 16:
+		regval = MAX77620_TWD_16s;
+		wdt_timeout = 16;
+		break;
+
+	case 17 ... 64:
+		regval = MAX77620_TWD_64s;
+		wdt_timeout = 64;
+		break;
+
+	default:
+		regval = MAX77620_TWD_128s;
+		wdt_timeout = 128;
+		break;
+	}
+
+	ret = regmap_update_bits(wdt->rmap, MAX77620_REG_CNFGGLBL3,
+				 MAX77620_WDTC_MASK, 0x1);
+	if (ret < 0)
+		return ret;
+
+	ret = regmap_update_bits(wdt->rmap, MAX77620_REG_CNFGGLBL2,
+				 MAX77620_TWD_MASK, regval);
+	if (ret < 0)
+		return ret;
+
+	wdt_dev->timeout = wdt_timeout;
+
+	return 0;
+}
+
+static const struct watchdog_info max77620_wdt_info = {
+	.identity = "max77620-watchdog",
+	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
+};
+
+static const struct watchdog_ops max77620_wdt_ops = {
+	.start		= max77620_wdt_start,
+	.stop		= max77620_wdt_stop,
+	.ping		= max77620_wdt_ping,
+	.set_timeout	= max77620_wdt_set_timeout,
+};
+
+static int max77620_wdt_probe(struct platform_device *pdev)
+{
+	struct max77620_wdt *wdt;
+	struct watchdog_device *wdt_dev;
+	unsigned int regval;
+	int ret;
+
+	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
+	if (!wdt)
+		return -ENOMEM;
+
+	wdt->dev = &pdev->dev;
+	wdt->rmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!wdt->rmap) {
+		dev_err(wdt->dev, "Failed to get parent regmap\n");
+		return -ENODEV;
+	}
+
+	wdt_dev = &wdt->wdt_dev;
+	wdt_dev->info = &max77620_wdt_info;
+	wdt_dev->ops = &max77620_wdt_ops;
+	wdt_dev->min_timeout = 2;
+	wdt_dev->max_timeout = 128;
+	wdt_dev->max_hw_heartbeat_ms = 128 * 1000;
+
+	platform_set_drvdata(pdev, wdt);
+
+	/* Enable WD_RST_WK - WDT expire results in a restart */
+	ret = regmap_update_bits(wdt->rmap, MAX77620_REG_ONOFFCNFG2,
+				 MAX77620_ONOFFCNFG2_WD_RST_WK,
+				 MAX77620_ONOFFCNFG2_WD_RST_WK);
+	if (ret < 0) {
+		dev_err(wdt->dev, "Failed to set WD_RST_WK: %d\n", ret);
+		return ret;
+	}
+
+	/* Set WDT clear in OFF and sleep mode */
+	ret = regmap_update_bits(wdt->rmap, MAX77620_REG_CNFGGLBL2,
+				 MAX77620_WDTOFFC | MAX77620_WDTSLPC,
+				 MAX77620_WDTOFFC | MAX77620_WDTSLPC);
+	if (ret < 0) {
+		dev_err(wdt->dev, "Failed to set WDT OFF mode: %d\n", ret);
+		return ret;
+	}
+
+	/* Check if WDT running and if yes then set flags properly */
+	ret = regmap_read(wdt->rmap, MAX77620_REG_CNFGGLBL2, &regval);
+	if (ret < 0) {
+		dev_err(wdt->dev, "Failed to read WDT CFG register: %d\n", ret);
+		return ret;
+	}
+
+	switch (regval & MAX77620_TWD_MASK) {
+	case MAX77620_TWD_2s:
+		wdt_dev->timeout = 2;
+		break;
+	case MAX77620_TWD_16s:
+		wdt_dev->timeout = 16;
+		break;
+	case MAX77620_TWD_64s:
+		wdt_dev->timeout = 64;
+		break;
+	default:
+		wdt_dev->timeout = 128;
+		break;
+	}
+
+	if (regval & MAX77620_WDTEN)
+		set_bit(WDOG_HW_RUNNING, &wdt_dev->status);
+
+	watchdog_set_nowayout(wdt_dev, nowayout);
+	watchdog_set_drvdata(wdt_dev, wdt);
+
+	ret = watchdog_register_device(wdt_dev);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "watchdog registration failed: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int max77620_wdt_remove(struct platform_device *pdev)
+{
+	struct max77620_wdt *wdt = platform_get_drvdata(pdev);
+
+	max77620_wdt_stop(&wdt->wdt_dev);
+	watchdog_unregister_device(&wdt->wdt_dev);
+
+	return 0;
+}
+
+static struct platform_device_id max77620_wdt_devtype[] = {
+	{ .name = "max77620-watchdog", },
+	{ },
+};
+
+static struct platform_driver max77620_wdt_driver = {
+	.driver	= {
+		.name	= "max77620-watchdog",
+	},
+	.probe	= max77620_wdt_probe,
+	.remove	= max77620_wdt_remove,
+	.id_table = max77620_wdt_devtype,
+};
+
+module_platform_driver(max77620_wdt_driver);
+
+MODULE_DESCRIPTION("Max77620 watchdog timer driver");
+
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
+	"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+MODULE_AUTHOR("Laxman Dewangan <ldewangan@xxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
-- 
2.1.4