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From:   Balsam CHIHI <bchihi@baylibre.com>
Date:   Thu, 15 Sep 2022 18:58:13 +0200
Message-ID: <CAGuA+ooEHPiHuGYXOh7s68HRTv9HSr-BexFsCLUPWTMQ3szCfg@mail.gmail.com>
Subject: Re: [PATCH v9,4/7] thermal: mediatek: Add LVTS driver for mt8192
 thermal zones
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.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
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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.

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

Best regards,
Balsam