linux-kernel - Re: [PATCH v2 1/2] thermal/drivers/imx_sc: Rely on the platform data to get the resource id

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Message-ID: <92e80c4b-f41f-8822-93f1-2476499d0b6e@linaro.org>
Date:   Thu, 15 Sep 2022 17:53:19 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>
Cc:     rafael@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 1/2] thermal/drivers/imx_sc: Rely on the platform data
 to get the resource id


Shawn, Sascha,

if there is no comment on these two patches. I'll pick them up

Thanks

   -- D.

On 26/08/2022 00:28, Daniel Lezcano wrote:
> On 18/08/2022 10:23, Daniel Lezcano wrote:
>> Currently the imx_sc driver is reimplementing part of the thermal zone
>> parsing from the thermal OF tree code to get the sensor id associated
>> with a thermal zone sensor.
>>
>> The driver platform specific code should know what sensor is present
>> and not rely on the thermal zone description to do a discovery. Well
>> that is arguable but all the other drivers have a per platform data
>> telling what sensor id to use.
>>
>> The imx_sc thermal driver is the only one using a different
>> approach. Not invalid but forcing to keep a specific function
>> 'thermal_zone_of_get_sensor_id()' to get the sensor id for a specific
>> thermal zone as the self-explanatory function tells and having device
>> tree code inside the driver.
>>
>> The thermal OF code had a rework and remains now self-encapsulated
>> with a register/unregister functions and their 'devm' variants, except
>> for the function mentioned above.
>>
>> After investigating, it appears the imx_sc sensor is defined in
>> arch/arm64/boot/dts/freescale/imx8qxp.dtsi:
>>
>> which defines the cpu-thermal zone with the id: IMX_SC_R_SYSTEM
>>
>> This dtsi is included by:
>>   - imx8qxp-ai_ml.dts
>>   - imx8qxp-colibri.dtsi
>>   - imx8qxp-mek.dts
>>
>> The two first ones do not define more thermal zones
>> The third one adds the pmic-thermal0 zone with id: IMX_SC_R_PMIC_0
>>
>> The thermal OF code returns -ENODEV if the thermal zone registration
>> with a specific id fails because the description is not available in
>> the DT for such a sensor id. In this case we continue with the other
>> ids without bailing out with an error.
>>
>> So we can build for the 'fsl,imx-sc-thermal' a compatible data, an
>> array of sensor ids containing IMX_SC_R_SYSTEM and IMX_SC_R_PMIC_0.
>>
>> The latter won't be found but that will not result in an error but a
>> normal case where we continue the initialization with other ids.
>>
>> Just to clarify, it is what the thermal framework does and what the
>> other drivers are expecting: when a registration fails with -ENODEV
>> this is not an error but a case where the description is not found in
>> the device tree, that be can the entire thermal zones description or a
>> specific thermal zone with an unknown id.
>>
>> There is one small functional change but without impact. When there is
>> no 'thermal-zones' description the probe function was returning
>> '-ENODEV', now it returns zero. When a thermal zone fails to register
>> with an error different from '-ENODEV', the error is detected and
>> returned.
>>
>> Change the code accordingly and remove the OF code from the driver.
>>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
>> ---
>> The changes apply on the linux-next branch:
>>
>>   
>> https://git.kernel.org/pub/scm/linux/kernel/git/thermal/linux.git/log/?h=thermal/linux-next 
>>
>>
>> I don't have the platform, so I was not able to test the changes.
>>
>> Changelog:
>>   v2:
>>      - Clarified a bit more the changes description
>>
>>      - Fix use-after-free and add a couple of comments to reflect the
>>       patch description
>>
>>      - Put back the error message in case there is an error with the
>>        registration
>>
> 
> Is there any comment on this change ?
> 
> 
> 


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