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SubjectRe: [PATCH v2 3/3] watchdog: sama5d4: Implement resume hook
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On 02/17/2017 07:22 AM, Alexandre Belloni wrote:
> On 17/02/2017 at 06:47:03 -0800, Guenter Roeck wrote:
>> On 02/16/2017 11:30 AM, Alexandre Belloni wrote:
>>> When resuming for the deepest state on sama5d2, it is necessary to restore
>>> MR as the registers are lost.
>>>
>>> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
>>> ---
>>> Changes in v2:
>>> - cache mr beofre suspending
>>>
>>> drivers/watchdog/sama5d4_wdt.c | 32 ++++++++++++++++++++++++++++++++
>>> 1 file changed, 32 insertions(+)
>>>
>>> diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c
>>> index 2a60251806d2..5ddeb4803dc3 100644
>>> --- a/drivers/watchdog/sama5d4_wdt.c
>>> +++ b/drivers/watchdog/sama5d4_wdt.c
>>> @@ -28,6 +28,7 @@
>>> struct sama5d4_wdt {
>>> struct watchdog_device wdd;
>>> void __iomem *reg_base;
>>> + u32 mr;
>>
>> Makes me wonder if we shouldn't just retain the original 'config'
>> (and maybe rename it to 'mr). After all, it _is_ used now.
>>
>>> };
>>>
>>> static int wdt_timeout = WDT_DEFAULT_TIMEOUT;
>>> @@ -248,11 +249,42 @@ static const struct of_device_id sama5d4_wdt_of_match[] = {
>>> };
>>> MODULE_DEVICE_TABLE(of, sama5d4_wdt_of_match);
>>>
>>> +#ifdef CONFIG_PM_SLEEP
>>> +static int sama5d4_wdt_suspend(struct device *dev)
>>> +{
>>> + struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
>>> +
>>> + wdt->mr = wdt_read(wdt, AT91_WDT_MR);
>>> +
>>
>> Wouldn't you want to stop the watchdog here if it is running,
>> ie set AT91_WDT_WDDIS ?
>>
>
> Some existing customers want the watchdog to continue to run while the
> system is suspended.
>
>>> + return 0;
>>> +}
>>> +
>>> +static int sama5d4_wdt_resume(struct device *dev)
>>> +{
>>> + struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
>>> + u32 reg;
>>> +
>>> + reg = wdt_read(wdt, AT91_WDT_MR);
>>> + if (reg & AT91_WDT_WDDIS)
>>> + wdt_write(wdt, AT91_WDT_MR, reg & ~AT91_WDT_WDDIS);
>>> +
>>> + wdt_write(wdt, AT91_WDT_MR, wdt->mr & ~AT91_WDT_WDDIS);
>>
>> Is that necessary ? Why not just write wdt->mr unconditionally ?
>>
>
> Because you can change WDV and WDD *OR* WDDIS but not both at the same
> time.
>

Odd hardware ;-). Please add a comment explaining why the watchdog isn't
stopped on suspend, and why the AT91_WDT_MR has to be reprogrammed on resume.

Thanks,
Guenter

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