Re: [PATCH 3/3] thermal: core: fix: Check return code of the ->get_max_state() callback

Lukasz Majewski
2014-10-09T16:47:47Z

Hi Zhang,

> On Fri, 2014-10-03 at 12:40 +0200, Lukasz Majewski wrote:
> > Hi Eduardo, Rui,
> >
> > > On Wed, Sep 24, 2014 at 10:27:12AM +0200, Lukasz Majewski wrote:
> > > > Without this check it was possible to execute cooling device
> > > > binding code even when wrong max cooling state was read.
> > > >
> > > > Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
> > >
> > > Acked-by: Eduardo Valentin <edubezval@gmail.com>
> > >
> > > Rui, are you taking these patches? Do you prefer me to collect
> > > them?
> >
> > I'd like to ask you NOT to apply those patches.
> >
> > In short: It will cause regression on all non Exynos boards.
> >
> > Explanation:
> >
> > Up till now the cpu_cooling device was bind even when the
> > get_max_state() returned -EINVAL and everything worked after late
> > cpufreq policy initialization.
> >
> > However, during this time window the thermal driver is not properly
> > configured.
> >
> > Applying PATCH2/3 and PATCH3/3 would cause bind error without any
> > further occasion for re-bind. As a result THERAL will not be present
> > on the target system.
> >
> > It works on the Exynos boards, since at the report_trigger()
> > function, when first trip point is reached, it is checked if
> > cpu_cooling device is bind. If it is not (due to "fixes" at
> > PATCH2/3 and PATCH3/3) it is rebind then.
> >
> > Due to above, I think that it would be best to leave things as they
> > are now and prepare proper fix as suggested by Eduardo.
> >
> Agreed. Can anyone please propose such a patch?

I can propose myself as a volunteer for this. Unfortunately, I won't be
able to provide any code earlier than in two weeks time.

>
> thanks,
> rui
> > >
> > > Cheers
> > >
> > > Eduardo
> > >
> > > > ---
> > > > drivers/thermal/thermal_core.c | 6 ++++--
> > > > 1 file changed, 4 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/thermal/thermal_core.c
> > > > b/drivers/thermal/thermal_core.c index 747618a..8a4dc35 100644
> > > > --- a/drivers/thermal/thermal_core.c
> > > > +++ b/drivers/thermal/thermal_core.c
> > > > @@ -928,7 +928,7 @@ int thermal_zone_bind_cooling_device(struct
> > > > thermal_zone_device *tz, struct thermal_zone_device *pos1;
> > > > struct thermal_cooling_device *pos2;
> > > > unsigned long max_state = 0;
> > > > - int result;
> > > > + int result, ret;
> > > >
> > > > if (trip >= tz->trips || (trip < 0 && trip !=
> > > > THERMAL_TRIPS_NONE)) return -EINVAL;
> > > > @@ -945,7 +945,9 @@ int thermal_zone_bind_cooling_device(struct
> > > > thermal_zone_device *tz, if (tz != pos1 || cdev != pos2)
> > > > return -EINVAL;
> > > >
> > > > - cdev->ops->get_max_state(cdev, &max_state);
> > > > + ret = cdev->ops->get_max_state(cdev, &max_state);
> > > > + if (ret)
> > > > + return ret;
> > > >
> > > > /* lower default 0, upper default max_state */
> > > > lower = lower == THERMAL_NO_LIMIT ? 0 : lower;
> > > > --
> > > > 2.0.0.rc2
> > > >
> >
> >
> >
>

--
Best regards,

Lukasz Majewski

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