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Date:   Tue, 31 Jul 2018 09:21:26 -0700
From:   Matthias Kaehlcke <mka@chromium.org>
To:     Eduardo Valentin <edubezval@gmail.com>
Cc:     Doug Anderson <dianders@chromium.org>,
        Andy Gross <andy.gross@linaro.org>,
        David Brown <david.brown@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Zhang Rui <rui.zhang@intel.com>,
        "open list:ARM/QUALCOMM SUPPORT" <linux-soc@vger.kernel.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>, devicetree@vger.kernel.org,
        linux-pm@vger.kernel.org, David Collins <collinsd@codeaurora.org>,
        Stephen Boyd <sboyd@kernel.org>
Subject: Re: [PATCH v5 1/3] thermal: qcom-spmi: Use PMIC thermal stage 2 for
 critical trip points
Message-ID: <20180731162126.GF68975@google.com>
References: <20180724234636.57137-1-mka@chromium.org>
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On Fri, Jul 27, 2018 at 03:45:06PM -0700, Eduardo Valentin wrote:
> On Fri, Jul 27, 2018 at 03:40:52PM -0700, Eduardo Valentin wrote:
> > On Wed, Jul 25, 2018 at 06:12:28PM -0700, Matthias Kaehlcke wrote:
> > > Hi Doug,
> > > 
> > > On Wed, Jul 25, 2018 at 04:19:56PM -0700, Doug Anderson wrote:
> > > 
> > > > On Tue, Jul 24, 2018 at 4:46 PM, Matthias Kaehlcke <mka@chromium.org> wrote:
> > > > > +static int qpnp_tm_update_critical_trip_temp(struct qpnp_tm_chip *chip,
> > > > > +                                            int temp)
> > > > > +{
> > > > > +       u8 reg;
> > > > > +       bool disable_s2_shutdown = false;
> > > > > +       int ret;
> > > > > +
> > > > > +       WARN_ON(!mutex_is_locked(&chip->lock));
> > > > > +
> > > > > +       /*
> > > > > +        * Default: S2 and S3 shutdown enabled, thresholds at
> > > > > +        * 105C/125C/145C, monitoring at 25Hz
> > > > > +        */
> > > > > +       reg = SHUTDOWN_CTRL1_RATE_25HZ;
> > > > > +
> > > > > +       if ((temp == THERMAL_TEMP_INVALID) ||
> > > > > +           (temp < STAGE2_THRESHOLD_MIN)) {
> > > > > +               chip->thresh = THRESH_MIN;
> > > > > +               goto skip;
> > > > > +       }
> > > > > +
> > > > > +       if (temp <= STAGE2_THRESHOLD_MAX) {
> > > > > +               chip->thresh = THRESH_MAX -
> > > > > +                       ((STAGE2_THRESHOLD_MAX - temp) /
> > > > > +                        TEMP_THRESH_STEP);
> > > > > +               disable_s2_shutdown = true;
> > > > > +       } else {
> > > > > +               chip->thresh = THRESH_MAX;
> > > > > +
> > > > > +               if (!IS_ERR(chip->adc))
> > > > > +                       disable_s2_shutdown = true;
> > > > > +               else
> > > > > +                       dev_warn(chip->dev,
> > > > > +                                "No ADC is configured and critical temperature is above the maximum stage 2 threshold of 140°C! Configuring stage 2 shutdown at 140°C.\n");
> > > > 
> > > > Putting a non-ASCII character (the degree symbol) in your commit
> > > > message is one thing, but are you sure it's wise to put it in the
> > > > kernel logs?
> > > 
> > > A few other drivers also do this
> > > (drivers/gpu/drm/nouveau/nvkm/subdev/clk/base.c,
> > > drivers/macintosh/windfarm_pm121.c), however that doesn't mean it's a
> > > good idea. Will change to degC or C.
> > > 
> > > > > +       }
> > > > > +
> > > > > +skip:
> > > > > +       reg |= chip->thresh;
> > > > > +       if (disable_s2_shutdown)
> > > > > +               reg |= SHUTDOWN_CTRL1_OVERRIDE_S2;
> > > > > +
> > > > > +       ret = qpnp_tm_write(chip, QPNP_TM_REG_SHUTDOWN_CTRL1, reg);
> > > > > +       if (ret < 0)
> > > > > +               return ret;
> > > > > +
> > > > > +       return ret;
> > > > 
> > > > Simplify the above lines to:
> > > > 
> > > > return qpnp_tm_write(chip, QPNP_TM_REG_SHUTDOWN_CTRL1, reg);
> > > 
> > > Ouch, my code is indeed dumb ...
> > > 
> > > > > @@ -313,12 +441,7 @@ static int qpnp_tm_probe(struct platform_device *pdev)
> > > > >         if (ret < 0)
> > > > >                 return ret;
> > > > >
> > > > > -       chip->tz_dev = devm_thermal_zone_of_sensor_register(&pdev->dev, 0, chip,
> > > > > -                                                       &qpnp_tm_sensor_ops);
> > > > > -       if (IS_ERR(chip->tz_dev)) {
> > > > > -               dev_err(&pdev->dev, "failed to register sensor\n");
> > > > > -               return PTR_ERR(chip->tz_dev);
> > > > > -       }
> > > > > +       chip->initialized = true;
> > > > 
> > > > Should we add "thermal_zone_device_update(chip->tz_dev,
> > > > THERMAL_EVENT_UNSPECIFIED);" here
> > > 
> > > Seems reasonable, will do.
> > > 
> > > > ...also: do we care about any type of locking for chip->initialized?
> > > > Technically we can be running on weakly ordered memory so if
> > > > qpnp_tm_update_temp_no_adc() is running on a different processor then
> > > > possibly it could still keep returning the default temperature for a
> > > > little while.  We could try to analyze whether there's some sort of
> > > > implicit barrier or we could add manual memory barriers, but generally
> > > > I try to avoid that and just do the simple locking...  What about just
> > > > setting chip-Initialized = true at the end of qpnp_tm_init() while the
> > > > mutex is still held?
> > > 
> > > Thanks for pointing that out. I agree that we should keep things
> > > simple, chip->initialized to true at the end of qpnp_tm_init() sounds
> > > good to me.
> > > 
> > > > I'd also love to hear from someone with more thermal framework
> > > > experience to make sure it's legit to return a default value if
> > > > someone calls us while we're initting.  It seems sane to me but nice
> > > > to confirm it's OK.
> > > 
> > > An alternative could be to return THERMAL_TEMP_INVALID, however I
> > > don't see this handled outside of thermal_core.c, not sure if it could
> > > throw some other code off.
> > > 
> > > Comments from thermal folks on either approach (or alternatives) are
> > > definitely welcome :)
> > > 
> > > > Overall I like the idea of this patch so hopefully others do too.
> > > > Thanks for sending it out!
> > > 
> > 
> > minor ask for next version
> > 
> > 
> > WARNING: line over 80 characters
> > #159: FILE: drivers/thermal/qcom-spmi-temp-alarm.c:65:
> > +#define STAGE2_THRESHOLD_MIN		125000	/* Stage 2 Threshold
> > Min: 125 C */
> > 
> > WARNING: line over 80 characters
> > #160: FILE: drivers/thermal/qcom-spmi-temp-alarm.c:66:
> > +#define STAGE2_THRESHOLD_MAX		140000	/* Stage 2 Threshold
> > Max: 140 C */
> > 
> > ERROR: trailing statements should be on next line
> > #201: FILE: drivers/thermal/qcom-spmi-temp-alarm.c:186:
> > +	if (!chip->adc)) {
> > 
> > CHECK: Unnecessary parentheses around 'temp == THERMAL_TEMP_INVALID'
> > #227: FILE: drivers/thermal/qcom-spmi-temp-alarm.c:220:
> > +	if ((temp == THERMAL_TEMP_INVALID) ||
> > +	    (temp < STAGE2_THRESHOLD_MIN)) {
> > 
> > CHECK: Unnecessary parentheses around 'temp < STAGE2_THRESHOLD_MIN'
> > #227: FILE: drivers/thermal/qcom-spmi-temp-alarm.c:220:
> > +	if ((temp == THERMAL_TEMP_INVALID) ||
> > +	    (temp < STAGE2_THRESHOLD_MIN)) {
> > 
> > CHECK: Unnecessary parentheses around 'trips[i].type ==
> > THERMAL_TRIP_CRITICAL'
> > #305: FILE: drivers/thermal/qcom-spmi-temp-alarm.c:302:
> > +		if (of_thermal_is_trip_valid(chip->tz_dev, i) &&
> > +		    (trips[i].type == THERMAL_TRIP_CRITICAL))
> > 
> > CHECK: Alignment should match open parenthesis
> > #386: FILE: drivers/thermal/qcom-spmi-temp-alarm.c:427:
> > +	chip->tz_dev = devm_thermal_zone_of_sensor_register(&pdev->dev,
> > 0, chip,
> > +
> > &qpnp_tm_sensor_ops);
> 
> 
> And it would be great if you could combine these two in your a single
> series, say when you fix this patch and send a new version of this
> series, please include these too:
> https://patchwork.kernel.org/patch/10543335/
> https://patchwork.kernel.org/patch/10543333/

Ok, will do