[PATCH v8 10/13] drm/i915/display: Evade scanline 0 as well if PSR1 or PSR2 is enabled

[Jouni Högander]

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.

v2:
  - use intel_dsb_emit_wait_dsl
  - add evasion of scanline 0 also for Panel Replay

Signed-off-by: Jouni Högander <jouni.hogander at intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 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 4c067bf9ac4c..9fc4003d1579 100644
--- a/drivers/gpu/drm/i915/display/intel_dsb.c
+++ b/drivers/gpu/drm/i915/display/intel_dsb.c
@@ -564,6 +564,18 @@ 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)
+		intel_dsb_emit_wait_dsl(dsb, DSB_OPCODE_WAIT_DSL_OUT, 0, 0);
+
 	if (pre_commit_is_vrr_active(state, crtc)) {
 		int vblank_delay = intel_vrr_vblank_delay(crtc_state);
 
-- 
2.43.0