Re: [PATCH v2] thermal: tegra-bpmp: Handle offline zones

[Mikko Perttunen]

On 3/30/23 13:03, Daniel Lezcano wrote:
> On 30/03/2023 11:49, Mikko Perttunen wrote:
> > From: Mikko Perttunen <mperttunen@xxxxxxxxxx>
> >
> > Thermal zones located in power domains may not be accessible when
> > the domain is powergated. In this situation, reading the temperature
> > will return -BPMP_EFAULT. When evaluating trips, BPMP will internally
> > use -256C as the temperature for offline zones.
>
> > For smooth operation, for offline zones, return -EAGAIN when reading
> > the temperature and allow registration of zones even if they are
> > offline during probe.
>
> I think it makes more sense to check if the power domain associated with 
> the device is powered up and if not return -EPROBE_DEFER.

The power domains in question are related to computer vision engines 
that only get powered on when in use, possibly never if the user doesn't 
run a computer vision workload on the system. We still want other 
thermal zones to be available.

Mikko

> > Signed-off-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>
> > ---
> > v2:
> > * Adjusted commit message.
> > * Patch 2/2 dropped for now since it is more controversial,
> >    and this patch is more critical.
> >
> >   drivers/thermal/tegra/tegra-bpmp-thermal.c | 9 ++++++++-
> >   1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/thermal/tegra/tegra-bpmp-thermal.c 
> > b/drivers/thermal/tegra/tegra-bpmp-thermal.c
> > index f5fd4018f72f..4ffc3bb3bf35 100644
> > --- a/drivers/thermal/tegra/tegra-bpmp-thermal.c
> > +++ b/drivers/thermal/tegra/tegra-bpmp-thermal.c
> > @@ -52,6 +52,8 @@ static int __tegra_bpmp_thermal_get_temp(struct 
> > tegra_bpmp_thermal_zone *zone,
> >       err = tegra_bpmp_transfer(zone->tegra->bpmp, &msg);
> >       if (err)
> >           return err;
> > +    if (msg.rx.ret == -BPMP_EFAULT)
> > +        return -EAGAIN;
> >       if (msg.rx.ret)
> >           return -EINVAL;
> > @@ -259,7 +261,12 @@ static int tegra_bpmp_thermal_probe(struct 
> > platform_device *pdev)
> >           zone->tegra = tegra;
> >           err = __tegra_bpmp_thermal_get_temp(zone, &temp);
> > -        if (err < 0) {
> > +
> > +        /*
> > +         * Sensors in powergated domains may temporarily fail to be read
> > +         * (-EAGAIN), but will become accessible when the domain is 
> > powered on.
> > +         */
> > +        if (err < 0 && err != -EAGAIN) {
> >               devm_kfree(&pdev->dev, zone);
> >               continue;
> >           }