watchdog: Add MAX6370 watchdog timer driver

MAX6370 watchdog is available e.g. on Freescale P1/P2 RDB-PC boards.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>

drivers/watchdog/Kconfig

@@ -168,6 +168,13 @@ config WDT_GPIO
 	  doc/device-tree-bindings/watchdog/gpio-wdt.txt for
 	  information on how to describe the watchdog in device tree.
 
+config WDT_MAX6370
+	bool "MAX6370 watchdog timer support"
+	depends on WDT
+	select DM_GPIO
+	help
+	  Select this to enable max6370 watchdog timer.
+
 config WDT_MPC8xx
 	bool "MPC8xx watchdog timer support"
 	depends on WDT && MPC8xx

drivers/watchdog/Makefile

@@ -26,6 +26,7 @@ obj-$(CONFIG_WDT_CORTINA) += cortina_wdt.o
 obj-$(CONFIG_WDT_ORION) += orion_wdt.o
 obj-$(CONFIG_WDT_CDNS) += cdns_wdt.o
 obj-$(CONFIG_WDT_GPIO) += gpio_wdt.o
+obj-$(CONFIG_WDT_MAX6370) += max6370_wdt.o
 obj-$(CONFIG_WDT_MPC8xx) += mpc8xx_wdt.o
 obj-$(CONFIG_WDT_MT7620) += mt7620_wdt.o
 obj-$(CONFIG_WDT_MT7621) += mt7621_wdt.o

drivers/watchdog/max6370_wdt.c

@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0+
+// (C) 2022 Pali Rohár <pali@kernel.org>
+
+#include <asm/io.h>
+#include <asm-generic/gpio.h>
+#include <dm.h>
+#include <linux/delay.h>
+#include <wdt.h>
+
+#define MAX6370_SET_MASK	0x7
+#define MAX6370_SET_1MS		0x0
+#define MAX6370_SET_10MS	0x1
+#define MAX6370_SET_30MS	0x2
+#define MAX6370_SET_DISABLE	0x3
+#define MAX6370_SET_100MS	0x4
+#define MAX6370_SET_1S		0x5
+#define MAX6370_SET_10S		0x6
+#define MAX6370_SET_60S		0x7
+
+#define MAX6370_WDI		0x8
+
+struct max6370_wdt {
+	void __iomem *reg;
+	struct gpio_desc gpio_wdi;
+};
+
+static int max6370_wdt_start(struct udevice *dev, u64 ms, ulong flags)
+{
+	struct max6370_wdt *wdt = dev_get_priv(dev);
+	u8 val;
+
+	val = readb(wdt->reg);
+	val &= ~MAX6370_SET_MASK;
+
+	if (ms <= 1)
+		val |= MAX6370_SET_1MS;
+	else if (ms <= 10)
+		val |= MAX6370_SET_10MS;
+	else if (ms <= 30)
+		val |= MAX6370_SET_30MS;
+	else if (ms <= 100)
+		val |= MAX6370_SET_100MS;
+	else if (ms <= 1000)
+		val |= MAX6370_SET_1S;
+	else if (ms <= 10000)
+		val |= MAX6370_SET_10S;
+	else
+		val |= MAX6370_SET_60S;
+
+	writeb(val, wdt->reg);
+
+	return 0;
+}
+
+static int max6370_wdt_stop(struct udevice *dev)
+{
+	struct max6370_wdt *wdt = dev_get_priv(dev);
+	u8 val;
+
+	val = readb(wdt->reg);
+	val &= ~MAX6370_SET_MASK;
+	val |= MAX6370_SET_DISABLE;
+	writeb(val, wdt->reg);
+
+	return 0;
+}
+
+static int max6370_wdt_reset(struct udevice *dev)
+{
+	struct max6370_wdt *wdt = dev_get_priv(dev);
+	u8 val;
+
+	if (dm_gpio_is_valid(&wdt->gpio_wdi)) {
+		dm_gpio_set_value(&wdt->gpio_wdi, 1);
+		udelay(1);
+		dm_gpio_set_value(&wdt->gpio_wdi, 0);
+	} else {
+		val = readb(wdt->reg);
+		writeb(val | MAX6370_WDI, wdt->reg);
+		writeb(val & ~MAX6370_WDI, wdt->reg);
+	}
+
+	return 0;
+}
+
+static int max6370_wdt_probe(struct udevice *dev)
+{
+	struct max6370_wdt *wdt = dev_get_priv(dev);
+
+	wdt->reg = dev_read_addr_ptr(dev);
+	if (!wdt->reg)
+		return -EINVAL;
+
+	/* WDI gpio is optional */
+	gpio_request_by_name(dev, "gpios", 0, &wdt->gpio_wdi, GPIOD_IS_OUT);
+
+	return 0;
+}
+
+static const struct wdt_ops max6370_wdt_ops = {
+	.start = max6370_wdt_start,
+	.stop = max6370_wdt_stop,
+	.reset = max6370_wdt_reset,
+};
+
+static const struct udevice_id max6370_wdt_ids[] = {
+	{ .compatible = "maxim,max6370" },
+	{}
+};
+
+U_BOOT_DRIVER(max6370_wdt) = {
+	.name = "max6370_wdt",
+	.id = UCLASS_WDT,
+	.of_match = max6370_wdt_ids,
+	.probe = max6370_wdt_probe,
+	.priv_auto = sizeof(struct max6370_wdt),
+	.ops = &max6370_wdt_ops,
+};