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

From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Oleksij Rempel <o.rempel@pengutronix.de>, Petr Benes <petrben@gmail.com>
Cc: "Shawn Guo" <shawnguo@kernel.org>,
	"Sascha Hauer" <s.hauer@pengutronix.de>,
	"Amit Kucheria" <amitk@kernel.org>,
	"Andrzej Pietrasiewicz" <andrzej.p@collabora.com>,
	"Fabio Estevam" <festevam@gmail.com>,
	"NXP Linux Team" <linux-imx@nxp.com>,
	"Pengutronix Kernel Team" <kernel@pengutronix.de>,
	"Zhang Rui" <rui.zhang@intel.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	"David Jander" <david@protonic.nl>,
	"Michal Vokáč" <michal.vokac@ysoft.com>
Subject: Re: [PATCH v2] thermal: imx: implement runtime PM support
Date: Thu, 21 Oct 2021 09:41:35 +0200	[thread overview]
Message-ID: <afeea08b-6130-3c7c-be03-52691d00be57@linaro.org> (raw)
In-Reply-To: <20211021072000.GC2298@pengutronix.de>

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@pengutronix.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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