[v1,5/9] watchdog: Add Nuvoton NCT6694 WDT support

diff --git a/MAINTAINERS b/MAINTAINERS
index eccd5e795daa..63387c0d4ab6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16442,6 +16442,7 @@  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 684b9fe84fff..bc9d63d69204 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
+	If you say yes to this option, support will be included for Nuvoton
+	NCT6694, a USB device to watchdog timer.
+
+	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 ab6f2b41e38e..453ceacd43ab 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -231,6 +231,7 @@  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..68e2926ec504
--- /dev/null
+++ b/drivers/watchdog/nct6694_wdt.c
@@ -0,0 +1,329 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Nuvoton NCT6694 WDT driver based on USB interface.
+ *
+ * Copyright (C) 2024 Nuvoton Technology Corp.
+ */
+
+#include <linux/watchdog.h>
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mfd/core.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/nct6694.h>
+
+#define DRVNAME "nct6694-wdt"
+
+#define WATCHDOG_TIMEOUT	10
+#define WATCHDOG_PRETIMEOUT	0
+
+/* Host interface */
+#define REQUEST_WDT_MOD		0x07
+
+/* Message Channel*/
+/* Command 00h */
+#define REQUEST_WDT_CMD0_LEN	0x0F
+#define REQUEST_WDT_CMD0_OFFSET(idx)	(idx ? 0x0100 : 0x0000)	/* OFFSET = SEL|CMD */
+#define WDT_PRETIMEOUT_IDX	0x00
+#define WDT_PRETIMEOUT_LEN	0x04	/* PRETIMEOUT(3byte) | ACT(1byte) */
+#define WDT_TIMEOUT_IDX		0x04
+#define WDT_TIMEOUT_LEN		0x04	/* TIMEOUT(3byte) | ACT(1byte) */
+#define WDT_COUNTDOWN_IDX	0x0C
+#define WDT_COUNTDOWN_LEN	0x03
+
+#define WDT_PRETIMEOUT_ACT	BIT(1)
+#define WDT_TIMEOUT_ACT		BIT(1)
+
+/* Command 01h */
+#define REQUEST_WDT_CMD1_LEN		0x04
+#define REQUEST_WDT_CMD1_OFFSET(idx)	(idx ? 0x0101 : 0x0001)	/* OFFSET = SEL|CMD */
+#define WDT_CMD_IDX			0x00
+#define WDT_CMD_LEN			0x04
+
+static unsigned int timeout;
+module_param(timeout, int, 0);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds");
+
+static unsigned int 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) ")");
+
+struct nct6694_wdt_data {
+	struct nct6694 *nct6694;
+	struct watchdog_device wdev;
+	unsigned int wdev_idx;
+};
+
+static inline void set_buf32(void *buf, u32 u32_val)
+{
+	u8 *p = (u8 *)buf;
+
+	p[0] = u32_val & 0xFF;
+	p[1] = (u32_val >> 8) & 0xFF;
+	p[2] = (u32_val >> 16) & 0xFF;
+	p[3] = (u32_val >> 24) & 0xFF;
+}
+
+static int nct6694_wdt_start(struct watchdog_device *wdev)
+{
+	struct nct6694_wdt_data *data = watchdog_get_drvdata(wdev);
+
+	pr_debug("%s: WDT(%d) Start\n", __func__, data->wdev_idx);
+
+	return 0;
+}
+
+static int nct6694_wdt_stop(struct watchdog_device *wdev)
+{
+	struct nct6694_wdt_data *data = watchdog_get_drvdata(wdev);
+	struct nct6694 *nct6694 = data->nct6694;
+	unsigned char buf[REQUEST_WDT_CMD1_LEN] = {'W', 'D', 'T', 'C'};
+	int ret;
+
+	pr_debug("%s: WDT(%d) Close\n", __func__, data->wdev_idx);
+	ret = nct6694_write_msg(nct6694, REQUEST_WDT_MOD,
+				REQUEST_WDT_CMD1_OFFSET(data->wdev_idx),
+				REQUEST_WDT_CMD1_LEN, buf);
+	if (ret)
+		pr_err("%s: Failed to start WDT device!\n", __func__);
+
+	return ret;
+}
+
+static int nct6694_wdt_ping(struct watchdog_device *wdev)
+{
+	struct nct6694_wdt_data *data = watchdog_get_drvdata(wdev);
+	struct nct6694 *nct6694 = data->nct6694;
+	unsigned char buf[REQUEST_WDT_CMD1_LEN] = {'W', 'D', 'T', 'S'};
+	int ret;
+
+	pr_debug("%s: WDT(%d) Ping\n", __func__, data->wdev_idx);
+	ret = nct6694_write_msg(nct6694, REQUEST_WDT_MOD,
+				REQUEST_WDT_CMD1_OFFSET(data->wdev_idx),
+				REQUEST_WDT_CMD1_LEN, buf);
+	if (ret)
+		pr_err("%s: Failed to ping WDT device!\n", __func__);
+
+	return ret;
+}
+
+static int nct6694_wdt_set_timeout(struct watchdog_device *wdev,
+				   unsigned int timeout)
+{
+	struct nct6694_wdt_data *data = watchdog_get_drvdata(wdev);
+	struct nct6694 *nct6694 = data->nct6694;
+	unsigned int timeout_fmt, pretimeout_fmt;
+	unsigned char buf[REQUEST_WDT_CMD0_LEN];
+	int ret;
+
+	if (timeout < wdev->pretimeout) {
+		pr_err("%s: 'timeout' must be greater than 'pre timeout'!\n",
+		       __func__);
+		return -EINVAL;
+	}
+
+	timeout_fmt = timeout * 1000 | (WDT_TIMEOUT_ACT << 24);
+	pretimeout_fmt = wdev->pretimeout * 1000 | (WDT_PRETIMEOUT_ACT << 24);
+	set_buf32(&buf[WDT_TIMEOUT_IDX], le32_to_cpu(timeout_fmt));
+	set_buf32(&buf[WDT_PRETIMEOUT_IDX], le32_to_cpu(pretimeout_fmt));
+
+	ret = nct6694_write_msg(nct6694, REQUEST_WDT_MOD,
+				REQUEST_WDT_CMD0_OFFSET(data->wdev_idx),
+				REQUEST_WDT_CMD0_LEN, buf);
+	if (ret) {
+		pr_err("%s: Don't write the setup command in Start stage!\n",
+		       __func__);
+		return ret;
+	}
+
+	wdev->timeout = timeout;
+
+	return 0;
+}
+
+static int nct6694_wdt_set_pretimeout(struct watchdog_device *wdev,
+				      unsigned int pretimeout)
+{
+	struct nct6694_wdt_data *data = watchdog_get_drvdata(wdev);
+	struct nct6694 *nct6694 = data->nct6694;
+	unsigned int timeout_fmt, pretimeout_fmt;
+	unsigned char buf[REQUEST_WDT_CMD0_LEN];
+	int ret;
+
+	if (pretimeout > wdev->timeout) {
+		pr_err("%s: 'pre timeout' must be less than 'timeout'!\n",
+		       __func__);
+		return -EINVAL;
+	}
+	timeout_fmt = wdev->timeout * 1000 | (WDT_TIMEOUT_ACT << 24);
+	pretimeout_fmt = pretimeout * 1000 | (WDT_PRETIMEOUT_ACT << 24);
+	set_buf32(&buf[WDT_TIMEOUT_IDX], le32_to_cpu(timeout_fmt));
+	set_buf32(&buf[WDT_PRETIMEOUT_IDX], le32_to_cpu(pretimeout_fmt));
+
+	ret = nct6694_write_msg(nct6694, REQUEST_WDT_MOD,
+				REQUEST_WDT_CMD0_OFFSET(data->wdev_idx),
+				REQUEST_WDT_CMD0_LEN, buf);
+	if (ret) {
+		pr_err("%s: Don't write the setup command in Start stage!\n", __func__);
+		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 *nct6694 = data->nct6694;
+	unsigned char buf[WDT_COUNTDOWN_LEN];
+	unsigned int timeleft_ms;
+	int ret;
+
+	ret = nct6694_read_msg(nct6694, REQUEST_WDT_MOD,
+			       REQUEST_WDT_CMD0_OFFSET(data->wdev_idx),
+			       REQUEST_WDT_CMD0_LEN, WDT_COUNTDOWN_IDX,
+			       WDT_COUNTDOWN_LEN, buf);
+	if (ret)
+		pr_err("%s: Failed to get WDT device!\n", __func__);
+
+	timeleft_ms = ((buf[2] << 16) | (buf[1] << 8) | buf[0]) & 0xFFFFFF;
+
+	return timeleft_ms / 1000;
+}
+
+static int nct6694_wdt_setup(struct watchdog_device *wdev)
+{
+	struct nct6694_wdt_data *data = watchdog_get_drvdata(wdev);
+	struct nct6694 *nct6694 = data->nct6694;
+	unsigned char buf[REQUEST_WDT_CMD0_LEN] = {0};
+	unsigned int timeout_fmt, pretimeout_fmt;
+	int ret;
+
+	if (timeout)
+		wdev->timeout = timeout;
+
+	if (pretimeout) {
+		wdev->pretimeout = pretimeout;
+		pretimeout_fmt = wdev->pretimeout * 1000 | (WDT_PRETIMEOUT_ACT << 24);
+	} else {
+		pretimeout_fmt = 0;
+	}
+
+	timeout_fmt = wdev->timeout * 1000 | (WDT_TIMEOUT_ACT << 24);
+	set_buf32(&buf[WDT_TIMEOUT_IDX], le32_to_cpu(timeout_fmt));
+	set_buf32(&buf[WDT_PRETIMEOUT_IDX], le32_to_cpu(pretimeout_fmt));
+
+	ret = nct6694_write_msg(nct6694, REQUEST_WDT_MOD,
+				REQUEST_WDT_CMD0_OFFSET(data->wdev_idx),
+				REQUEST_WDT_CMD0_LEN, buf);
+	if (ret)
+		return ret;
+
+	pr_info("Setting WDT(%d): timeout = %d, pretimeout = %d\n",
+		data->wdev_idx, wdev->timeout, wdev->pretimeout);
+
+	return 0;
+}
+
+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 nct6694 *nct6694 = dev_get_drvdata(pdev->dev.parent);
+	struct nct6694_wdt_data *data;
+	struct watchdog_device *wdev;
+	int ret;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->nct6694 = nct6694;
+	data->wdev_idx = cell->id;
+
+	wdev = &data->wdev;
+	wdev->info = &nct6694_wdt_info;
+	wdev->ops = &nct6694_wdt_ops;
+	wdev->timeout = WATCHDOG_TIMEOUT;
+	wdev->pretimeout = WATCHDOG_PRETIMEOUT;
+	wdev->min_timeout = 1;
+	wdev->max_timeout = 255;
+
+	platform_set_drvdata(pdev, data);
+
+	/* Register watchdog timer device to WDT framework */
+	watchdog_set_drvdata(&data->wdev, data);
+	watchdog_init_timeout(&data->wdev, timeout, &pdev->dev);
+	watchdog_set_nowayout(&data->wdev, nowayout);
+	watchdog_stop_on_reboot(&data->wdev);
+
+	ret = devm_watchdog_register_device(&pdev->dev, &data->wdev);
+	if (ret) {
+		dev_err(&pdev->dev, "%s: Failed to register watchdog device: %d\n",
+			__func__, ret);
+		return ret;
+	}
+
+	ret = nct6694_wdt_setup(&data->wdev);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to setup WDT device!\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static struct platform_driver nct6694_wdt_driver = {
+	.driver = {
+		.name	= DRVNAME,
+	},
+	.probe		= nct6694_wdt_probe,
+};
+
+static int __init nct6694_init(void)
+{
+	int err;
+
+	err = platform_driver_register(&nct6694_wdt_driver);
+	if (!err) {
+		if (err)
+			platform_driver_unregister(&nct6694_wdt_driver);
+	}
+
+	return err;
+}
+subsys_initcall(nct6694_init);
+
+static void __exit nct6694_exit(void)
+{
+	platform_driver_unregister(&nct6694_wdt_driver);
+}
+module_exit(nct6694_exit);
+
+MODULE_DESCRIPTION("USB-WDT driver for NCT6694");
+MODULE_AUTHOR("Ming Yu <tmyu0@nuvoton.com>");
+MODULE_LICENSE("GPL");