Sender: Guenter Roeck <groeck7@gmail.com>
Date:   Thu, 23 Feb 2023 10:23:41 -0800
From:   Guenter Roeck <linux@roeck-us.net>
To:     Xingyu Wu <xingyu.wu@starfivetech.com>
Cc:     linux-riscv@lists.infradead.org, devicetree@vger.kernel.org,
        linux-watchdog@vger.kernel.org,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Samin Guo <samin.guo@starfivetech.com>,
        linux-kernel@vger.kernel.org, Conor Dooley <conor@kernel.org>
Subject: Re: [PATCH v3 2/2] drivers: watchdog: Add StarFive Watchdog driver
Message-ID: <20230223182341.GA200380@roeck-us.net>
References: <20230220081926.267695-1-xingyu.wu@starfivetech.com>
 <20230220081926.267695-3-xingyu.wu@starfivetech.com>
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In-Reply-To: <20230220081926.267695-3-xingyu.wu@starfivetech.com>
Precedence: bulk

On Mon, Feb 20, 2023 at 04:19:26PM +0800, Xingyu Wu wrote:
> Add watchdog driver for the StarFive JH7110 SoC.
> 
> Signed-off-by: Xingyu Wu <xingyu.wu@starfivetech.com>
> ---
>  MAINTAINERS                     |   7 +
>  drivers/watchdog/Kconfig        |   9 +
>  drivers/watchdog/Makefile       |   2 +
>  drivers/watchdog/starfive-wdt.c | 651 ++++++++++++++++++++++++++++++++
>  4 files changed, 669 insertions(+)
>  create mode 100644 drivers/watchdog/starfive-wdt.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 135d93368d36..6cbcf08fa76a 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -19933,6 +19933,13 @@ F:	Documentation/devicetree/bindings/reset/starfive,jh7100-reset.yaml
>  F:	drivers/reset/reset-starfive-jh7100.c
>  F:	include/dt-bindings/reset/starfive-jh7100.h
>  
> +STARFIVE JH7110 WATCHDOG DRIVER
> +M:	Xingyu Wu <xingyu.wu@starfivetech.com>
> +M:	Samin Guo <samin.guo@starfivetech.com>
> +S:	Supported
> +F:	Documentation/devicetree/bindings/watchdog/starfive*
> +F:	drivers/watchdog/starfive-wdt.c
> +
>  STATIC BRANCH/CALL
>  M:	Peter Zijlstra <peterz@infradead.org>
>  M:	Josh Poimboeuf <jpoimboe@kernel.org>
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 0bc40b763b06..4608eb5c9501 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -2089,6 +2089,15 @@ config UML_WATCHDOG
>  	tristate "UML watchdog"
>  	depends on UML || COMPILE_TEST
>  
> +config STARFIVE_WATCHDOG
> +	tristate "StarFive Watchdog support"
> +	depends on RISCV
> +	select WATCHDOG_CORE
> +	default SOC_STARFIVE
> +	help
> +	  Say Y here to support the watchdog of StarFive JH7110 SoC.
> +	  This driver can also be built as a module if choose M.
> +
>  #
>  # ISA-based Watchdog Cards
>  #
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 9cbf6580f16c..4c0bd377e92a 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -211,6 +211,8 @@ obj-$(CONFIG_WATCHDOG_SUN4V)		+= sun4v_wdt.o
>  # Xen
>  obj-$(CONFIG_XEN_WDT) += xen_wdt.o
>  
> +obj-$(CONFIG_STARFIVE_WATCHDOG) += starfive-wdt.o
> +
>  # Architecture Independent
>  obj-$(CONFIG_BD957XMUF_WATCHDOG) += bd9576_wdt.o
>  obj-$(CONFIG_DA9052_WATCHDOG) += da9052_wdt.o
> diff --git a/drivers/watchdog/starfive-wdt.c b/drivers/watchdog/starfive-wdt.c
> new file mode 100644
> index 000000000000..dfbb80406076
> --- /dev/null
> +++ b/drivers/watchdog/starfive-wdt.c
> @@ -0,0 +1,651 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Starfive Watchdog driver
> + *
> + * Copyright (C) 2022 StarFive Technology Co., Ltd.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/iopoll.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/reset.h>
> +#include <linux/watchdog.h>
> +
> +/* JH7110 WatchDog register define */
> +#define STARFIVE_WDT_JH7110_LOAD	0x000	/* RW: Watchdog load register */
> +#define STARFIVE_WDT_JH7110_VALUE	0x004	/* RO: The current value for the watchdog counter */
> +#define STARFIVE_WDT_JH7110_CONTROL	0x008	/*
> +						 * RW:
> +						 * [0]: reset enable;
> +						 * [1]: int enable/wdt enable/reload counter;
> +						 * [31:2]: reserve.

reserved

> +						 */
> +#define STARFIVE_WDT_JH7110_INTCLR	0x00c	/* WO: clear intterupt && reload the counter */
> +#define STARFIVE_WDT_JH7110_RIS		0x010	/* RO: Raw interrupt status from the counter */
> +#define STARFIVE_WDT_JH7110_IMS		0x014	/* RO: Enabled interrupt status from the counter */
> +#define STARFIVE_WDT_JH7110_LOCK	0xc00	/*
> +						 * RO: Enable write access to all other registers
> +						 * by writing 0x1ACCE551.
> +						 */

"RO" contradicts itself against the rest of the comment. The register is
written to, so it can't bew RO.

> +
> +/* WDOGCONTROL */
> +#define STARFIVE_WDT_ENABLE			0x1
> +#define STARFIVE_WDT_JH7110_EN_SHIFT		0
> +#define STARFIVE_WDT_RESET_EN			0x1
> +#define STARFIVE_WDT_JH7110_RESEN_SHIFT		1
> +
> +/* WDOGLOCK */
> +#define STARFIVE_WDT_LOCKED			BIT(0)
> +#define STARFIVE_WDT_JH7110_UNLOCK_KEY		0x1acce551
> +
> +/* WDOGINTCLR */
> +#define STARFIVE_WDT_INTCLR			0x1
> +
> +#define STARFIVE_WDT_MAXCNT			0xffffffff
> +#define STARFIVE_WDT_DEFAULT_TIME		(15)
> +#define STARFIVE_WDT_DELAY_US			0
> +#define STARFIVE_WDT_TIMEOUT_US			10000
> +
> +/* module parameter */
> +#define STARFIVE_WDT_EARLY_ENA			0
> +
> +static bool nowayout = WATCHDOG_NOWAYOUT;
> +static int heartbeat;
> +static int early_enable = STARFIVE_WDT_EARLY_ENA;
> +
> +module_param(heartbeat, int, 0);
> +module_param(early_enable, int, 0);
> +module_param(nowayout, bool, 0);
> +
> +MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. (default="
> +		 __MODULE_STRING(STARFIVE_WDT_DEFAULT_TIME) ")");
> +MODULE_PARM_DESC(early_enable,
> +		 "Watchdog is started at boot time if set to 1, default="
> +		 __MODULE_STRING(STARFIVE_WDT_EARLY_ENA));
> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
> +		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> +
> +struct starfive_wdt_variant {
> +	u32 control;
> +	u32 load;
> +	u32 enable;
> +	u32 value;
> +	u32 int_clr;
> +	u32 unlock;
> +	u32 unlock_key;
> +	u32 irq_is_raise;
> +	u8 enrst_shift;
> +	u8 en_shift;
> +};
> +
> +struct starfive_wdt {
> +	unsigned long freq;
> +	struct device *dev;
> +	struct watchdog_device wdt_device;
> +	struct clk *core_clk;
> +	struct clk *apb_clk;
> +	struct reset_control *rsts;
> +	const struct starfive_wdt_variant *drv_data;
> +	u32 count;	/*count of timeout*/
> +	u32 reload;	/*restore the count*/
> +	void __iomem *base;
> +	spinlock_t lock;	/* spinlock for register handling */
> +};
> +
> +/* Register bias in JH7110 */
> +static const struct starfive_wdt_variant drv_data_jh7110 = {
> +	.control = STARFIVE_WDT_JH7110_CONTROL,
> +	.load = STARFIVE_WDT_JH7110_LOAD,
> +	.enable = STARFIVE_WDT_JH7110_CONTROL,
> +	.value = STARFIVE_WDT_JH7110_VALUE,
> +	.int_clr = STARFIVE_WDT_JH7110_INTCLR,
> +	.unlock = STARFIVE_WDT_JH7110_LOCK,
> +	.unlock_key = STARFIVE_WDT_JH7110_UNLOCK_KEY,
> +	.irq_is_raise = STARFIVE_WDT_JH7110_IMS,
> +	.enrst_shift = STARFIVE_WDT_JH7110_RESEN_SHIFT,
> +	.en_shift = STARFIVE_WDT_JH7110_EN_SHIFT,
> +};
> +
> +static const struct of_device_id starfive_wdt_match[] = {
> +	{ .compatible = "starfive,jh7110-wdt", .data = &drv_data_jh7110 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, starfive_wdt_match);
> +
> +static const struct platform_device_id starfive_wdt_ids[] = {
> +	{
> +		.name = "starfive-jh7110-wdt",
> +		.driver_data = (unsigned long)&drv_data_jh7110,
> +	},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(platform, starfive_wdt_ids);
> +
> +static int starfive_wdt_get_clock_rate(struct starfive_wdt *wdt)
> +{
> +	wdt->freq = clk_get_rate(wdt->core_clk);
> +	/* The clock rate should not be 0.*/

This is obvious and not worth a comment.

> +	if (wdt->freq)
> +		return 0;
> +
> +	dev_err(wdt->dev, "get clock rate failed.\n");
> +	return -ENOENT;

Error handling should come first

	if (!wdt->freq) {
		dev_err(wdt->dev, "get clock rate failed.\n");
		return -EINVAL;
	}
	return 0;

This is not "No such file or directory" (yes, I see that other drivers
do that, but that doesn't make it better). Use -EINVAL instead.

> +}
> +
> +static int starfive_wdt_get_clock(struct starfive_wdt *wdt)
> +{
> +	wdt->apb_clk = devm_clk_get(wdt->dev, "apb");
> +	if (IS_ERR(wdt->apb_clk)) {
> +		dev_err(wdt->dev, "failed to get apb clock.\n");
> +		return PTR_ERR(wdt->apb_clk);
> +	}
> +
> +	wdt->core_clk = devm_clk_get(wdt->dev, "core");
> +	if (IS_ERR(wdt->core_clk)) {
> +		dev_err(wdt->dev, "failed to get core clock.\n");
> +		return PTR_ERR(wdt->core_clk);
> +	}
> +
> +	return 0;
> +}
> +
> +static int starfive_wdt_reset_init(struct starfive_wdt *wdt)
> +{
> +	int ret = 0;
> +
> +	wdt->rsts = devm_reset_control_array_get_exclusive(wdt->dev);
> +	if (IS_ERR(wdt->rsts)) {
> +		dev_err(wdt->dev, "failed to get rsts error.\n");

I don't think this message is understandable. "failed to get reset
control", maybe. Also, the call may return -EPROBE_DEFER,
which should not generate an error message. Either drop the message
or use dev_err_probe().

> +		ret = PTR_ERR(wdt->rsts);
> +	} else {
> +		ret = reset_control_deassert(wdt->rsts);
> +		if (ret)
> +			dev_err(wdt->dev, "failed to deassert rsts.\n");
> +	}
> +
> +	return ret;
> +}
> +
> +static u32 starfive_wdt_ticks_to_sec(struct starfive_wdt *wdt, u32 ticks)
> +{
> +	return DIV_ROUND_CLOSEST(ticks, wdt->freq);
> +}
> +
> +/*
> + * Write unlock-key to unlock. Write other value to lock. When lock bit is 1,
> + * external accesses to other watchdog registers are ignored.
> + */
> +static bool starfive_wdt_is_locked(struct starfive_wdt *wdt)
> +{
> +	u32 val;
> +
> +	val = readl(wdt->base + wdt->drv_data->unlock);
> +	return !!(val & STARFIVE_WDT_LOCKED);
> +}
> +
> +static void starfive_wdt_unlock(struct starfive_wdt *wdt)
> +{
> +	if (starfive_wdt_is_locked(wdt))
> +		writel(wdt->drv_data->unlock_key,
> +		       wdt->base + wdt->drv_data->unlock);
> +}
> +
> +static void starfive_wdt_lock(struct starfive_wdt *wdt)
> +{
> +	if (!starfive_wdt_is_locked(wdt))
> +		writel(~wdt->drv_data->unlock_key,
> +		       wdt->base + wdt->drv_data->unlock);
> +}
> +
> +/* enable watchdog interrupt to reset/reboot */
> +static void starfive_wdt_enable_reset(struct starfive_wdt *wdt)
> +{
> +	u32 val;
> +
> +	val = readl(wdt->base + wdt->drv_data->control);
> +	val |= STARFIVE_WDT_RESET_EN << wdt->drv_data->enrst_shift;
> +	writel(val, wdt->base + wdt->drv_data->control);
> +}
> +
> +/* disable watchdog interrupt to reset/reboot */
> +static void starfive_wdt_disable_reset(struct starfive_wdt *wdt)
> +{
> +	u32 val;
> +
> +	val = readl(wdt->base + wdt->drv_data->control);
> +	val &= ~(STARFIVE_WDT_RESET_EN << wdt->drv_data->enrst_shift);
> +	writel(val, wdt->base + wdt->drv_data->control);
> +}
> +
> +/* interrupt status whether has been raised from the counter */
> +static bool starfive_wdt_raise_irq_status(struct starfive_wdt *wdt)
> +{
> +	return !!readl(wdt->base + wdt->drv_data->irq_is_raise);
> +}
> +
> +/* clear interrupt signal before initialization or reload */
> +static void starfive_wdt_int_clr(struct starfive_wdt *wdt)
> +{
> +	writel(STARFIVE_WDT_INTCLR, wdt->base + wdt->drv_data->int_clr);
> +}
> +
> +static inline void starfive_wdt_set_count(struct starfive_wdt *wdt, u32 val)
> +{
> +	writel(val, wdt->base + wdt->drv_data->load);
> +}
> +
> +static inline u32 starfive_wdt_get_count(struct starfive_wdt *wdt)
> +{
> +	return readl(wdt->base + wdt->drv_data->value);
> +}
> +
> +/* enable watchdog */
> +static inline void starfive_wdt_enable(struct starfive_wdt *wdt)
> +{
> +	u32 val;
> +
> +	val = readl(wdt->base + wdt->drv_data->enable);
> +	val |= STARFIVE_WDT_ENABLE << wdt->drv_data->en_shift;
> +	writel(val, wdt->base + wdt->drv_data->enable);
> +}
> +
> +/* disable watchdog */
> +static inline void starfive_wdt_disable(struct starfive_wdt *wdt)
> +{
> +	u32 val;
> +
> +	val = readl(wdt->base + wdt->drv_data->enable);
> +	val &= ~(STARFIVE_WDT_ENABLE << wdt->drv_data->en_shift);
> +	writel(val, wdt->base + wdt->drv_data->enable);
> +}
> +
> +static inline void starfive_wdt_set_reload_count(struct starfive_wdt *wdt, u32 count)
> +{
> +	starfive_wdt_set_count(wdt, count);
> +	/* need enable controller to reload counter */
> +	starfive_wdt_enable(wdt);
> +}
> +
> +static unsigned int starfive_wdt_max_timeout(struct starfive_wdt *wdt)
> +{
> +	return DIV_ROUND_UP(STARFIVE_WDT_MAXCNT, (wdt->freq / 2)) - 1;
> +}
> +
> +static unsigned int starfive_wdt_get_timeleft(struct watchdog_device *wdd)
> +{
> +	struct starfive_wdt *wdt = watchdog_get_drvdata(wdd);
> +	u32 count;
> +
> +	starfive_wdt_unlock(wdt);
> +	/*
> +	 * Because set half count value,
> +	 * timeleft value should add the count value before first timeout.
> +	 */
> +	count = starfive_wdt_get_count(wdt);
> +	if (!starfive_wdt_raise_irq_status(wdt))
> +		count += wdt->count;
> +
> +	starfive_wdt_lock(wdt);
> +
> +	return starfive_wdt_ticks_to_sec(wdt, count);
> +}
> +
> +static int starfive_wdt_keepalive(struct watchdog_device *wdd)
> +{
> +	struct starfive_wdt *wdt = watchdog_get_drvdata(wdd);
> +
> +	spin_lock(&wdt->lock);
> +
> +	starfive_wdt_unlock(wdt);
> +	starfive_wdt_int_clr(wdt);
> +	starfive_wdt_set_reload_count(wdt, wdt->count);
> +	starfive_wdt_lock(wdt);
> +
> +	spin_unlock(&wdt->lock);
> +
> +	return 0;
> +}
> +
> +static int starfive_wdt_stop(struct watchdog_device *wdd)
> +{
> +	struct starfive_wdt *wdt = watchdog_get_drvdata(wdd);
> +
> +	spin_lock(&wdt->lock);
> +
> +	starfive_wdt_unlock(wdt);
> +	starfive_wdt_disable_reset(wdt);

Is that necessary ? The watchdog is going to be stopped, after all.

> +	starfive_wdt_int_clr(wdt);
> +	starfive_wdt_disable(wdt);
> +	starfive_wdt_lock(wdt);
> +
> +	spin_unlock(&wdt->lock);
> +
> +	return 0;
> +}
> +
> +static int starfive_wdt_pm_stop(struct watchdog_device *wdd)
> +{
> +	struct starfive_wdt *wdt = watchdog_get_drvdata(wdd);
> +
> +	starfive_wdt_stop(wdd);
> +	pm_runtime_put_sync(wdt->dev);
> +
> +	return 0;
> +}
> +
> +static int starfive_wdt_start(struct watchdog_device *wdd)
> +{
> +	struct starfive_wdt *wdt = watchdog_get_drvdata(wdd);
> +
> +	spin_lock(&wdt->lock);
> +	starfive_wdt_unlock(wdt);
> +	/* disable watchdog, to be safe */
> +	starfive_wdt_disable(wdt);
> +
> +	starfive_wdt_enable_reset(wdt);
> +	starfive_wdt_int_clr(wdt);
> +	starfive_wdt_set_count(wdt, wdt->count);
> +	starfive_wdt_enable(wdt);
> +
> +	starfive_wdt_lock(wdt);
> +	spin_unlock(&wdt->lock);
> +
> +	return 0;
> +}
> +
> +static int starfive_wdt_pm_start(struct watchdog_device *wdd)
> +{
> +	struct starfive_wdt *wdt = watchdog_get_drvdata(wdd);
> +
> +	pm_runtime_get_sync(wdt->dev);
> +
> +	return starfive_wdt_start(wdd);
> +}
> +
> +static int starfive_wdt_set_timeout(struct watchdog_device *wdd,
> +				    unsigned int timeout)
> +{
> +	struct starfive_wdt *wdt = watchdog_get_drvdata(wdd);
> +	unsigned long freq = wdt->freq;
> +
> +	spin_lock(&wdt->lock);
> +
> +	/*
> +	 * This watchdog takes twice timeouts to reset.
> +	 * In order to reduce time to reset, should set half count value.
> +	 */
> +	wdt->count = timeout * freq / 2;
> +	wdd->timeout = timeout;
> +
> +	starfive_wdt_unlock(wdt);
> +	starfive_wdt_disable(wdt);
> +	starfive_wdt_set_reload_count(wdt, wdt->count);
> +	starfive_wdt_enable(wdt);
> +	starfive_wdt_lock(wdt);
> +
> +	spin_unlock(&wdt->lock);
> +
> +	return 0;
> +}
> +
> +#define OPTIONS (WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE)
> +
> +static const struct watchdog_info starfive_wdt_ident = {
> +	.options = OPTIONS,
> +	.identity = "StarFive Watchdog",
> +};
> +
> +static const struct watchdog_ops starfive_wdt_ops = {
> +	.owner = THIS_MODULE,
> +	.start = starfive_wdt_pm_start,
> +	.stop = starfive_wdt_pm_stop,
> +	.ping = starfive_wdt_keepalive,
> +	.set_timeout = starfive_wdt_set_timeout,
> +	.get_timeleft = starfive_wdt_get_timeleft,
> +};
> +
> +static const struct watchdog_device starfive_wdd = {
> +	.info = &starfive_wdt_ident,
> +	.ops = &starfive_wdt_ops,
> +	.timeout = STARFIVE_WDT_DEFAULT_TIME,
> +};
> +
> +static inline const struct starfive_wdt_variant *
> +starfive_wdt_get_drv_data(struct platform_device *pdev)
> +{
> +	const struct starfive_wdt_variant *variant;
> +
> +	variant = of_device_get_match_data(&pdev->dev);
> +	if (!variant) {
> +		/* Device matched by platform_device_id */
> +		variant = (struct starfive_wdt_variant *)
> +			   platform_get_device_id(pdev)->driver_data;
> +	}
> +
> +	return variant;
> +}
> +
> +static int starfive_wdt_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct starfive_wdt *wdt;
> +	int ret;
> +
> +	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
> +	if (!wdt)
> +		return -ENOMEM;
> +
> +	wdt->dev = dev;
> +	spin_lock_init(&wdt->lock);
> +	wdt->wdt_device = starfive_wdd;
> +
> +	wdt->drv_data = starfive_wdt_get_drv_data(pdev);
> +
> +	/* get the memory region for the watchdog timer */
> +	wdt->base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(wdt->base)) {
> +		ret = PTR_ERR(wdt->base);
> +		return ret;
> +	}
> +
> +	platform_set_drvdata(pdev, wdt);
> +	pm_runtime_enable(wdt->dev);
> +
> +	ret = starfive_wdt_get_clock(wdt);
> +	if (ret)
> +		return ret;
> +
> +	if (pm_runtime_enabled(wdt->dev)) {
> +		ret = pm_runtime_get_sync(wdt->dev);
> +		if (ret < 0)
> +			return ret;
> +	} else {
> +		/* runtime PM is disabled but clocks need to be enabled */
> +		ret = clk_prepare_enable(wdt->apb_clk);
> +		if (ret) {
> +			dev_err(wdt->dev, "failed to enable apb_clk.\n");
> +			return ret;
> +		}
> +		ret = clk_prepare_enable(wdt->core_clk);
> +		if (ret) {
> +			dev_err(wdt->dev, "failed to enable core_clk.\n");
> +			goto err_apb_clk_disable;
> +		}
> +	}
> +
> +	ret = starfive_wdt_get_clock_rate(wdt);
> +	if (ret)
> +		goto err_clk_disable;
> +
> +	ret = starfive_wdt_reset_init(wdt);
> +	if (ret)
> +		goto err_clk_disable;
> +
> +	wdt->wdt_device.min_timeout = 1;
> +	wdt->wdt_device.max_timeout = starfive_wdt_max_timeout(wdt);

	wdt->wdt_device.timeout = STARFIVE_WDT_DEFAULT_TIME;

should be set here. Otherwise the warning below would always be seen
if the module parameter is not set.

> +
> +	watchdog_set_drvdata(&wdt->wdt_device, wdt);
> +
> +	/*
> +	 * see if we can actually set the requested heartbeat,
> +	 * and if not, try the default value.
> +	 */
> +	watchdog_init_timeout(&wdt->wdt_device, heartbeat, dev);
> +	if (wdt->wdt_device.timeout == 0 ||

If wdt->wdt_device.timeout is pre-initialized, it will never be 0 here.

> +	    wdt->wdt_device.timeout > wdt->wdt_device.max_timeout) {

That won't happen because watchdog_init_timeout() validates it and does
not update the value if it is out of range.

> +		dev_warn(dev, "heartbeat value out of range, default %d used\n",
> +			 STARFIVE_WDT_DEFAULT_TIME);
> +		wdt->wdt_device.timeout = STARFIVE_WDT_DEFAULT_TIME;

And this is then unnecessary. wdt->wdt_device.timeout will always be
valid if it was pre-initialized.

> +	}
> +	starfive_wdt_set_timeout(&wdt->wdt_device, wdt->wdt_device.timeout);
> +
> +	watchdog_set_nowayout(&wdt->wdt_device, nowayout);
> +	watchdog_stop_on_reboot(&wdt->wdt_device);
> +	watchdog_stop_on_unregister(&wdt->wdt_device);
> +
> +	wdt->wdt_device.parent = dev;
> +
> +	ret = watchdog_register_device(&wdt->wdt_device);
> +	if (ret)
> +		goto err_clk_disable;
> +
> +	if (early_enable) {
> +		starfive_wdt_start(&wdt->wdt_device);
> +		set_bit(WDOG_HW_RUNNING, &wdt->wdt_device.status);

Is it correct to call pm_runtime_put_sync() below if the watchdog
is running ? Doesn't that stop the clock ?

> +	} else {
> +		starfive_wdt_stop(&wdt->wdt_device);
> +	}

Wrong order. This has to be done _before_ the watchdog device is registered
to make sure that the watchdog core knows about WDOG_HW_RUNNING.

> +
> +	pm_runtime_put_sync(wdt->dev);
> +
> +	return 0;
> +
> +err_clk_disable:
> +	clk_disable_unprepare(wdt->core_clk);
> +err_apb_clk_disable:
> +	clk_disable_unprepare(wdt->apb_clk);
> +	pm_runtime_disable(wdt->dev);
> +
> +	return ret;
> +}
> +
> +static int starfive_wdt_remove(struct platform_device *dev)
> +{
> +	struct starfive_wdt *wdt = platform_get_drvdata(dev);
> +
> +	starfive_wdt_stop(&wdt->wdt_device);
> +	watchdog_unregister_device(&wdt->wdt_device);
> +
> +	if (pm_runtime_enabled(wdt->dev)) {
> +		pm_runtime_disable(wdt->dev);
> +	} else {
> +		/* disable clock without PM */
> +		clk_disable_unprepare(wdt->core_clk);
> +		clk_disable_unprepare(wdt->apb_clk);
> +	}
> +
> +	return 0;
> +}
> +
> +static void starfive_wdt_shutdown(struct platform_device *dev)
> +{
> +	struct starfive_wdt *wdt = platform_get_drvdata(dev);
> +
> +	starfive_wdt_pm_stop(&wdt->wdt_device);
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int starfive_wdt_suspend(struct device *dev)
> +{
> +	int ret;
> +	struct starfive_wdt *wdt = dev_get_drvdata(dev);
> +
> +	starfive_wdt_unlock(wdt);
> +
> +	/* Save watchdog state, and turn it off. */
> +	wdt->reload = starfive_wdt_get_count(wdt);
> +
> +	/* Note that WTCNT doesn't need to be saved. */
> +	starfive_wdt_stop(&wdt->wdt_device);
> +	pm_runtime_force_suspend(dev);
> +
> +	starfive_wdt_lock(wdt);
> +
> +	return 0;
> +}
> +
> +static int starfive_wdt_resume(struct device *dev)
> +{
> +	int ret;
> +	struct starfive_wdt *wdt = dev_get_drvdata(dev);
> +
> +	starfive_wdt_unlock(wdt);
> +
> +	pm_runtime_force_resume(dev);
> +
> +	/* Restore watchdog state. */
> +	starfive_wdt_set_reload_count(wdt, wdt->reload);
> +
> +	starfive_wdt_start(&wdt->wdt_device);
> +
> +	starfive_wdt_lock(wdt);
> +
> +	return 0;
> +}
> +#endif /* CONFIG_PM_SLEEP */
> +
> +#ifdef CONFIG_PM
> +static int starfive_wdt_runtime_suspend(struct device *dev)
> +{
> +	struct starfive_wdt *wdt = dev_get_drvdata(dev);
> +
> +	clk_disable_unprepare(wdt->apb_clk);
> +	clk_disable_unprepare(wdt->core_clk);
> +
> +	return 0;
> +}
> +
> +static int starfive_wdt_runtime_resume(struct device *dev)
> +{
> +	struct starfive_wdt *wdt = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = clk_prepare_enable(wdt->apb_clk);
> +	if (ret) {
> +		dev_err(wdt->dev, "failed to enable apb_clk.\n");
> +		return ret;
> +	}
> +
> +	ret = clk_prepare_enable(wdt->core_clk);
> +	if (ret)
> +		dev_err(wdt->dev, "failed to enable core_clk.\n");
> +
> +	return ret;
> +}
> +#endif /* CONFIG_PM */
> +
> +static const struct dev_pm_ops starfive_wdt_pm_ops = {
> +	SET_RUNTIME_PM_OPS(starfive_wdt_runtime_suspend, starfive_wdt_runtime_resume, NULL)
> +	SET_SYSTEM_SLEEP_PM_OPS(starfive_wdt_suspend, starfive_wdt_resume)
> +};
> +
> +static struct platform_driver starfive_wdt_driver = {
> +	.probe		= starfive_wdt_probe,
> +	.remove		= starfive_wdt_remove,
> +	.shutdown	= starfive_wdt_shutdown,
> +	.id_table	= starfive_wdt_ids,
> +	.driver		= {
> +		.name	= "starfive-wdt",
> +		.pm	= &starfive_wdt_pm_ops,
> +		.of_match_table = of_match_ptr(starfive_wdt_match),
> +	},
> +};
> +
> +module_platform_driver(starfive_wdt_driver);
> +
> +MODULE_AUTHOR("Xingyu Wu <xingyu.wu@starfivetech.com>");
> +MODULE_AUTHOR("Samin Guo <samin.guo@starfivetech.com>");
> +MODULE_DESCRIPTION("StarFive Watchdog Device Driver");
> +MODULE_LICENSE("GPL");
> -- 
> 2.25.1
>