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SubjectRe: [PATCH v3 2/2] watchdog: Add Spreadtrum watchdog driver
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On 10/30/2017 02:18 AM, Baolin Wang wrote:
> 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.
>
Yes, I understand, but that is configurable.

Guenter

>>
>>
>>>>> + 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
>
>
>

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