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Message-ID: <CAF6AEGs5dzA7kfO89Uqbh3XmorXoEa=fpW+unk5_oaihHm479Q@mail.gmail.com>
Date: Thu, 29 Jul 2021 13:24:25 -0700
From: Rob Clark <robdclark@...il.com>
To: Caleb Connolly <caleb.connolly@...aro.org>
Cc: dri-devel <dri-devel@...ts.freedesktop.org>,
freedreno <freedreno@...ts.freedesktop.org>,
linux-arm-msm <linux-arm-msm@...r.kernel.org>,
Rob Clark <robdclark@...omium.org>,
Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
Jordan Crouse <jordan@...micpenguin.net>,
Jonathan Marek <jonathan@...ek.ca>,
Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
Bjorn Andersson <bjorn.andersson@...aro.org>,
Sharat Masetty <smasetty@...eaurora.org>,
Akhil P Oommen <akhilpo@...eaurora.org>,
open list <linux-kernel@...r.kernel.org>,
Stephen Boyd <sboyd@...nel.org>
Subject: Re: [PATCH] drm/msm: Disable frequency clamping on a630
On Thu, Jul 29, 2021 at 1:06 PM Caleb Connolly
<caleb.connolly@...aro.org> wrote:
>
> Hi Rob,
>
> I've done some more testing! It looks like before that patch ("drm/msm: Devfreq tuning") the GPU would never get above
> the second frequency in the OPP table (342MHz) (at least, not in glxgears). With the patch applied it would more
> aggressively jump up to the max frequency which seems to be unstable at the default regulator voltages.
*ohh*, yeah, ok, that would explain it
> Hacking the pm8005 s1 regulator (which provides VDD_GFX) up to 0.988v (instead of the stock 0.516v) makes the GPU stable
> at the higher frequencies.
>
> Applying this patch reverts the behaviour, and the GPU never goes above 342MHz in glxgears, losing ~30% performance in
> glxgear.
>
> I think (?) that enabling CPR support would be the proper solution to this - that would ensure that the regulators run
> at the voltage the hardware needs to be stable.
>
> Is hacking the voltage higher (although ideally not quite that high) an acceptable short term solution until we have
> CPR? Or would it be safer to just not make use of the higher frequencies on a630 for now?
>
tbh, I'm not sure about the regulator stuff and CPR.. Bjorn is already
on CC and I added sboyd, maybe one of them knows better.
In the short term, removing the higher problematic OPPs from dts might
be a better option than this patch (which I'm dropping), since there
is nothing stopping other workloads from hitting higher OPPs.
I'm slightly curious why I didn't have problems at higher OPPs on my
c630 laptop (sdm850)
BR,
-R
>
> On 29/07/2021 19:39, Rob Clark wrote:
> > From: Rob Clark <robdclark@...omium.org>
> >
> > The more frequent frequency transitions resulting from clamping freq to
> > minimum when the GPU is idle seems to be causing some issue with the bus
> > getting voted off when it should be on. (An enable racing with an async
> > disable?) This might be a problem outside of the GPU, as I can't
> > reproduce this on a618 which uses the same GMU fw and same mechanism to
> > communicate with GMU to set opp. For now, just revert to previous
> > devfreq behavior on a630 until the issue is understood.
> >
> > Reported-by: Caleb Connolly <caleb.connolly@...aro.org>
> > Fixes: 9bc95570175a ("drm/msm: Devfreq tuning")
> > Signed-off-by: Rob Clark <robdclark@...omium.org>
> > ---
> > drivers/gpu/drm/msm/adreno/adreno_gpu.c | 3 +++
> > drivers/gpu/drm/msm/msm_gpu.h | 2 ++
> > drivers/gpu/drm/msm/msm_gpu_devfreq.c | 12 ++++++++++++
> > 3 files changed, 17 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> > index 748665232d29..9fd08b413010 100644
> > --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> > +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> > @@ -945,6 +945,9 @@ int adreno_gpu_init(struct drm_device *drm, struct platform_device *pdev,
> > pm_runtime_use_autosuspend(dev);
> > pm_runtime_enable(dev);
> >
> > + if (adreno_is_a630(adreno_gpu))
> > + gpu->devfreq.disable_freq_clamping = true;
> > +
> > return msm_gpu_init(drm, pdev, &adreno_gpu->base, &funcs->base,
> > adreno_gpu->info->name, &adreno_gpu_config);
> > }
> > diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
> > index 0e4b45bff2e6..7e11b667f939 100644
> > --- a/drivers/gpu/drm/msm/msm_gpu.h
> > +++ b/drivers/gpu/drm/msm/msm_gpu.h
> > @@ -112,6 +112,8 @@ struct msm_gpu_devfreq {
> > * it is inactive.
> > */
> > unsigned long idle_freq;
> > +
> > + bool disable_freq_clamping;
> > };
> >
> > struct msm_gpu {
> > diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
> > index 0a1ee20296a2..a832af436251 100644
> > --- a/drivers/gpu/drm/msm/msm_gpu_devfreq.c
> > +++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
> > @@ -94,6 +94,12 @@ void msm_devfreq_init(struct msm_gpu *gpu)
> > if (!gpu->funcs->gpu_busy)
> > return;
> >
> > + /* Revert to previous polling interval if we aren't using freq clamping
> > + * to preserve previous behavior
> > + */
> > + if (gpu->devfreq.disable_freq_clamping)
> > + msm_devfreq_profile.polling_ms = 10;
> > +
> > msm_devfreq_profile.initial_freq = gpu->fast_rate;
> >
> > /*
> > @@ -151,6 +157,9 @@ void msm_devfreq_active(struct msm_gpu *gpu)
> > unsigned int idle_time;
> > unsigned long target_freq = df->idle_freq;
> >
> > + if (gpu->devfreq.disable_freq_clamping)
> > + return;
> > +
> > /*
> > * Hold devfreq lock to synchronize with get_dev_status()/
> > * target() callbacks
> > @@ -186,6 +195,9 @@ void msm_devfreq_idle(struct msm_gpu *gpu)
> > struct msm_gpu_devfreq *df = &gpu->devfreq;
> > unsigned long idle_freq, target_freq = 0;
> >
> > + if (gpu->devfreq.disable_freq_clamping)
> > + return;
> > +
> > /*
> > * Hold devfreq lock to synchronize with get_dev_status()/
> > * target() callbacks
> >
>
> --
> Kind Regards,
> Caleb (they/them)
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