lkml.org 
[lkml]   [2021]   [Jul]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH] drm/msm: Disable frequency clamping on a630
    On Thu, Jul 29, 2021 at 1:28 PM Caleb Connolly
    <caleb.connolly@linaro.org> wrote:
    >
    >
    >
    > On 29/07/2021 21:24, Rob Clark wrote:
    > > On Thu, Jul 29, 2021 at 1:06 PM Caleb Connolly
    > > <caleb.connolly@linaro.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.
    > Oh yeah that sounds like a more sensible workaround than mine .
    > >
    > > I'm slightly curious why I didn't have problems at higher OPPs on my
    > > c630 laptop (sdm850)
    > Perhaps you won the sillicon lottery - iirc sdm850 is binned for higher clocks as is out of the factory.
    >
    > Would it be best to drop the OPPs for all devices? Or just those affected? I guess it's possible another c630 might
    > crash where yours doesn't?

    I've not heard any reports of similar issues from the handful of other
    folks with c630's on #aarch64-laptops.. but I can't really say if that
    is luck or not.

    Maybe just remove it for affected devices? But I'll defer to Bjorn.

    BR,
    -R

    \
     
     \ /
      Last update: 2021-07-29 22:50    [W:3.205 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site