[PATCH 7/8] watchdog: max77714: add driver for the watchdog in the MAX77714 PMIC

[Luca Ceresoli <luca@lucaceresoli.net>]

Add a simple driver to suppor the watchdog embedded in the Maxim MAX77714
PMIC.

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
---
 MAINTAINERS                     |   1 +
 drivers/watchdog/Kconfig        |   9 ++
 drivers/watchdog/Makefile       |   1 +
 drivers/watchdog/max77714_wdt.c | 171 ++++++++++++++++++++++++++++++++
 4 files changed, 182 insertions(+)
 create mode 100644 drivers/watchdog/max77714_wdt.c

diff --git a/MAINTAINERS b/MAINTAINERS
index df394192f14e..08900b5729a5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11390,6 +11390,7 @@ M:	Luca Ceresoli <luca@lucaceresoli.net>
 S:	Maintained
 F:	Documentation/devicetree/bindings/mfd/maxim,max77714.yaml
 F:	drivers/mfd/max77714.c
+F:	drivers/watchdog/max77714_wdt.c
 F:	include/linux/mfd/max77714.h
 
 MAXIM MAX77802 PMIC REGULATOR DEVICE DRIVER
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index bf59faeb3de1..00bc3f932a6c 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -699,6 +699,15 @@ config MAX77620_WATCHDOG
 	 MAX77620 chips. To compile this driver as a module,
 	 choose M here: the module will be called max77620_wdt.
 
+config MAX77714_WATCHDOG
+	tristate "Maxim MAX77714 Watchdog Timer"
+	depends on MFD_MAX77714 || COMPILE_TEST
+	help
+	 This is the driver for watchdog timer in the MAX77714 PMIC.
+	 Say 'Y' here to enable the watchdog timer support for
+	 MAX77714 chips. To compile this driver as a module,
+	 choose M here: the module will be called max77714_wdt.
+
 config IMX2_WDT
 	tristate "IMX2+ Watchdog"
 	depends on ARCH_MXC || ARCH_LAYERSCAPE || COMPILE_TEST
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 1bd2d6f37c53..268a942311a0 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -215,6 +215,7 @@ 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-$(CONFIG_MAX77714_WATCHDOG) += max77714_wdt.o
 obj-$(CONFIG_ZIIRAVE_WATCHDOG) += ziirave_wdt.o
 obj-$(CONFIG_SOFT_WATCHDOG) += softdog.o
 obj-$(CONFIG_MENF21BMC_WATCHDOG) += menf21bmc_wdt.o
diff --git a/drivers/watchdog/max77714_wdt.c b/drivers/watchdog/max77714_wdt.c
new file mode 100644
index 000000000000..2d468db849f9
--- /dev/null
+++ b/drivers/watchdog/max77714_wdt.c
@@ -0,0 +1,171 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Maxim MAX77714 Watchdog Driver
+ *
+ * Copyright (C) 2021 Luca Ceresoli
+ * Author: Luca Ceresoli <luca@lucaceresoli.net>
+ */
+
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/mfd/max77714.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/watchdog.h>
+
+struct max77714_wdt {
+	struct device		*dev;
+	struct regmap		*rmap;
+	struct watchdog_device	wd_dev;
+};
+
+/* Timeout in seconds, indexed by TWD bits of CNFG_GLBL2 register */
+unsigned int max77714_margin_value[] = { 2, 16, 64, 128 };
+
+static int max77714_wdt_start(struct watchdog_device *wd_dev)
+{
+	struct max77714_wdt *wdt = watchdog_get_drvdata(wd_dev);
+
+	return regmap_update_bits(wdt->rmap, MAX77714_CNFG_GLBL2,
+				  MAX77714_WDTEN, MAX77714_WDTEN);
+}
+
+static int max77714_wdt_stop(struct watchdog_device *wd_dev)
+{
+	struct max77714_wdt *wdt = watchdog_get_drvdata(wd_dev);
+
+	return regmap_update_bits(wdt->rmap, MAX77714_CNFG_GLBL2,
+				  MAX77714_WDTEN, 0);
+}
+
+static int max77714_wdt_ping(struct watchdog_device *wd_dev)
+{
+	struct max77714_wdt *wdt = watchdog_get_drvdata(wd_dev);
+
+	return regmap_update_bits(wdt->rmap, MAX77714_CNFG_GLBL3,
+				  MAX77714_WDTC, 1);
+}
+
+static int max77714_wdt_set_timeout(struct watchdog_device *wd_dev,
+				    unsigned int timeout)
+{
+	struct max77714_wdt *wdt = watchdog_get_drvdata(wd_dev);
+	unsigned int new_timeout, new_twd;
+	int err;
+
+	for (new_twd = 0; new_twd < ARRAY_SIZE(max77714_margin_value) - 1; new_twd++)
+		if (timeout <= max77714_margin_value[new_twd])
+			break;
+
+	/* new_wdt is not out of bounds here due to the "- 1" in the for loop */
+	new_timeout = max77714_margin_value[new_twd];
+
+	/*
+	 * "If the value of TWD needs to be changed, clear the system
+	 * watchdog timer first [...], then change the value of TWD."
+	 * (MAX77714 datasheet)
+	 */
+	err = regmap_update_bits(wdt->rmap, MAX77714_CNFG_GLBL3,
+				 MAX77714_WDTC, 1);
+	if (err)
+		return err;
+
+	err = regmap_update_bits(wdt->rmap, MAX77714_CNFG_GLBL2,
+				 MAX77714_TWD_MASK, new_twd);
+	if (err)
+		return err;
+
+	wd_dev->timeout = new_timeout;
+
+	dev_dbg(wdt->dev, "New timeout = %u s (WDT = 0x%x)", new_timeout, new_twd);
+
+	return 0;
+}
+
+static const struct watchdog_info max77714_wdt_info = {
+	.identity = "max77714-watchdog",
+	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
+};
+
+static const struct watchdog_ops max77714_wdt_ops = {
+	.start		= max77714_wdt_start,
+	.stop		= max77714_wdt_stop,
+	.ping		= max77714_wdt_ping,
+	.set_timeout	= max77714_wdt_set_timeout,
+};
+
+static int max77714_wdt_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct max77714_wdt *wdt;
+	struct watchdog_device *wd_dev;
+	unsigned int regval;
+	int err;
+
+	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
+	if (!wdt)
+		return -ENOMEM;
+
+	wdt->dev = dev;
+
+	wd_dev = &wdt->wd_dev;
+	wd_dev->info = &max77714_wdt_info;
+	wd_dev->ops = &max77714_wdt_ops;
+	wd_dev->min_timeout = 2;
+	wd_dev->max_timeout = 128;
+
+	platform_set_drvdata(pdev, wdt);
+	watchdog_set_drvdata(wd_dev, wdt);
+
+	wdt->rmap = dev_get_regmap(dev->parent, NULL);
+	if (!wdt->rmap)
+		return dev_err_probe(wdt->dev, -ENODEV, "Failed to get parent regmap\n");
+
+	/* WD_RST_WK: if 1 wdog restarts; if 0 wdog shuts down */
+	err = regmap_update_bits(wdt->rmap, MAX77714_CNFG2_ONOFF,
+				 MAX77714_WD_RST_WK, MAX77714_WD_RST_WK);
+	if (err)
+		return dev_err_probe(wdt->dev, err, "Error updating CNFG2_ONOFF\n");
+
+	err = regmap_read(wdt->rmap, MAX77714_CNFG_GLBL2, &regval);
+	if (err)
+		return dev_err_probe(wdt->dev, err, "Error reading CNFG_GLBL2\n");
+
+	/* enable watchdog | enable auto-clear in sleep state */
+	regval |= (MAX77714_WDTEN | MAX77714_WDTSLPC);
+
+	err = regmap_write(wdt->rmap, MAX77714_CNFG_GLBL2, regval);
+	if (err)
+		return dev_err_probe(wdt->dev, err, "Error writing CNFG_GLBL2\n");
+
+	wd_dev->timeout = max77714_margin_value[regval & MAX77714_TWD_MASK];
+
+	dev_dbg(wdt->dev, "Timeout = %u s (WDT = 0x%x)",
+		wd_dev->timeout, regval & MAX77714_TWD_MASK);
+
+	set_bit(WDOG_HW_RUNNING, &wd_dev->status);
+
+	watchdog_stop_on_unregister(wd_dev);
+
+	err = devm_watchdog_register_device(dev, wd_dev);
+	if (err)
+		return dev_err_probe(dev, err, "Cannot register watchdog device\n");
+
+	dev_info(dev, "registered as /dev/watchdog%d\n", wd_dev->id);
+
+	return 0;
+}
+
+static struct platform_driver max77714_wdt_driver = {
+	.driver	= {
+		.name	= "max77714-watchdog",
+	},
+	.probe	= max77714_wdt_probe,
+};
+
+module_platform_driver(max77714_wdt_driver);
+
+MODULE_DESCRIPTION("MAX77714 watchdog timer driver");
+MODULE_AUTHOR("Luca Ceresoli <luca@lucaceresoli.net>");
+MODULE_LICENSE("GPL v2");
-- 
2.25.1