[Intel-gfx] [PATCH] drm/i915/dp: Add missing TPS4 programming bits

[Khaled Almahallawy]

Bits 20:19 are used to set CP2520 Patterns 1/2/3 (refer to Specs:50484).
TPS4 is CP2520 Pattern 3 (refer to DP2.0 spaces Table 3-11, DPCD 00248h
LINK_QUAL_PATTERN_SELECT, and DP PHY 1.4 CTS - Appendix A - Compliance
EYE Pattern(CP2520; Normative))

For TPS4, setting bits 20:19 to value != 00b, leads to a non-TPS4 pattern.
This is confirmed using DP Scope running DP1.4 PHY CTS.

To avoid any accidental wrong setting of bits 20:19, set it correctly for
TPS4 LT pattern selection. This programming sequence is the same used by EV.

Cc: Manasi Navare <manasi.d.navare at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
CC: José Roberto de Souza <jose.souza at intel.com>
Cc: Imre Deak <imre.deak at intel.com>
Signed-off-by: Khaled Almahallawy <khaled.almahallawy at intel.com>
---
 drivers/gpu/drm/i915/display/intel_ddi.c | 2 ++
 drivers/gpu/drm/i915/i915_reg.h          | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index 26a3aa73fcc4..54b4b28fdc74 100644
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -3412,6 +3412,8 @@ static void intel_ddi_set_link_train(struct intel_dp *intel_dp,
 		break;
 	case DP_TRAINING_PATTERN_4:
 		temp |= DP_TP_CTL_LINK_TRAIN_PAT4;
+		temp &= ~DP_TP_CTL_TRAIN_PAT4_SEL_MASK;
+		temp |= DP_TP_CTL_TRAIN_PAT4_SEL_TP4a;
 		break;
 	}
 
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 943fe485c662..a65998df9994 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -10176,6 +10176,10 @@ enum skl_power_gate {
 #define  DP_TP_CTL_MODE_SST			(0 << 27)
 #define  DP_TP_CTL_MODE_MST			(1 << 27)
 #define  DP_TP_CTL_FORCE_ACT			(1 << 25)
+#define  DP_TP_CTL_TRAIN_PAT4_SEL_MASK		(3 << 19)
+#define  DP_TP_CTL_TRAIN_PAT4_SEL_TP4a		(0 << 19)
+#define  DP_TP_CTL_TRAIN_PAT4_SEL_TP4b		(1 << 19)
+#define  DP_TP_CTL_TRAIN_PAT4_SEL_TP4c		(2 << 19)
 #define  DP_TP_CTL_ENHANCED_FRAME_ENABLE	(1 << 18)
 #define  DP_TP_CTL_FDI_AUTOTRAIN		(1 << 15)
 #define  DP_TP_CTL_LINK_TRAIN_MASK		(7 << 8)
-- 
2.25.1