On 1/29/2024 11:25 PM, Imre Deak wrote:
Add a workaround to fix BS jitter issues on MST links if the HBLANK
period is less than 1 MTP. The WA applies only to UHBR rates while on
non-UHBR the specification requires disabling it explicitly - presumedly
because the register's reset value has the WA enabled.
Bspec: 50050, 55424
Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
LGTM.
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>
---
drivers/gpu/drm/i915/display/intel_dp_mst.c | 8 ++++++++
drivers/gpu/drm/i915/i915_reg.h | 1 +
2 files changed, 9 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 22c1759f912db..23f3f7fab9d0b 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -1122,6 +1122,14 @@ static void enable_bs_jitter_was(const struct intel_crtc_state *crtc_state)
if (crtc_state->fec_enable || intel_dp_is_uhbr(crtc_state))
set |= DP_MST_FEC_BS_JITTER_WA(crtc_state->cpu_transcoder);
+ /* Wa_14014143976:adlp */
+ if (IS_DISPLAY_STEP(i915, STEP_E0, STEP_FOREVER)) {
+ if (intel_dp_is_uhbr(crtc_state))
+ set |= DP_MST_SHORT_HBLANK_WA(crtc_state->cpu_transcoder);
+ else if (crtc_state->fec_enable)
+ clear |= DP_MST_SHORT_HBLANK_WA(crtc_state->cpu_transcoder);
+ }
+
if (!clear && !set)
return;
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 67b7d02ea37bf..091edc1071e0e 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -4556,6 +4556,7 @@
#define GLK_CL0_PWR_DOWN REG_BIT(10)
#define CHICKEN_MISC_3 _MMIO(0x42088)
+#define DP_MST_SHORT_HBLANK_WA(trans) REG_BIT(5 + (trans) - TRANSCODER_A)
#define DP_MST_FEC_BS_JITTER_WA(trans) REG_BIT(0 + (trans) - TRANSCODER_A)
#define CHICKEN_MISC_4 _MMIO(0x4208c)
