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SubjectRe: [PATCH v5 1/3] thermal: qcom-spmi: Use PMIC thermal stage 2 for critical trip points
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!

Thanks for the review!

Matthias

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