linux-kernel - Re: [PATCH v9,4/7] thermal: mediatek: Add LVTS driver for mt8192 thermal zones

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Date:   Fri, 16 Sep 2022 09:33:31 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Balsam CHIHI <bchihi@...libre.com>
Cc:     rafael@...nel.org, rui.zhang@...el.com, daniel.lezcano@...aro.org,
        amitk@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, khilman@...libre.com,
        mka@...omium.org, robh+dt@...nel.org, krzk+dt@...nel.org,
        matthias.bgg@...il.com, p.zabel@...gutronix.de,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, james.lo@...iatek.com,
        fan.chen@...iatek.com, louis.yu@...iatek.com,
        rex-bc.chen@...iatek.com, abailon@...libre.com
Subject: Re: [PATCH v9,4/7] thermal: mediatek: Add LVTS driver for mt8192
 thermal zones

Il 15/09/22 18:58, Balsam CHIHI ha scritto:
> Hi Angelo,
> 
>>> +static int soc_temp_lvts_read_temp(void *data, int *temperature)
>>> +{
>>> +     struct soc_temp_tz *lvts_tz = (struct soc_temp_tz *)data;
>>> +     struct lvts_data *lvts_data = lvts_tz->lvts_data;
>>> +     struct device *dev = lvts_data->dev;
>>> +     unsigned int msr_raw;
>>> +
>>> +     msr_raw = readl(lvts_data->reg[lvts_tz->id]) & MRS_RAW_MASK;
>>> +     if (msr_raw == 0) {
>>> +             /* Prevents a false critical temperature trap */
>>> +             *temperature = 0;
>>> +             dev_dbg(dev, "LVTS not yet ready\n");
>>
>> ...and you're not returning an error code, despite this function was called
>> while LVTS is still not ready? :-)
>>
> 
> if I add "return -ENAVAIL;" here, I will get the following errors on boot :
> [    0.292094] thermal thermal_zone0: failed to read out thermal zone (-119)
> [    0.293019] thermal thermal_zone1: failed to read out thermal zone (-119)
> [    0.294158] thermal thermal_zone6: failed to read out thermal zone (-119)
> [    0.295697] thermal thermal_zone9: failed to read out thermal zone (-119)
> [    0.296600] thermal thermal_zone10: failed to read out thermal zone (-119)
> [    0.297698] thermal thermal_zone15: failed to read out thermal zone (-119)
> [    0.298625] thermal thermal_zone16: failed to read out thermal zone (-119)
> 
> I just preferred : *temperature = 0; to avoid a false critical temperature trap,
> and "return 0;" to suppress these errors.
> After that (first read at boot when LVTS is not fully ready),
> "msr_raw" will be always != 0.
> And I did not want to add a "delay" or a "sleep".
> Please let me know if you have any suggestions that could fix it in a
> better way.
> 

It's the wrong error number. You have to return -EAGAIN :-)

>>> +
>>> +     } else
>>> +             *temperature = lvts_raw_to_temp(&lvts_data->coeff, msr_raw);
>>> +
>>> +     return 0;
>>> +}
> 
> Best regards,
> Balsam