Message-ID: <2d21093f-7efd-4356-a1f5-2ae3af4a0da3@roeck-us.net>
Date: Thu, 21 Nov 2024 06:15:12 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Ming Yu <a0282524688@...il.com>, tmyu0@...oton.com, lee@...nel.org,
 linus.walleij@...aro.org, brgl@...ev.pl, andi.shyti@...nel.org,
 mkl@...gutronix.de, mailhol.vincent@...adoo.fr, andrew+netdev@...n.ch,
 davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, wim@...ux-watchdog.org, jdelvare@...e.com,
 alexandre.belloni@...tlin.com
Cc: linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
 linux-i2c@...r.kernel.org, linux-can@...r.kernel.org,
 netdev@...r.kernel.org, linux-watchdog@...r.kernel.org,
 linux-hwmon@...r.kernel.org, linux-rtc@...r.kernel.org
Subject: Re: [PATCH v2 5/7] watchdog: Add Nuvoton NCT6694 WDT support

On 11/20/24 22:40, Ming Yu wrote:
> This driver supports Watchdog timer functionality for NCT6694 MFD
> device based on USB interface.
> 
> Signed-off-by: Ming Yu <tmyu0@...oton.com>
> ---
>   MAINTAINERS                    |   1 +
>   drivers/watchdog/Kconfig       |  11 ++
>   drivers/watchdog/Makefile      |   1 +
>   drivers/watchdog/nct6694_wdt.c | 277 +++++++++++++++++++++++++++++++++
>   4 files changed, 290 insertions(+)
>   create mode 100644 drivers/watchdog/nct6694_wdt.c
> 
> 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..851c1f17712d 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.
> +

It is a peripheral expander, not a "USB device to watchdog timer". Watchdog is only
a small part of its 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..7d2c8d5c6fa3
> --- /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_info(data->dev, "Setting WDT(%d): timeout = %d, pretimeout = %d\n",
> +		 data->wdev_idx, wdev->timeout, wdev->pretimeout);
> +

This is logging noise. Drop or set as debug message.

> +	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)
> +{
> +	struct nct6694_wdt_data *data = watchdog_get_drvdata(wdev);
> +	int ret;
> +
> +	if (timeout < wdev->pretimeout) {
> +		dev_warn(data->dev, "pretimeout < timeout. Setting to zero\n");
> +		wdev->pretimeout = 0;
> +	}
> +
This is only necessary if the pretimeout was not validated during probe
since otherwise the watchdog core does the check. Please validate it there.

> +	ret = nct6694_wdt_setting(wdev, timeout, NCT6694_ACTION_GPO,
> +				  wdev->pretimeout, NCT6694_ACTION_GPO);
> +	if (ret)
> +		return ret;
> +
> +	wdev->timeout = timeout;
> +
> +	return ret;

ret == 0 here, so 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 ret;

ret == 0 here, so 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 ret;

The function does not return an error code. Return 0 instead.
> +
> +	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;

pretimeout should be validated here.

> +	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@...oton.com>");
> +MODULE_LICENSE("GPL");

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