NAK: [H/I/Unstable/OEM-5.13] [PATCH 1/1] UBUNTU: SAUCE: drm/i915/dp: Use max params for older panels

[Kai-Heng Feng]

On Wed, Sep 1, 2021 at 5:47 PM Kleber Souza <kleber.souza at canonical.com> wrote:
>
> On 09.08.21 07:09, Kai-Heng Feng wrote:
> > BugLink: https://bugs.launchpad.net/bugs/1936708
> >
> > Users reported that after commit 2bbd6dba84d4 ("drm/i915: Try to use
> > fast+narrow link on eDP again and fall back to the old max strategy on
> > failure"), the screen starts to have wobbly effect.
> >
> > Commit a5c936add6a2 ("drm/i915/dp: Use slow and wide link training for
> > everything") doesn't help either, that means the affected panels only
> > work with max params.
> >
> > The panels are all DP 1.1 ones, so apply max params to them to resolve
> > the issue.
> >
> > Link: https://patchwork.kernel.org/project/intel-gfx/list/?series=526397
> > Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/3714
> > Fixes: 2bbd6dba84d4 ("drm/i915: Try to use fast+narrow link on eDP again and fall back to the old max strategy on failure")
> > Fixes: a5c936add6a2 ("drm/i915/dp: Use slow and wide link training for everything")
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>
> > ---
> >   drivers/gpu/drm/i915/display/intel_dp.c | 12 +++++++-----
> >   1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 6cc03b9e4321a..eb1ed8990ca03 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -1338,14 +1338,16 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
> >       limits.min_bpp = intel_dp_min_bpp(pipe_config->output_format);
> >       limits.max_bpp = intel_dp_max_bpp(intel_dp, pipe_config);
> >
> > -     if (intel_dp->use_max_params) {
> > +     if (intel_dp->use_max_params ||
> > +         intel_dp->dpcd[DP_DPCD_REV] <= DP_DPCD_REV_11) {
> >               /*
> >                * Use the maximum clock and number of lanes the eDP panel
> >                * advertizes being capable of in case the initial fast
> > -              * optimal params failed us. The panels are generally
> > -              * designed to support only a single clock and lane
> > -              * configuration, and typically on older panels these
> > -              * values correspond to the native resolution of the panel.
> > +              * optimal params failed us or the panel is DP 1.1 or earlier.
> > +              * The panels are generally designed to support only a single
> > +              * clock and lane configuration, and typically on older panels
> > +              * these values correspond to the native resolution of the
> > +              * panel.
> >                */
> >               limits.min_lane_count = limits.max_lane_count;
> >               limits.min_clock = limits.max_clock;
> >
>
> What ended up being accepted, at least in drm-intel-next for now, was a v3
> of this patch fixing some corner cases not spotted on this first version:
>
> https://cgit.freedesktop.org/drm/drm-intel/commit/?h=drm-intel-next&id=d7f213c131adf0bec8b731553eb82990cdac265d
>
> So I'm NAKing it for any stable releases until we have v3 backported/cherry-picked
> and submitted again.
>
> Also, what should we do about I/U/OEM-5.13 which already got the incomplete
> version of the fix?

I'll send another SRU to replace the old fix with the one in upstream.

Kai-Heng

>
>
> Kleber