[Intel-gfx] [PATCH] drm/i915: Display WA #1185 WaDisableDARBFClkGating:cnl, glk

[Rodrigo Vivi]

Display is not sending a PMRsp when a PMReq is received
at the same time that all planes are turned off.
State machine in the dcprunit is stuck in the WAIT4DONE
state which means that there is no fill_done.

WA: disable arbiter clock gating, set bit [27] of 0x46530

v2: As Ville pointed out, based on the description the issue
    can happen when disabling the planes, similar to
    WaRsPkgCStateDisplayPMReq:hsw
    Also description of the issue was updated on commit
    message to make it more clear that we need this
    earlier.
v3: Restore comment about possibility to system hang
    to where we are sure about it, without speculation. (Ville).

Cc: Radhakrishna Sripada <radhakrishna.sripada at intel.com>
Cc: Imre Deak <imre.deak at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h      |  1 +
 drivers/gpu/drm/i915/intel_display.c | 24 +++++++++++++++---------
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 6ef33422f762..fc8c5f8260f6 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3819,6 +3819,7 @@ enum {
  * GEN9 clock gating regs
  */
 #define GEN9_CLKGATE_DIS_0		_MMIO(0x46530)
+#define   DARBF_GATING_DIS		(1 << 27)
 #define   PWM2_GATING_DIS		(1 << 14)
 #define   PWM1_GATING_DIS		(1 << 13)
 
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 5c7540f3f5dc..282a4664a517 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15081,6 +15081,20 @@ get_encoder_power_domains(struct drm_i915_private *dev_priv)
 	}
 }
 
+/* System hang if this isn't done before disabling all planes! */
+static void intel_early_display_was(struct drm_i915_private *dev_priv)
+{
+	/* Display WA #1185 WaDisableDARBFClkGating:cnl,glk */
+	if (IS_CANNONLAKE(dev_priv) || IS_GEMINILAKE(dev_priv))
+		I915_WRITE(GEN9_CLKGATE_DIS_0, I915_READ(GEN9_CLKGATE_DIS_0) |
+			   DARBF_GATING_DIS);
+
+	/* WaRsPkgCStateDisplayPMReq:hsw */
+	if (IS_HASWELL(dev_priv))
+		I915_WRITE(CHICKEN_PAR1_1,
+			   I915_READ(CHICKEN_PAR1_1) | FORCE_ARB_IDLE_PLANES);
+}
+
 /* Scan out the current hw modeset state,
  * and sanitizes it to the current state
  */
@@ -15094,15 +15108,7 @@ intel_modeset_setup_hw_state(struct drm_device *dev,
 	struct intel_encoder *encoder;
 	int i;
 
-	if (IS_HASWELL(dev_priv)) {
-		/*
-		 * WaRsPkgCStateDisplayPMReq:hsw
-		 * System hang if this isn't done before disabling all planes!
-		 */
-		I915_WRITE(CHICKEN_PAR1_1,
-			   I915_READ(CHICKEN_PAR1_1) | FORCE_ARB_IDLE_PLANES);
-	}
-
+	intel_early_display_was(dev_priv);
 	intel_modeset_readout_hw_state(dev);
 
 	/* HW state is read out, now we need to sanitize this mess. */
-- 
2.13.6