[v3,5/7] watchdog: Add Nuvoton NCT6694 WDT support

diff --git a/MAINTAINERS b/MAINTAINERS
index eb5d46825e71..496fe7d5a23f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16549,6 +16549,7 @@  F:	drivers/gpio/gpio-nct6694.c
 F:	drivers/i2c/busses/i2c-nct6694.c
 F:	drivers/mfd/nct6694.c
 F:	drivers/net/can/nct6694_canfd.c
+F:	drivers/watchdog/nct6694_wdt.c
 F:	include/linux/mfd/nct6694.h
 
 NVIDIA (rivafb and nvidiafb) FRAMEBUFFER DRIVER
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 2333476a42c0..fbfa5a5f7acf 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -739,6 +739,17 @@  config MAX77620_WATCHDOG
 	  MAX77620 chips. To compile this driver as a module,
 	  choose M here: the module will be called max77620_wdt.
 
+config NCT6694_WATCHDOG
+	tristate "Nuvoton NCT6694 watchdog support"
+	depends on MFD_NCT6694
+	select WATCHDOG_CORE
+	help
+	  Say Y here to support Nuvoton NCT6694 watchdog timer
+	  functionality.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called nct6694_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 386d88d89fe5..8355893b4435 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -232,6 +232,7 @@  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-$(CONFIG_NCT6694_WATCHDOG)	+= nct6694_wdt.o
 obj-$(CONFIG_ZIIRAVE_WATCHDOG) += ziirave_wdt.o
 obj-$(CONFIG_SOFT_WATCHDOG) += softdog.o
 obj-$(CONFIG_MENF21BMC_WATCHDOG) += menf21bmc_wdt.o
diff --git a/drivers/watchdog/nct6694_wdt.c b/drivers/watchdog/nct6694_wdt.c
new file mode 100644
index 000000000000..52b785e2fbd6
--- /dev/null
+++ b/drivers/watchdog/nct6694_wdt.c
@@ -0,0 +1,277 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Nuvoton NCT6694 WDT driver based on USB interface.
+ *
+ * Copyright (C) 2024 Nuvoton Technology Corp.
+ */
+
+#include <linux/kernel.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/nct6694.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/watchdog.h>
+
+#define DRVNAME "nct6694-wdt"
+
+#define NCT6694_DEFAULT_TIMEOUT		10
+#define NCT6694_DEFAULT_PRETIMEOUT	0
+
+/* Host interface */
+#define NCT6694_WDT_MOD			0x07
+
+/* Message Channel*/
+/* Command 00h */
+#define NCT6694_WDT_CMD0_LEN		0x0F
+#define NCT6694_WDT_CMD0_OFFSET(idx)	(idx ? 0x0100 : 0x0000)	/* OFFSET = SEL|CMD */
+
+/* Command 01h */
+#define NCT6694_WDT_CMD1_LEN		0x08
+#define NCT6694_WDT_CMD1_OFFSET(idx)	(idx ? 0x0101 : 0x0001)	/* OFFSET = SEL|CMD */
+
+static unsigned int timeout = NCT6694_DEFAULT_TIMEOUT;
+module_param(timeout, int, 0);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds");
+
+static unsigned int pretimeout = NCT6694_DEFAULT_PRETIMEOUT;
+module_param(pretimeout, int, 0);
+MODULE_PARM_DESC(pretimeout, "Watchdog pre-timeout in seconds");
+
+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) ")");
+
+enum {
+	NCT6694_ACTION_NONE = 0,
+	NCT6694_ACTION_SIRQ,
+	NCT6694_ACTION_GPO,
+};
+
+struct __packed nct6694_wdt_cmd0 {
+	__le32 pretimeout;
+	__le32 timeout;
+	u8 owner;
+	u8 scratch;
+	u8 control;
+	u8 status;
+	__le32 countdown;
+};
+
+struct __packed nct6694_wdt_cmd1 {
+	u32 wdt_cmd;
+	u32 reserved;
+};
+
+struct nct6694_wdt_data {
+	struct watchdog_device wdev;
+	struct device *dev;
+	struct nct6694 *nct6694;
+	struct mutex lock;
+	unsigned char *xmit_buf;
+	unsigned int wdev_idx;
+};
+
+static int nct6694_wdt_setting(struct watchdog_device *wdev,
+			       u32 timeout_val, u8 timeout_act,
+			       u32 pretimeout_val, u8 pretimeout_act)
+{
+	struct nct6694_wdt_data *data = watchdog_get_drvdata(wdev);
+	struct nct6694_wdt_cmd0 *buf = (struct nct6694_wdt_cmd0 *)data->xmit_buf;
+	struct nct6694 *nct6694 = data->nct6694;
+	unsigned int timeout_fmt, pretimeout_fmt;
+
+	guard(mutex)(&data->lock);
+
+	if (pretimeout_val == 0)
+		pretimeout_act = NCT6694_ACTION_NONE;
+
+	timeout_fmt = (timeout_val * 1000) | (timeout_act << 24);
+	pretimeout_fmt = (pretimeout_val * 1000) | (pretimeout_act << 24);
+
+	memset(buf, 0, NCT6694_WDT_CMD0_LEN);
+	buf->timeout = cpu_to_le32(timeout_fmt);
+	buf->pretimeout = cpu_to_le32(pretimeout_fmt);
+
+	return nct6694_write_msg(nct6694, NCT6694_WDT_MOD,
+				 NCT6694_WDT_CMD0_OFFSET(data->wdev_idx),
+				 NCT6694_WDT_CMD0_LEN, buf);
+}
+
+static int nct6694_wdt_start(struct watchdog_device *wdev)
+{
+	struct nct6694_wdt_data *data = watchdog_get_drvdata(wdev);
+	int ret;
+
+	ret = nct6694_wdt_setting(wdev, wdev->timeout, NCT6694_ACTION_GPO,
+				  wdev->pretimeout, NCT6694_ACTION_GPO);
+	if (ret)
+		return ret;
+
+	dev_dbg(data->dev, "Setting WDT(%d): timeout = %d, pretimeout = %d\n",
+		data->wdev_idx, wdev->timeout, wdev->pretimeout);
+
+	return ret;
+}
+
+static int nct6694_wdt_stop(struct watchdog_device *wdev)
+{
+	struct nct6694_wdt_data *data = watchdog_get_drvdata(wdev);
+	struct nct6694_wdt_cmd1 *buf = (struct nct6694_wdt_cmd1 *)data->xmit_buf;
+	struct nct6694 *nct6694 = data->nct6694;
+
+	guard(mutex)(&data->lock);
+
+	memcpy(buf, "WDTC", 4);
+	buf->reserved = 0;
+
+	return nct6694_write_msg(nct6694, NCT6694_WDT_MOD,
+				 NCT6694_WDT_CMD1_OFFSET(data->wdev_idx),
+				 NCT6694_WDT_CMD1_LEN, buf);
+}
+
+static int nct6694_wdt_ping(struct watchdog_device *wdev)
+{
+	struct nct6694_wdt_data *data = watchdog_get_drvdata(wdev);
+	struct nct6694_wdt_cmd1 *buf = (struct nct6694_wdt_cmd1 *)data->xmit_buf;
+	struct nct6694 *nct6694 = data->nct6694;
+
+	guard(mutex)(&data->lock);
+	memcpy(buf, "WDTS", 4);
+	buf->reserved = 0;
+
+	return nct6694_write_msg(nct6694, NCT6694_WDT_MOD,
+				 NCT6694_WDT_CMD1_OFFSET(data->wdev_idx),
+				 NCT6694_WDT_CMD1_LEN, buf);
+}
+
+static int nct6694_wdt_set_timeout(struct watchdog_device *wdev,
+				   unsigned int timeout)
+{
+	int ret;
+
+	ret = nct6694_wdt_setting(wdev, timeout, NCT6694_ACTION_GPO,
+				  wdev->pretimeout, NCT6694_ACTION_GPO);
+	if (ret)
+		return ret;
+
+	wdev->timeout = timeout;
+
+	return 0;
+}
+
+static int nct6694_wdt_set_pretimeout(struct watchdog_device *wdev,
+				      unsigned int pretimeout)
+{
+	int ret;
+
+	ret = nct6694_wdt_setting(wdev, wdev->timeout, NCT6694_ACTION_GPO,
+				  pretimeout, NCT6694_ACTION_GPO);
+	if (ret)
+		return ret;
+
+	wdev->pretimeout = pretimeout;
+
+	return 0;
+}
+
+static unsigned int nct6694_wdt_get_time(struct watchdog_device *wdev)
+{
+	struct nct6694_wdt_data *data = watchdog_get_drvdata(wdev);
+	struct nct6694_wdt_cmd0 *buf = (struct nct6694_wdt_cmd0 *)data->xmit_buf;
+	struct nct6694 *nct6694 = data->nct6694;
+	unsigned int timeleft_ms;
+	int ret;
+
+	guard(mutex)(&data->lock);
+
+	ret = nct6694_read_msg(nct6694, NCT6694_WDT_MOD,
+			       NCT6694_WDT_CMD0_OFFSET(data->wdev_idx),
+			       NCT6694_WDT_CMD0_LEN, buf);
+	if (ret)
+		return 0;
+
+	timeleft_ms = le32_to_cpu(buf->countdown);
+
+	return timeleft_ms / 1000;
+}
+
+static const struct watchdog_info nct6694_wdt_info = {
+	.options = WDIOF_SETTIMEOUT	|
+		   WDIOF_KEEPALIVEPING	|
+		   WDIOF_MAGICCLOSE	|
+		   WDIOF_PRETIMEOUT,
+	.identity = DRVNAME,
+};
+
+static const struct watchdog_ops nct6694_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = nct6694_wdt_start,
+	.stop = nct6694_wdt_stop,
+	.set_timeout = nct6694_wdt_set_timeout,
+	.set_pretimeout = nct6694_wdt_set_pretimeout,
+	.get_timeleft = nct6694_wdt_get_time,
+	.ping = nct6694_wdt_ping,
+};
+
+static int nct6694_wdt_probe(struct platform_device *pdev)
+{
+	const struct mfd_cell *cell = mfd_get_cell(pdev);
+	struct device *dev = &pdev->dev;
+	struct nct6694 *nct6694 = dev_get_drvdata(pdev->dev.parent);
+	struct nct6694_wdt_data *data;
+	struct watchdog_device *wdev;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->xmit_buf = devm_kcalloc(dev, NCT6694_MAX_PACKET_SZ,
+				      sizeof(unsigned char), GFP_KERNEL);
+	if (!data->xmit_buf)
+		return -ENOMEM;
+
+	data->dev = dev;
+	data->nct6694 = nct6694;
+	data->wdev_idx = cell->id;
+
+	wdev = &data->wdev;
+	wdev->info = &nct6694_wdt_info;
+	wdev->ops = &nct6694_wdt_ops;
+	wdev->timeout = timeout;
+	wdev->pretimeout = pretimeout;
+	if (timeout < pretimeout) {
+		dev_warn(data->dev, "pretimeout < timeout. Setting to zero\n");
+		wdev->pretimeout = 0;
+	}
+
+	wdev->min_timeout = 1;
+	wdev->max_timeout = 255;
+
+	mutex_init(&data->lock);
+
+	platform_set_drvdata(pdev, data);
+
+	/* Register watchdog timer device to WDT framework */
+	watchdog_set_drvdata(&data->wdev, data);
+	watchdog_init_timeout(&data->wdev, timeout, dev);
+	watchdog_set_nowayout(&data->wdev, nowayout);
+	watchdog_stop_on_reboot(&data->wdev);
+
+	return devm_watchdog_register_device(dev, &data->wdev);
+}
+
+static struct platform_driver nct6694_wdt_driver = {
+	.driver = {
+		.name	= DRVNAME,
+	},
+	.probe		= nct6694_wdt_probe,
+};
+
+module_platform_driver(nct6694_wdt_driver);
+
+MODULE_DESCRIPTION("USB-WDT driver for NCT6694");
+MODULE_AUTHOR("Ming Yu <tmyu0@nuvoton.com>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:nct6694-wdt");