linux-kernel - Re: [PATCH v2] thermal: imx: implement runtime PM support

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Date:   Thu, 21 Oct 2021 09:41:35 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Oleksij Rempel <o.rempel@...gutronix.de>,
        Petr Benes <petrben@...il.com>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Amit Kucheria <amitk@...nel.org>,
        Andrzej Pietrasiewicz <andrzej.p@...labora.com>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Zhang Rui <rui.zhang@...el.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, David Jander <david@...tonic.nl>,
        Michal Vokáč <michal.vokac@...ft.com>
Subject: Re: [PATCH v2] thermal: imx: implement runtime PM support

On 21/10/2021 09:20, Oleksij Rempel wrote:
> Hi Petr,
> 
> On Wed, Oct 20, 2021 at 05:53:03PM +0200, Petr Benes wrote:
>> On Wed, 20 Oct 2021 at 07:05, Oleksij Rempel <o.rempel@...gutronix.de> wrote:
>>>
>>> Hi Petr and Michal,
>>>
>>> I forgot to add you for v2 in CC. Please test/review this version.
>>
>> Hi Oleksij,
>>
>> It works good. with PM as well as without PM. The only minor issue I found is,
>> that the first temperature reading (when the driver probes) fails. That is
>> (val & soc_data->temp_valid_mask) == 0) holds true. How does
>> pm_runtime_resume_and_get() behave in imx_thermal_probe()?
>> Does it go through imx_thermal_runtime_resume() with usleep_range()?
> 
> On the first temperature reading, the PM and part of HW is not
> initialized. Current probe sequence is racy and has at least following
> issues:
> - thermal_zone_device_register is executed before HW init was completed.
>   It kind of worked before my patch, becaus part of reinit was done by
>   temperature init. It  worked, since the irq_enabled flag was not set,
>   but potentially would run enable_irq() two times if device is
>   overheated on probe.
> - the imx_thermal core is potentially disable after first race
>   condition:
>   CPU0					CPU1
>   thermal_zone_device_register()
> 					imx_get_temp()
>   					irq_enabled == false
> 						power_up
> 						read_temp
>   power_up
>   						power_down
>   irq_enabled = true;
> 
>   ... at this point imx_thermal is powered down for some amount of time,
>   over temperature IRQ will not be triggered for some amount of time.
> 
> - if some part after thermal_zone_device_register() would fail or
>   deferred, the worker polling temperature will run in to NULL pointer.
>   This issue already happened...
> 
> After migrating to runtime PM, one of issues started to be visible even
> on normal conditions.
> I'll send one more patch with reworking probe sequence.

Are you planning to send a v3 with this patch? Or a separate patch?

[ ... ]


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