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Message-ID: <2af40ace-2779-45a0-a244-e7e9e5cc510c@tuxon.dev>
Date: Tue, 23 Jan 2024 09:13:30 +0200
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Subject: Re: [PATCH 07/10] watchdog: rzg2l_wdt: Add suspend/resume support
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To: Guenter Roeck <linux@roeck-us.net>, wim@linux-watchdog.org,
 robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
 geert+renesas@glider.be, magnus.damm@gmail.com, mturquette@baylibre.com,
 sboyd@kernel.org, p.zabel@pengutronix.de, biju.das.jz@bp.renesas.com
Cc: linux-watchdog@vger.kernel.org, devicetree@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
 linux-clk@vger.kernel.org, Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
References: <20240122111115.2861835-1-claudiu.beznea.uj@bp.renesas.com>
 <20240122111115.2861835-8-claudiu.beznea.uj@bp.renesas.com>
 <a5a807c1-76ef-4cf7-a2cf-bc432c420ded@roeck-us.net>
From: claudiu beznea <claudiu.beznea@tuxon.dev>
In-Reply-To: <a5a807c1-76ef-4cf7-a2cf-bc432c420ded@roeck-us.net>
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On 22.01.2024 19:39, Guenter Roeck wrote:
> On 1/22/24 03:11, Claudiu wrote:
>> From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
>>
>> The RZ/G3S supports deep sleep states where power to most of the IP blocks
>> is cut off. To ensure proper working of the watchdog when resuming from
>> such states, the suspend function is stopping the watchdog and the resume
>> function is starting it. There is no need to configure the watchdog
>> in case the watchdog was stopped prior to starting suspend.
>>
>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
>> ---
>>   drivers/watchdog/rzg2l_wdt.c | 26 ++++++++++++++++++++++++++
>>   1 file changed, 26 insertions(+)
>>
>> diff --git a/drivers/watchdog/rzg2l_wdt.c b/drivers/watchdog/rzg2l_wdt.c
>> index 9333dc1a75ab..186796b739f7 100644
>> --- a/drivers/watchdog/rzg2l_wdt.c
>> +++ b/drivers/watchdog/rzg2l_wdt.c
>> @@ -279,6 +279,7 @@ static int rzg2l_wdt_probe(struct platform_device *pdev)
>>       priv->wdev.timeout = WDT_DEFAULT_TIMEOUT;
>>         watchdog_set_drvdata(&priv->wdev, priv);
>> +    dev_set_drvdata(dev, priv);
>>       ret = devm_add_action_or_reset(&pdev->dev, rzg2l_wdt_pm_disable,
>> &priv->wdev);
>>       if (ret)
>>           return ret;
>> @@ -300,10 +301,35 @@ static const struct of_device_id rzg2l_wdt_ids[] = {
>>   };
>>   MODULE_DEVICE_TABLE(of, rzg2l_wdt_ids);
>>   +static int rzg2l_wdt_suspend_late(struct device *dev)
>> +{
>> +    struct rzg2l_wdt_priv *priv = dev_get_drvdata(dev);
>> +
>> +    if (!watchdog_active(&priv->wdev))
>> +        return 0;
>> +
>> +    return rzg2l_wdt_stop(&priv->wdev);
>> +}
>> +
>> +static int rzg2l_wdt_resume_early(struct device *dev)
>> +{
>> +    struct rzg2l_wdt_priv *priv = dev_get_drvdata(dev);
>> +
>> +    if (!watchdog_active(&priv->wdev))
>> +        return 0;
>> +
>> +    return rzg2l_wdt_start(&priv->wdev);
>> +}
>> +
>> +static const struct dev_pm_ops rzg2l_wdt_pm_ops = {
>> +    LATE_SYSTEM_SLEEP_PM_OPS(rzg2l_wdt_suspend_late,
>> rzg2l_wdt_resume_early)
>> +};
>> +
>>   static struct platform_driver rzg2l_wdt_driver = {
>>       .driver = {
>>           .name = "rzg2l_wdt",
>>           .of_match_table = rzg2l_wdt_ids,
>> +        .pm = pm_ptr(&rzg2l_wdt_pm_ops),
> 
> I think this will create a build error if CONFIG_PM=n because rzg2l_wdt_pm_ops
> will be unused but is not marked with __maybe_unused.

The necessity of __maybe_unused has been removed along with the
introduction of LATE_SYSTEM_SLEEP_PM_OPS() and friends (and
*SET_*LATE_SYSTEM_SLEEP_PM_OPS along with the other helpers were marked
deprecated for that) and we can use pm_ptr() along with
LATE_SYSTEM_SLEEP_PM_OPS() to avoid build errors you mentioned.

FYI, I just build the driver with CONFIG_PM=n and all good.

> But then the driver
> won't be
> operational with CONFIG_PM=n, so I really wonder if it makes sense to
> include any
> such conditional code instead of making the driver depend on CONFIG_PM.

That's true. The driver wouldn't work if the CONFIG_PM=n but then it
depends on COMPILE_TEST which is exactly for this (just to compile test it
for platforms that don't support it). I see many watchdog drivers depends
on COMPILE_TEST.

Give this, please let me know would you like me to proceed with it.

Thank you,
Claudiu Beznea

> 
> I really don't think it is desirable to suggest that the driver would work
> with
> CONFIG_PM=n if that isn't really true.
> 
> Guenter
> 
>>       },
>>       .probe = rzg2l_wdt_probe,
>>   };
>