[Intel-gfx] [PATCH 14/15] drm/i915: skl nv12 wa - NV12 to RGB switch

[Chandra Konduru]

Switching format from NV12 to RGB can result in display underrun
and corruption. This workaround sets bits 15 & 19 to 1 in
CLKGATE_DIS_PSL register to address transition underrun.

v2:
-Move workaround to init clock gating (Ville)

Signed-off-by: Chandra Konduru <chandra.konduru at intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h |    8 ++++++++
 drivers/gpu/drm/i915/intel_pm.c |    8 ++++++++
 2 files changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index d20f235..2e2636d 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -5366,6 +5366,14 @@ enum skl_disp_power_wells {
 #define CHICKEN_DCPR_1             0x46430
 #define IDLE_WAKEMEM_MASK          (1 << 13)
 
+#define CLKGATE_DIS_PSL_A        0x46520
+#define CLKGATE_DIS_PSL_B        0x46524
+#define CLKGATE_DIS_PSL_C        0x46528
+#define DUPS1_GATING_DIS         (1 << 15)
+#define DUPS2_GATING_DIS         (1 << 19)
+#define DUPS3_GATING_DIS         (1 << 23)
+#define CLKGATE_DIS_PSL(pipe)  _PIPE(pipe, CLKGATE_DIS_PSL_A, CLKGATE_DIS_PSL_B)
+
 /* SKL new cursor registers */
 #define _CUR_BUF_CFG_A				0x7017c
 #define _CUR_BUF_CFG_B				0x7117c
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 8a36ab9..9a3deed 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -63,6 +63,14 @@ static void gen9_init_clock_gating(struct drm_device *dev)
 	/* WaDisableKillLogic:bxt,skl */
 	I915_WRITE(GAM_ECOCHK, I915_READ(GAM_ECOCHK) |
 		   ECOCHK_DIS_TLB);
+
+	/*
+	 * Switching format from NV12 to RGB can result in display underrun
+	 * and corruption. This workaround sets bits 15 & 19 to 1 in
+	 * CLKGATE_DIS_PSL register to address transition underrun.
+	 */
+	I915_WRITE(CLKGATE_DIS_PSL(PIPE_A), DUPS1_GATING_DIS | DUPS2_GATING_DIS);
+	I915_WRITE(CLKGATE_DIS_PSL(PIPE_B), DUPS1_GATING_DIS | DUPS2_GATING_DIS);
 }
 
 static void skl_init_clock_gating(struct drm_device *dev)
-- 
1.7.9.5