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Subject: Re: [PATCH v2] thermal: imx: implement runtime PM support
To:     Oleksij Rempel <o.rempel@pengutronix.de>
Cc:     Petr Benes <petrben@gmail.com>,
        =?UTF-8?B?TWljaGFsIFZva8OhxI0=?= <michal.vokac@ysoft.com>,
        linux-pm@vger.kernel.org, Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Amit Kucheria <amitk@kernel.org>, linux-kernel@vger.kernel.org,
        Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        David Jander <david@protonic.nl>,
        Zhang Rui <rui.zhang@intel.com>,
        Fabio Estevam <festevam@gmail.com>,
        linux-arm-kernel@lists.infradead.org
References: <20211019130809.21281-1-o.rempel@pengutronix.de>
 <20211020050459.GE16320@pengutronix.de>
 <CAPwXO5b=z1nhQCo55A_XuK-Es2o7TrL2Vj6AkRSXa3Wxh0s8sA@mail.gmail.com>
 <20211021072000.GC2298@pengutronix.de>
 <afeea08b-6130-3c7c-be03-52691d00be57@linaro.org>
 <20211021074456.GD2298@pengutronix.de>
From:   Daniel Lezcano <daniel.lezcano@linaro.org>
Message-ID: <dace17c6-a31a-9b52-3659-5b36e23f530e@linaro.org>
Date:   Thu, 21 Oct 2021 09:56:15 +0200
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On 21/10/2021 09:44, Oleksij Rempel wrote:
> On Thu, Oct 21, 2021 at 09:41:35AM +0200, Daniel Lezcano wrote:
>> 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?
> 
> I'm OK with both variants. What do you prefer?
> 
> I'll do i on top of PM patch to reduce refactoring overhead, if you OK
> about it.

I prefer you resend a couple of patches but change the subject of this
patch to something like "thermal/drivers/imx: Fix disabled sensor after
handling trip temperature" in order to reflect the problem, not the
solution.

btw: nice fix


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