[PATCH] Revert "drm/amd/display: Revalidate bandwidth before commiting DC updates"

[Alex Deucher]

On Mon, Jun 29, 2020 at 12:13 PM Kazlauskas, Nicholas
<nicholas.kazlauskas at amd.com> wrote:
>
> On 2020-06-29 11:40 a.m., Kazlauskas, Nicholas wrote:
> > On 2020-06-29 11:36 a.m., Alex Deucher wrote:
> >> Seems to cause stability issues for some users.
> >>
> >> This reverts commit a24eaa5c51255b344d5a321f1eeb3205f2775498.
> >>
> >> Bug:
> >> https://gitlab.freedesktop.org/drm/amd/-/issues/1191
> >>
> >> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> >
> > I don't see the error in their log. How do we know this commit is
> > actually causing the issue?
> >
> > I don't really want to revert this commit because it means that we
> > missed rejecting a commit during atomic check, meaning we're either
> > going to get underflow on the screen or a pipe hang.
> >
> > Regards,
> > Nicholas Kazlauskas
>
> Actually, we only want to be doing this on full updates - it's not a
> very fast operation. Not sure if this is causing their stability issue
> though.

Maybe.  Several people have reported reverting it fixes hangs.  Maybe
something in the validation code hangs?  Maybe some sort of software
deadlock?

Alex


>
> Regards,
> Nicholas Kazlauskas
>
> >
> >> ---
> >>   drivers/gpu/drm/amd/display/dc/core/dc.c | 6 ------
> >>   1 file changed, 6 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c
> >> b/drivers/gpu/drm/amd/display/dc/core/dc.c
> >> index 67402d75e67e..94230bb3195d 100644
> >> --- a/drivers/gpu/drm/amd/display/dc/core/dc.c
> >> +++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
> >> @@ -2607,12 +2607,6 @@ void dc_commit_updates_for_stream(struct dc *dc,
> >>       copy_stream_update_to_stream(dc, context, stream, stream_update);
> >> -    if (!dc->res_pool->funcs->validate_bandwidth(dc, context, false)) {
> >> -        DC_ERROR("Mode validation failed for stream update!\n");
> >> -        dc_release_state(context);
> >> -        return;
> >> -    }
> >> -
> >>       commit_planes_for_stream(
> >>                   dc,
> >>                   srf_updates,
> >>
> >
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> >
>