On Fri, 2025-01-24 at 14:49 +0200, Ville Syrjälä wrote: > On Fri, Jan 24, 2025 at 12:41:11PM +0000, Hogander, Jouni wrote: > > On Fri, 2025-01-24 at 14:37 +0200, Ville Syrjälä wrote: > > > On Fri, Jan 24, 2025 at 11:57:10AM +0000, Hogander, Jouni wrote: > > > > On Fri, 2025-01-24 at 13:39 +0200, Ville Syrjälä wrote: > > > > > On Fri, Jan 24, 2025 at 12:56:22PM +0200, Jouni Högander > > > > > wrote: > > > > > > PIPEDSL is reading as 0 when in SRDENT(PSR1) or > > > > > > DEEP_SLEEP(PSR2). > > > > > > On > > > > > > wake-up scanline counting starts from vblank_start - 1. We > > > > > > don't > > > > > > know if > > > > > > wake-up is already ongoing when evasion starts. In worst > > > > > > case > > > > > > PIPEDSL could > > > > > > start reading valid value right after checking the > > > > > > scanline. In > > > > > > this > > > > > > scenario we wouldn't have enough time to write all > > > > > > registers. > > > > > > To > > > > > > tackle > > > > > > this evade scanline 0 as well. As a drawback we have 1 > > > > > > frame > > > > > > delay > > > > > > in flip > > > > > > when waking up. > > > > > > > > > > > > Signed-off-by: Jouni Högander <jouni.hogander@xxxxxxxxx> > > > > > > --- > > > > > > drivers/gpu/drm/i915/display/intel_dsb.c | 12 ++++++++++++ > > > > > > 1 file changed, 12 insertions(+) > > > > > > > > > > > > diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c > > > > > > b/drivers/gpu/drm/i915/display/intel_dsb.c > > > > > > index bb77ded8bf726..914f0be4491c4 100644 > > > > > > --- a/drivers/gpu/drm/i915/display/intel_dsb.c > > > > > > +++ b/drivers/gpu/drm/i915/display/intel_dsb.c > > > > > > @@ -528,6 +528,18 @@ void intel_dsb_vblank_evade(struct > > > > > > intel_atomic_state *state, > > > > > > int latency = > > > > > > intel_usecs_to_scanlines(&crtc_state- > > > > > > > hw.adjusted_mode, 20); > > > > > > int start, end; > > > > > > > > > > > > + /* > > > > > > + * PIPEDSL is reading as 0 when in SRDENT(PSR1) or > > > > > > DEEP_SLEEP(PSR2). On > > > > > > + * wake-up scanline counting starts from > > > > > > vblank_start > > > > > > - 1. > > > > > > We don't know > > > > > > + * if wake-up is already ongoing when evasion > > > > > > starts. > > > > > > In > > > > > > worst case > > > > > > + * PIPEDSL could start reading valid value right > > > > > > after > > > > > > checking the > > > > > > + * scanline. In this scenario we wouldn't have > > > > > > enough > > > > > > time > > > > > > to write all > > > > > > + * registers. To tackle this evade scanline 0 as > > > > > > well. > > > > > > As > > > > > > a drawback we > > > > > > + * have 1 frame delay in flip when waking up. > > > > > > + */ > > > > > > + if (crtc_state->has_psr && !crtc_state- > > > > > > > has_panel_replay) > > > > > > > > > > What's the deal with panel replay here? > > > > > > > > I couldn't see PIPEDSL returning 0 when using Panel Replay. > > > > Even on > > > > same setup with PSR I saw it, but with PR I couldn't see. > > > > > > Hmm. Are you sure it's reaching DC5/6? > > > > > > Though I suppose it's possible that panel replay (unlike PSR) > > > does pretty much everything from the DMC's DC state handler, > > > so as soon as you read the register it restores things fully > > > enough that you get the vblank_start-1 response... > > > > Maybe we just add that evasion without checking panel replay. It > > shouldn't be too expensive anyways. What do you think? > > Yeah, that seems fine to me. > > But I still think you should try to double check that it > really reaches DC6 with panel replay despite PIPDSL not > getting reset, so that we at least understand a bit better > what is actually happening. Here are my observations: 1. TGL/PSR2, no DMC firmware : PIPEDSL is reading as vblank - 1 when in DEEP_SLEEP 2. TGL/PSR2, DMC firmware loaded: PIPEDSL is reading as 0 when in DEEP_SLEEP 3. TGL/PSR2, DMC fimware loaded , DC states disabled : PIPEDSL reading is running all the time 4. LNL/Panel Replay, no DMC firmware : PIPEDSL reading is running all the time 5. LNL/Panel Replay, DMC firmware loaded : PIPEDSL is reading as vblank - 1 when in SLEEP 6. LNL/Panel Replay, DMC firmware loaded, DC state disabled : PIPEDSL reading is running all the time Results are differing. Based on this: Current evation is handling cases where PIPEDSL reading is running or vblank - 1. PIPEDSL reading as 0 is handled by this adding scanline 0 evation. PSR2 commits not using DSB currently might be actually affected by your concern. I.e. wake-up is already ongoing when performing vblank evation. PSR1 shouldn't have this problem as there we are waiting PSR state to become idle. Maybe we should add scanline 0 there as well? Not related to this patch though. BR, Jouni Högander >
