Re: [PATCH 1/2] thermal: tegra-bpmp: Handle offline zones

[Mikko Perttunen]

On 2/8/23 12:31, Thierry Reding wrote:
> On Tue, Feb 07, 2023 at 03:56:08PM +0200, 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 and the temperature is considered to be
> > -256C for calculating trips.
>
> Where's that -256C being set? I only see THERMAL_TEMP_INVALID being set
> as the default for a zone, but that's not -274C, not -256C. If that's
> the temperature that you're referring to, it might be better to state
> that we rely on the default temperature rather than any specific number.
>
> Thierry

It is based on BPMP's internal behavior.

Mikko

> > For smooth operation, for offline zones, return -EAGAIN when reading
> > the temperature and allow registration of zones even if they are
> > offline during probe.
> >
> > Signed-off-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>
> > ---
> >   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 c76e1ea62c8a..628b18818ae9 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;
> >   
> > @@ -257,7 +259,12 @@ 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;
> >   		}
> > --
> > 2.39.0