[Nouveau] [PATCH] drm/nouveau: Don't disable polling in fallback mode

[Ilia Mirkin]

Ben - ping? Just ran into this myself on a NV42.

On Wed, Nov 14, 2018 at 11:01 AM Takashi Iwai <tiwai at suse.de> wrote:
>
> On Fri, 14 Sep 2018 13:59:25 +0200,
> Martin Peres wrote:
> >
> > On 14/09/2018 10:28, Ben Skeggs wrote:
> > > On Wed, 12 Sep 2018 at 20:59, Takashi Iwai <tiwai at suse.de> wrote:
> > >>
> > >> When a fan is controlled via linear fallback without cstate, we
> > >> shouldn't stop polling.  Otherwise it won't be adjusted again and
> > >> keeps running at an initial crazy pace.
> > > Martin,
> > >
> > > Any thoughts on this?
> > >
> > > Ben.
> >
> > Wow, blast from the past!
> >
> > Anyway, the analysis is pretty spot on here. When using the cstate-based
> > fan speed (change the speed of the fan based on what frequency is used),
> > then polling is unnecessary and this function should only be called when
> > changing the pstate.
> >
> > However, in the absence of ANY information, we fallback to a
> > temperature-based management which requires constant polling, so the
> > patch is accurate and poll = false should only be set if we have a cstate.
> >
> > So, the patch is Reviewed-by: Martin Peres <martin.peres at free.fr>
>
> Just a gentle reminder: this patch seems forgotten for 4.20 merge.
> Could you guys pick it if it's OK?
>
>
> Thanks!
>
> Takashi
>
> >
> > >
> > >>
> > >> Fixes: 800efb4c2857 ("drm/nouveau/drm/therm/fan: add a fallback if no fan control is specified in the vbios")
> > >> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1103356
> > >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107447
> >
> > I see that Thomas has been having issues with the noise level anyway. I
> > suggest he should bump the value of temp1_auto_point1_temp (see
> > https://www.kernel.org/doc/Documentation/thermal/nouveau_thermal).
> >
> > The default value is set to 90°C which is quite safe on these old GPUs
> > (NVIDIA G71 / nv49). I would say that it is safe to go up to 110°C.
> > Which should reduce the noise level.
> >
> > Another technique may be to reduce the minimum fan speed to something
> > lower than 30°C. It should increase the slope but reduce the noise level
> > at a given temperature.
> >
> > One reason why these GPUs run so hot on nouveau is the lack of power and
> > clock gating. I am sorry that I never finished to reverse engineer these...
> >
> > Anyway, thanks a lot for the patch!
> >
> > >> Reported-by: Thomas Blume <thomas.blume at suse.com>
> > >> Signed-off-by: Takashi Iwai <tiwai at suse.de>
> > >>
> > >> ---
> > >>  drivers/gpu/drm/nouveau/nvkm/subdev/therm/base.c | 7 ++++---
> > >>  1 file changed, 4 insertions(+), 3 deletions(-)
> > >>
> > >> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/therm/base.c b/drivers/gpu/drm/nouveau/nvkm/subdev/therm/base.c
> > >> index 3695cde669f8..07914e36939e 100644
> > >> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/therm/base.c
> > >> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/therm/base.c
> > >> @@ -132,11 +132,12 @@ nvkm_therm_update(struct nvkm_therm *therm, int mode)
> > >>                         duty = nvkm_therm_update_linear(therm);
> > >>                         break;
> > >>                 case NVBIOS_THERM_FAN_OTHER:
> > >> -                       if (therm->cstate)
> > >> +                       if (therm->cstate) {
> > >>                                 duty = therm->cstate;
> > >> -                       else
> > >> +                               poll = false;
> > >> +                       } else {
> > >>                                 duty = nvkm_therm_update_linear_fallback(therm);
> > >> -                       poll = false;
> > >> +                       }
> > >>                         break;
> > >>                 }
> > >>                 immd = false;
> > >> --
> > >> 2.18.0
> > >>
> > >> _______________________________________________
> > >> Nouveau mailing list
> > >> Nouveau at lists.freedesktop.org
> > >> https://lists.freedesktop.org/mailman/listinfo/nouveau
> >
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