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Message-ID: <ccd27ec5-6bce-0f5c-1b58-b7bfcbccdeed@collabora.com>
Date:   Fri, 16 Sep 2022 09:33:31 +0200
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Subject: Re: [PATCH v9,4/7] thermal: mediatek: Add LVTS driver for mt8192
 thermal zones
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To:     Balsam CHIHI <bchihi@baylibre.com>
Cc:     rafael@kernel.org, rui.zhang@intel.com, daniel.lezcano@linaro.org,
        amitk@kernel.org, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org, khilman@baylibre.com,
        mka@chromium.org, robh+dt@kernel.org, krzk+dt@kernel.org,
        matthias.bgg@gmail.com, p.zabel@pengutronix.de,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, james.lo@mediatek.com,
        fan.chen@mediatek.com, louis.yu@mediatek.com,
        rex-bc.chen@mediatek.com, abailon@baylibre.com
References: <20220817080757.352021-1-bchihi@baylibre.com>
 <20220817080757.352021-5-bchihi@baylibre.com>
 <8d6383e0-329e-ca91-6e79-85b3806a2af3@collabora.com>
 <CAGuA+ooEHPiHuGYXOh7s68HRTv9HSr-BexFsCLUPWTMQ3szCfg@mail.gmail.com>
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>
In-Reply-To: <CAGuA+ooEHPiHuGYXOh7s68HRTv9HSr-BexFsCLUPWTMQ3szCfg@mail.gmail.com>
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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