On Monday, September 21, 2026 5:43:31 PM Central European Summer Time Mario
Limonciello wrote:
> On 9/21/26 10:33, Mario Limonciello wrote:
> > On 9/21/26 05:41, Timur Kristóf wrote:
> >> DCE6 should use legacy fast updates, just like all DCE8 - DCN2.
> >>
> >> Technically DCE6 should have been included when the fast update
> >> code was refactored, but it just happened to work until now.
> >>
> >> A recent commit "Attach only plane updates that actually changed"
> >> has exposed this issue because with that commit, DC accidentally
> >> took the new fast update code path for DCE6 as well, which caused
> >> it to boot into a black screen with a flip done timeout.
> >>
> >> This fix should be backported to all kernel versions that
> >> have "Refactor fast update to use new HWSS build sequence",
> >> but this patch won't apply cleanly to older kernels due to
> >> another refactor in "Remove dc param from check_update".
> >>
> >> Fixes: 0baae6246307 ("drm/amd/display: Refactor fast update to use new
> >> HWSS build sequence")
> >> Fixes: 9ec11bb842b6 ("drm/amd/display: Remove dc param from
> >> check_update")
> >> Signed-off-by: Timur Kristóf <[email protected]>
> >
> > Reviewed-by: Mario Limonciello <[email protected]>> ---
> >
> >> .../drm/amd/display/dc/resource/dce60/dce60_resource.c | 8 ++++++++
> >> 1 file changed, 8 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/amd/display/dc/resource/dce60/
> >> dce60_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dce60/
> >> dce60_resource.c
> >> index d2d56a1c4b8b..f4efa55952f3 100644
> >> --- a/drivers/gpu/drm/amd/display/dc/resource/dce60/dce60_resource.c
> >> +++ b/drivers/gpu/drm/amd/display/dc/resource/dce60/dce60_resource.c
> >> @@ -448,6 +448,12 @@ static const struct dce_abm_mask abm_mask = {
> >> ABM_MASK_SH_LIST_DCE110(_MASK)
> >> };
> >> +static const struct dc_debug_options debug_defaults = { 0 };
> >> +
> >> +static const struct dc_check_config config_defaults = {
> >> + .enable_legacy_fast_update = true,
> >> +};
> >> +
> >> #define CTX ctx
> >> #define REG(reg) mm ## reg
> >> @@ -937,6 +943,8 @@ static bool dce60_construct(
> >> dc->caps.max_cursor_size = 64;
> >> dc->caps.dual_link_dvi = true;
> >> dc->caps.extended_aux_timeout_support = false;
> >> + dc->debug = debug_defaults;
> >> + dc->check_config = config_defaults;
> >> /*************************************************
> >> * Create resources *
>
> I would be remiss not to share something the code-review agent flagged
> when testing this for merge.
>
> ---
> Incomplete fix: this is only dce60_construct(), which
> dc_create_resource_pool() uses for DCE_VERSION_6_0 (Tahiti / Pitcairn /
> Cape Verde) only.
>
> dce60_resource.c has two more constructors that are reached for the
> other SI parts (see resource_parse_asic_id() in core/dc_resource.c:150-158):
>
> dce61_construct() (line 1120) -> DCE_VERSION_6_1 (Hainan)
> dce64_construct() (line 1318) -> DCE_VERSION_6_4 (Oland)
> Neither gets dc->check_config assigned, so enable_legacy_fast_update
> stays false there (dc is kvzalloc'd in dc_create()), and both keep
> taking the new fast-update path that ac8349780c5d exposes. They should
> hit exactly the same black screen / flip-done timeout this patch is
> fixing, since all three share dce60_hw_sequencer_construct() and
> dce60_res_pool_funcs.
>
> Suggest adding the same two lines to both, e.g. after dc->caps.is_apu =
> true; at line 1144 (dce61) and line 1342 (dce64):
>
> dc->debug = debug_defaults;
> dc->check_config = config_defaults;
> ---
>
> I'll hold up the merge to decide what to do (we can just have a v2 if
> you want).
Thanks for calling that out. I'll send a second version.
