[PATCH] Revert "drm/amd/display: limit clear_update_flags to dcn32 and above"

[Matthew Schwartz]

On Thu, Jul 17, 2025 at 12:18 PM Melissa Wen <mwen at igalia.com> wrote:
>
> On 17-07-2025 17:57, Matthew Schwartz wrote:
> >> On Jul 17, 2025, at 9:58 AM, Limonciello, Mario <Mario.Limonciello at amd.com> wrote:
> >>
> >> On 7/17/25 11:55 AM, Melissa Wen wrote:
> >>> On 17-07-2025 13:39, Limonciello, Mario wrote:
> >>>> On 7/17/25 9:36 AM, Melissa Wen wrote:
> >>>>> This reverts commit e1bd5e0bb4ca0d633ad698abd3658f8265009b81.
> >>>>>
> >>>>> The commit causes a regression in Steam Deck (DCN 3.01), reintroducing a
> >>>>> functional issue reported in [1] that was fixed by calling the
> >>>>> clear_update_flags() from commit 7671f62c10f2a.
> >>>>>
> >>>>> On Steam Deck, we use multiple hw plane color caps and up to two overlay
> >>>>> planes with dynamic pipe split policy. I.e. with 1 primary + 1 overlay,
> >>>>> the driver split planes into two (with 4 pipes), but with 1 primary + 2
> >>>>> overlays, we don't have enough pipe for splitting. Glitches appear in
> >>>>> this pipe-split transition of 1-2 overlay planes, if the driver doesn't
> >>>>> clear update flags.
> >>>>>
> >>>>> Besides that, the issue the commit e1bd5e0bb4ca tries to address [2]
> >>>>> isn't functional.
> >>>>>
> >>>>> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/3441 [1]
> >>>>> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/4129 [2]
> >>>>> Signed-off-by: Melissa Wen <mwen at igalia.com>
> >>>>
> >>>> Can you please double check the use case that prompted
> >>>> e1bd5e0bb4ca0d633ad698abd3658f8265009b81 in the first place?  IE With
> >>>> this revert you proposed do you see a traceback on unplug of external
> >>>> display?
> >>>
> >>> Hi Mario,
> >>>
> >>> I don't see either traceback or REG_WAIT timeout when unplugging an
> >>> external HDMI-connected display.
> >>> I tried with the Deck Dock and USB-C to HDMI adapter. Not sure if there
> >>> is a very specific scenario that triggers this that I didn't cover.
> >>
> >> No; it's quite a general problem and easy to reproduce.  This makes me
> >> wonder if there should be an exception carved out for Steam Deck instead.
> >
> > I just tested DCN 3.1.2 (Z2 Go) and DCN 3.1.4 (Legion Go/ROG Ally) and
> > I was not able to reproduce the issue so a Steam Deck carveout might make
> > sense here.
>
> What issue are you trying to reproduce?
> Glitches on Hades II + MangoHud, or traceback/REG_WAIT timeout?

Sorry, should've specified! I was testing for glitches with Hades II + MangoHud.

>
> And with what kernel version?

amd-staging-drm-next built from b78bd800, tested on top of SteamOS Main

>
> Melissa
>
> >
> > Matt
> >
> >>
> >>>
> >>> The only message on dmesg from this action is:
> >>> amdgpu 0000:04:00.0: amdgpu: pp_od_clk_voltage is not accessible if
> >>> power_dpm_force_performance_level is not in manual mode!
> >>>
> >>> Moreover, if I move to the Desktop mode (KDE), there is no message.
> >>>
> >>> Melissa
> >>>
> >>>>
> >>>>> ---
> >>>>>   drivers/gpu/drm/amd/display/dc/core/dc.c | 5 +++--
> >>>>>   1 file changed, 3 insertions(+), 2 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
> >>>>> index c31f7f8e409f..7c48f72e5917 100644
> >>>>> --- a/drivers/gpu/drm/amd/display/dc/core/dc.c
> >>>>> +++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
> >>>>> @@ -5443,7 +5443,8 @@ bool dc_update_planes_and_stream(struct dc *dc,
> >>>>>    else
> >>>>>    ret = update_planes_and_stream_v2(dc, srf_updates,
> >>>>>    surface_count, stream, stream_update);
> >>>>> - if (ret && dc->ctx->dce_version >= DCN_VERSION_3_2)
> >>>>> +
> >>>>> + if (ret)
> >>>>>    clear_update_flags(srf_updates, surface_count, stream);
> >>>>>
> >>>>>    return ret;
> >>>>> @@ -5474,7 +5475,7 @@ void dc_commit_updates_for_stream(struct dc *dc,
> >>>>>    ret = update_planes_and_stream_v1(dc, srf_updates, surface_count, stream,
> >>>>>    stream_update, state);
> >>>>>
> >>>>> - if (ret && dc->ctx->dce_version >= DCN_VERSION_3_2)
> >>>>> + if (ret)
> >>>>>    clear_update_flags(srf_updates, surface_count, stream);
> >>>>>   }