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Message-ID: <CAMz4kuLsfZQ-P2Ao43n3OO6_Jbg3uJAjpKxQSdoX8Z9Xo1+xgA@mail.gmail.com>
Date: Mon, 30 Oct 2017 17:18:02 +0800
From: Baolin Wang <baolin.wang@...aro.org>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Wim Van Sebroeck <wim@...ana.be>, Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] watchdog: Add Spreadtrum watchdog driver
Hi Guenter,
(There are some problem with Eric's email, he can not receive this
email, so I help to reply his comments following yours. sorry for
troubles.)
>>>> +#define SPRD_WDT_MAX_TIMEOUT 60
>>>
>>>
>>> Is that really the maximum supported timeout ? Seems a bit low.
>>> Shouldn't it be something like (U32_MAX / SPRD_WDT_CNT_STEP) ?
>>>
>>
>> It supports the max value like as U32_MAX/SPRD_WDT_CNT_STEP,
>> but it doesn't unnecessary to support so big value, if the system can not
>> response it in 60s, the watchdog could trigger timeout.
>>
> It is customary to provide the highest possible value here.
> No one is forced to set such high values. You are making a choice for
> others here. But, sure, if you insist; not worth arguing about.
Eric said 60s is better for us, thanks for your patient explanation.
>
>>>> +
>>>> +#define SPRD_WDT_CNT_HIGH_VALUE 16
>>>
>>>
>>> Maybe name it "SPRD_WDT_CNT_HIGH_SHIFT". It is not really a value,
>>> it is a shift.
>>>
>>
>> Yes, you are right, _SHIFT will be better.
>>
>>>>
>>>> +#define SPRD_WDT_LOW_VALUE_MASK GENMASK(15, 0)
>>>> +#define SPRD_WDT_CNT_VALUE_MAX GENMASK(31, 0)
>>>
>>>
>>> Does this mask serve a useful purpose ?
>>>
>>
>> OK, I will remove it, thanks!
>>
>>>> +#define SPRD_WDT_LOAD_TIMEOUT 1000
>>>> +
>>>> +struct sprd_wdt {
>>>> + void __iomem *base;
>>>> + struct watchdog_device wdd;
>>>> + struct clk *enable;
>>>> + struct clk *rtc_enable;
>>>> + unsigned int irq;
>>>> +};
>>>> +
>>>> +static inline struct sprd_wdt *to_sprd_wdt(struct watchdog_device *wdd)
>>>> +{
>>>> + return container_of(wdd, struct sprd_wdt, wdd);
>>>> +}
>>>> +
>>>> +static inline void sprd_wdt_lock(void __iomem *addr)
>>>> +{
>>>> + writel_relaxed(0x0, addr + SPRD_WDT_LOCK);
>>>> +}
>>>> +
>>>> +static inline void sprd_wdt_unlock(void __iomem *addr)
>>>> +{
>>>> + writel_relaxed(SPRD_WDT_UNLOCK_KEY, addr + SPRD_WDT_LOCK);
>>>> +}
>>>> +
>>>> +static inline bool sprd_wdt_is_running(struct sprd_wdt *wdt)
>>>> +{
>>>> + u32 val;
>>>> +
>>>> + val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>> + return val & SPRD_WDT_NEW_VER_EN;
>>>> +}
>>>> +
>>>> +static irqreturn_t sprd_wdt_isr(int irq, void *dev_id)
>>>> +{
>>>> + struct sprd_wdt *wdt = (struct sprd_wdt *)dev_id;
>>>> +
>>>> + sprd_wdt_unlock(wdt->base);
>>>> + writel_relaxed(SPRD_WDT_INT_CLEAR_BIT, wdt->base +
>>>> SPRD_WDT_INT_CLR);
>>>> + sprd_wdt_lock(wdt->base);
>>>> + watchdog_notify_pretimeout(&wdt->wdd);
>>>> + return IRQ_HANDLED;
>>>> +}
>>>> +
>>>> +static u32 sprd_wdt_get_cnt_value(struct sprd_wdt *wdt)
>>>> +{
>>>> + u32 val;
>>>> +
>>>> + val = readl_relaxed(wdt->base + SPRD_WDT_CNT_HIGH) <<
>>>> + SPRD_WDT_CNT_HIGH_VALUE;
>>>> + val |= readl_relaxed(wdt->base + SPRD_WDT_CNT_LOW) &
>>>> + SPRD_WDT_LOW_VALUE_MASK;
>>>> +
>>>> + return val;
>>>> +}
>>>> +
>>>> +static int sprd_wdt_load_value(struct sprd_wdt *wdt, u32 timeout,
>>>> + u32 pretimeout)
>>>> +{
>>>> + u32 val, delay_cnt = 0;
>>>> + u32 tmr_step = timeout * SPRD_WDT_CNT_STEP;
>>>> + u32 prtmr_step = pretimeout * SPRD_WDT_CNT_STEP;
>>>> +
>>>> + sprd_wdt_unlock(wdt->base);
>>>> + writel_relaxed((tmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
>>>> + SPRD_WDT_LOW_VALUE_MASK, wdt->base +
>>>> SPRD_WDT_LOAD_HIGH);
>>>> + writel_relaxed((tmr_step & SPRD_WDT_LOW_VALUE_MASK),
>>>> + wdt->base + SPRD_WDT_LOAD_LOW);
>>>> + writel_relaxed((prtmr_step >> SPRD_WDT_CNT_HIGH_VALUE) &
>>>> + SPRD_WDT_LOW_VALUE_MASK,
>>>> + wdt->base + SPRD_WDT_IRQ_LOAD_HIGH);
>>>> + writel_relaxed(prtmr_step & SPRD_WDT_LOW_VALUE_MASK,
>>>> + wdt->base + SPRD_WDT_IRQ_LOAD_LOW);
>>>> + sprd_wdt_lock(wdt->base);
>>>> +
>>>> + /*
>>>> + * Waiting the load value operation done,
>>>> + * it needs two or three RTC clock cycles.
>>>> + */
>>>> + do {
>>>> + val = readl_relaxed(wdt->base + SPRD_WDT_INT_RAW);
>>>> + if (!(val & SPRD_WDT_LD_BUSY_BIT))
>>>> + break;
>>>> +
>>>> + cpu_relax();
>>>> + } while (delay_cnt++ < SPRD_WDT_LOAD_TIMEOUT);
>>>> +
>>>> + if (delay_cnt >= SPRD_WDT_LOAD_TIMEOUT)
>>>> + return -EBUSY;
>>>> + return 0;
>>>> +}
>>>> +
>>>> +static int sprd_wdt_enable(struct sprd_wdt *wdt)
>>>> +{
>>>> + u32 val;
>>>> + int ret;
>>>> +
>>>> + ret = clk_prepare_enable(wdt->enable);
>>>> + if (ret)
>>>> + return ret;
>>>> + ret = clk_prepare_enable(wdt->rtc_enable);
>>>> + if (ret)
>>>> + return ret;
>>>> +
>>>> + sprd_wdt_unlock(wdt->base);
>>>> + val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>> + val |= SPRD_WDT_NEW_VER_EN;
>>>> + writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>>> + sprd_wdt_lock(wdt->base);
>>>> + return 0;
>>>> +}
>>>> +
>>>> +static void sprd_wdt_disable(struct sprd_wdt *wdt)
>>>> +{
>>>> + sprd_wdt_unlock(wdt->base);
>>>> + writel_relaxed(0x0, wdt->base + SPRD_WDT_CTRL);
>>>> + sprd_wdt_lock(wdt->base);
>>>> +
>>>> + clk_disable_unprepare(wdt->rtc_enable);
>>>> + clk_disable_unprepare(wdt->enable);
>>>> +}
>>>> +
>>>> +static int sprd_wdt_start(struct watchdog_device *wdd)
>>>> +{
>>>> + struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>> + u32 val;
>>>> + int ret;
>>>> +
>>>> + ret = sprd_wdt_load_value(wdt, wdd->timeout, wdd->pretimeout);
>>>> + if (ret)
>>>> + return ret;
>>>> +
>>>> + sprd_wdt_unlock(wdt->base);
>>>> + val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>> + val |= SPRD_WDT_CNT_EN_BIT | SPRD_WDT_INT_EN_BIT |
>>>> SPRD_WDT_RST_EN_BIT;
>>>> + writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>>> + sprd_wdt_lock(wdt->base);
>>>> + set_bit(WDOG_HW_RUNNING, &wdd->status);
>>>> +
>>>> + return 0;
>>>> +}
>>>> +
>>>> +static int sprd_wdt_stop(struct watchdog_device *wdd)
>>>> +{
>>>> + struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>> + u32 val;
>>>> +
>>>> + sprd_wdt_unlock(wdt->base);
>>>> + val = readl_relaxed(wdt->base + SPRD_WDT_CTRL);
>>>> + val &= ~(SPRD_WDT_CNT_EN_BIT | SPRD_WDT_RST_EN_BIT |
>>>> + SPRD_WDT_INT_EN_BIT);
>>>> + writel_relaxed(val, wdt->base + SPRD_WDT_CTRL);
>>>> + sprd_wdt_lock(wdt->base);
>>>> + return 0;
>>>> +}
>>>> +
>>>> +static int sprd_wdt_set_timeout(struct watchdog_device *wdd,
>>>> + u32 timeout)
>>>> +{
>>>> + struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>> +
>>>> + if (timeout == wdd->timeout)
>>>> + return 0;
>>>> +
>>>> + wdd->timeout = timeout;
>>>> +
>>>> + return sprd_wdt_load_value(wdt, timeout, wdd->pretimeout);
>>>> +}
>>>> +
>>>> +static int sprd_wdt_set_pretimeout(struct watchdog_device *wdd,
>>>> + u32 new_pretimeout)
>>>> +{
>>>> + struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>> +
>>>> + if (new_pretimeout == wdd->pretimeout)
>>>> + return 0;
>>>
>>>
>>> This is inconsistent. pretimeout == 0 is accepted until it is set
>>> to a non-zero value once, then 0 is no longer accepted. pretimeout==0
>>> should reflect "pretimeout disabled". If that is not possible you
>>> need to set some non-0 default value in the probe function.
>>>
>>
>> I understand your opinion, I will fix it.
>>
>>>> + if (new_pretimeout <= wdd->min_timeout)
>>>> + return -EINVAL;
>>>
>>>
>>> Why is pretimeout == wdd->min_timeout invalid ?
>>>
>>
>> OK, you are right, it should be pretimeout < min_timeout.
>>
>>>> +
>>>> + wdd->pretimeout = new_pretimeout;
>>>> +
>>>> + return sprd_wdt_load_value(wdt, wdd->timeout, new_pretimeout);
>>>> +}
>>>> +
>>>> +static u32 sprd_wdt_get_timeleft(struct watchdog_device *wdd)
>>>> +{
>>>> + struct sprd_wdt *wdt = to_sprd_wdt(wdd);
>>>> + u32 val;
>>>> +
>>>> + val = sprd_wdt_get_cnt_value(wdt);
>>>> + val = val / SPRD_WDT_CNT_STEP;
>>>> +
>>>> + return val;
>>>> +}
>>>> +
>>>> +static const struct watchdog_ops sprd_wdt_ops = {
>>>> + .owner = THIS_MODULE,
>>>> + .start = sprd_wdt_start,
>>>> + .stop = sprd_wdt_stop,
>>>> + .set_timeout = sprd_wdt_set_timeout,
>>>> + .set_pretimeout = sprd_wdt_set_pretimeout,
>>>> + .get_timeleft = sprd_wdt_get_timeleft,
>>>
>>>
>>> Just wondering - no heartbeat function ? Having to load the timer
>>> values for each heartbeat is expensive.
>>>
>>
>> Unfortunately, this watchdog has not RELOAD register.
>>
>>>>
>>>> +};
>>>> +
>>>> +static const struct watchdog_info sprd_wdt_info = {
>>>> + .options = WDIOF_SETTIMEOUT |
>>>> + WDIOF_PRETIMEOUT |
>>>> + WDIOF_MAGICCLOSE |
>>>> + WDIOF_KEEPALIVEPING,
>>>> + .identity = "Spreadtrum Watchdog Timer",
>>>> +};
>>>> +
>>>> +static int sprd_wdt_probe(struct platform_device *pdev)
>>>> +{
>>>> + struct resource *wdt_res;
>>>> + struct sprd_wdt *wdt;
>>>> + int ret;
>>>> +
>>>> + wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
>>>> + if (!wdt)
>>>> + return -ENOMEM;
>>>> +
>>>> + wdt_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>>> + if (!wdt_res) {
>>>> + dev_err(&pdev->dev, "failed to memory resource\n");
>>>> + return -ENOMEM;
>>>> + }
>>>
>>>
>>> Unnecessary error check and message. devm_ioremap_resource()
>>> returns an error if res is NULL.
>>>
>>
>> OK, I will fix it.
>>
>>>>
>>>> +
>>>> + wdt->base = devm_ioremap_resource(&pdev->dev, wdt_res);
>>>> + if (IS_ERR(wdt->base))
>>>
>>>
>>> Move the error message to here.
>>>
>>>> + return PTR_ERR(wdt->base);
>>>> +
>>>> + wdt->enable = devm_clk_get(&pdev->dev, "enable");
>>>> + if (IS_ERR(wdt->enable)) {
>>>> + dev_err(&pdev->dev, "can't get the enable clock\n");
>>>> + return PTR_ERR(wdt->enable);
>>>> + }
>>>> +
>>>> + wdt->rtc_enable = devm_clk_get(&pdev->dev, "rtc_enable");
>>>> + if (IS_ERR(wdt->rtc_enable)) {
>>>> + dev_err(&pdev->dev, "can't get the rtc enable clock\n");
>>>> + return PTR_ERR(wdt->rtc_enable);
>>>> + }
>>>> +
>>>> + wdt->irq = platform_get_irq(pdev, 0);
>>>> + if (wdt->irq < 0) {
>>>> + dev_err(&pdev->dev, "failed to get IRQ resource\n");
>>>> + return wdt->irq;
>>>> + }
>>>> +
>>>> + ret = devm_request_irq(&pdev->dev, wdt->irq, sprd_wdt_isr,
>>>> + IRQF_NO_SUSPEND, "sprd-wdt", (void
>>>> *)wdt);
>>>> + if (ret) {
>>>> + dev_err(&pdev->dev, "failed to register irq\n");
>>>> + return ret;
>>>> + }
>>>> +
>>>> + wdt->wdd.info = &sprd_wdt_info;
>>>> + wdt->wdd.ops = &sprd_wdt_ops;
>>>> + wdt->wdd.parent = &pdev->dev;
>>>> + wdt->wdd.min_timeout = SPRD_WDT_MIN_TIMROUT;
>>>> + wdt->wdd.max_timeout = SPRD_WDT_MAX_TIMEOUT;
>>>> +
>>>
>>> You might want to set wdt->wdd.timeout to a default value.
>>>
>>
>> OK, I will set a default timeout value in case of no timeout-sec in
>> device-tree.
>>
>>>>
>>>> + ret = sprd_wdt_enable(wdt);
>>>> + if (ret) {
>>>> + dev_err(&pdev->dev, "failed to enable wdt\n");
>>>> + return ret;
>>>> + }
>>>> +
>>>
>>>
>>> This needs a matching sprd_wdt_disable() call in the remove function.
>>> Best way to handle this would be to add devm_add_action() here.
>>>
>>
>> If add devm_add_action(), it will be called in the remove function,
>> but this is not our expect, if someone remove this module, we want it just
>> timeout.
>>
>
> But that leaves the watchdog enabled even if it was stopped (no call to
> sprd_wdt_disable()).
Eric said It can not be stopped since we have set WATCHDOG_NOWAYOUT,
which means it will reboot the system when removing the watchdog.
> Relying on NOWAYOUT would be a better option here. Again, you are
> making a choice for the user.
we have set WATCHDOG_NOWAYOUT.
>
>
>>>> + watchdog_set_nowayout(&wdt->wdd, WATCHDOG_NOWAYOUT);
>>>> + watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);
>>>> +
>>>> + ret = watchdog_register_device(&wdt->wdd);
>>>
>>>
>>> Unfortunately this doesn't work. It leaves interrupts enabled
>>> after the watchdog device is removed in sprd_wdt_remove(),
>>> but the driver will be gone. I would suggest to use
>>> devm_watchdog_register_device() and reorder calls to request
>>> the interrupt after registering the watchdog device. Then you
>>> can drop the remove function entirely.
>>>
>>
>> Yes, you are right, I understand your opinion, and it is very important,
>> devm_watchdog_register_device() is better. Thanks.
>>
>>>> + if (ret) {
>>>> + sprd_wdt_disable(wdt);
>>>> + dev_err(&pdev->dev, "failed to register watchdog\n");
>>>> + return ret;
>>>> + }
>>>> + platform_set_drvdata(pdev, wdt);
>>>> +
>>>> + return 0;
>>>> +}
>>>> +
>>>> +static int sprd_wdt_remove(struct platform_device *pdev)
>>>> +{
>>>> + struct sprd_wdt *wdt = platform_get_drvdata(pdev);
>>>> +
>>>> + watchdog_unregister_device(&wdt->wdd);
>>>> +
>>>> + if (sprd_wdt_is_running(wdt))
>>>> + dev_crit(&pdev->dev, "Device removed: Expect
>>>> reboot!\n");
>>>> + return 0;
>>>> +}
>>>> +
>>>> +static int __maybe_unused sprd_wdt_pm_suspend(struct device *dev)
>>>> +{
>>>> + struct watchdog_device *wdd = dev_get_drvdata(dev);
>>>> + struct sprd_wdt *wdt = dev_get_drvdata(dev);
>>>> +
>>>> + if (watchdog_active(wdd)) {
>>>> + sprd_wdt_stop(&wdt->wdd);
>>>> + sprd_wdt_disable(wdt);
>>>
>>>
>>> Are you sure you only want to disable the clocks if the watchdog was
>>> active ?
>>> That seems to be a bit inconsistent.
>>>
>>
>> This watchdog is in always on power domain, if system suspend, it needs to
>> disable it, or it will timeout.
>>
> That is not what I asked. I asked why it isn't
>
> if (watchdog_active(wdd))
> sprd_wdt_stop(&wdt->wdd);
>
> sprd_wdt_disable(wdt);
>
> instead.
Yes, Eric will fix this in next version.
>
>>>> + }
>>>> +
>>>> + return 0;
>>>> +}
>>>> +
>>>> +static int __maybe_unused sprd_wdt_pm_resume(struct device *dev)
>>>> +{
>>>> + struct watchdog_device *wdd = dev_get_drvdata(dev);
>>>> + struct sprd_wdt *wdt = dev_get_drvdata(dev);
>>>> + int ret;
>>>> +
>>>> + if (watchdog_active(wdd)) {
>>>> + ret = sprd_wdt_enable(wdt);
>>>> + if (ret)
>>>> + return ret;
>>>> + ret = sprd_wdt_start(&wdt->wdd);
>>>> + if (ret) {
>>>> + sprd_wdt_disable(wdt);
>>>> + return ret;
>>>> + }
>>>
>>>
>>> This can leave the system in an inconsistent state. Sometimes the wdt may
>>> be
>>> disabled, sometimes not.
>>>
>>
>> If watchdog enable failed, it means there is something wrong in this
>> system.
>>
>
>
> True.
>
> Guenter
--
Baolin.wang
Best Regards
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