[Intel-gfx] [PATCH] drm/i915: Apply Wa Display #1183 on skl, kbl, and cfl.

[Rodrigo Vivi]

Wa Display #1183 was recently added to workaround
"Failures when enabling DPLL0 with eDP link rate 2.16
or 4.32 GHz and CD clock frequency 308.57 or 617.14 MHz
(CDCLK_CTL CD Frequency Select 10b or 11b) used in this
 enabling or in previous enabling."

However our code is already not following the
"Skylake Seqyences to Initialize Display" line by line
so it was really hard to map this workaround there.

The biggest difference is that Spec sequence expect that
by the time we are enabling DPLL0 we already know the
eDP link rate. What it is not true for us. We handle eDP
link rate as any other DP link rate at the modeset. With
only one small difference that we check a VCO when that
is available.

WARN: It seems that DPLL0 link rate was not designed to
change on the fly and we will probably need to find a more
robuts solution caching the eDP link rate somehow.

This Workaround was designed to minimize the impact only
to save the bad case with that link rates. But HW engineers
indicated that it should be safe to apply broadly. Although
they were expecting the DPLL0 link rate to be unchanged on
runtime.

Cc: Arthur J Runyan <arthur.j.runyan at intel.com>
Cc: 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         |  2 ++
 drivers/gpu/drm/i915/intel_cdclk.c      | 33 +++++++++++++++++++++++++++------
 drivers/gpu/drm/i915/intel_runtime_pm.c | 10 ++++++++++
 3 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 5f99d4d6291b..446f4b6fade1 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -6980,6 +6980,7 @@ enum {
 #define  RESET_PCH_HANDSHAKE_ENABLE	(1<<4)
 
 #define GEN8_CHICKEN_DCPR_1		_MMIO(0x46430)
+#define   SKL_SELECT_ALTERNATE_DC_EXIT	(1<<30)
 #define   MASK_WAKEMEM			(1<<13)
 
 #define SKL_DFSM			_MMIO(0x51000)
@@ -8525,6 +8526,7 @@ enum skl_power_gate {
 #define  BXT_CDCLK_CD2X_DIV_SEL_4	(3<<22)
 #define  BXT_CDCLK_CD2X_PIPE(pipe)	((pipe)<<20)
 #define  BXT_CDCLK_CD2X_PIPE_NONE	BXT_CDCLK_CD2X_PIPE(3)
+#define  DIVMUX_CD_OVERRIDE		(1<<19)
 #define  BXT_CDCLK_SSA_PRECHARGE_ENABLE	(1<<16)
 #define  CDCLK_FREQ_DECIMAL_MASK	(0x7ff)
 
diff --git a/drivers/gpu/drm/i915/intel_cdclk.c b/drivers/gpu/drm/i915/intel_cdclk.c
index b2a6d62b71c0..e193912b21ec 100644
--- a/drivers/gpu/drm/i915/intel_cdclk.c
+++ b/drivers/gpu/drm/i915/intel_cdclk.c
@@ -858,7 +858,8 @@ static void skl_set_preferred_cdclk_vco(struct drm_i915_private *dev_priv,
 		intel_update_max_cdclk(dev_priv);
 }
 
-static void skl_dpll0_enable(struct drm_i915_private *dev_priv, int vco)
+static void skl_dpll0_enable(struct drm_i915_private *dev_priv, int vco,
+			     u32 freq_select)
 {
 	int min_cdclk = skl_calc_cdclk(0, vco);
 	u32 val;
@@ -894,6 +895,11 @@ static void skl_dpll0_enable(struct drm_i915_private *dev_priv, int vco)
 	I915_WRITE(DPLL_CTRL1, val);
 	POSTING_READ(DPLL_CTRL1);
 
+	/* Wa Display #1183: skl,kbl,cfl */
+	val = I915_READ(CDCLK_CTL);
+	val |= DIVMUX_CD_OVERRIDE;
+	I915_WRITE(CDCLK_CTL, val);
+
 	I915_WRITE(LCPLL1_CTL, I915_READ(LCPLL1_CTL) | LCPLL_PLL_ENABLE);
 
 	if (intel_wait_for_register(dev_priv,
@@ -901,6 +907,18 @@ static void skl_dpll0_enable(struct drm_i915_private *dev_priv, int vco)
 				    5))
 		DRM_ERROR("DPLL0 not locked\n");
 
+	/* Wa Display #1183: skl,kbl,cfl */
+	val = I915_READ(CDCLK_CTL);
+	val &= ~CDCLK_FREQ_SEL_MASK;;
+	I915_WRITE(CDCLK_CTL, val);
+
+	I915_WRITE(CDCLK_CTL, freq_select);
+	POSTING_READ(CDCLK_CTL);
+
+	val = I915_READ(CDCLK_CTL);
+	val &= ~DIVMUX_CD_OVERRIDE;
+	I915_WRITE(CDCLK_CTL, val);
+
 	dev_priv->cdclk.hw.vco = vco;
 
 	/* We'll want to keep using the current vco from now on. */
@@ -964,15 +982,18 @@ static void skl_set_cdclk(struct drm_i915_private *dev_priv,
 		break;
 	}
 
+	freq_select |= skl_cdclk_decimal(cdclk);
+
 	if (dev_priv->cdclk.hw.vco != 0 &&
 	    dev_priv->cdclk.hw.vco != vco)
 		skl_dpll0_disable(dev_priv);
 
-	if (dev_priv->cdclk.hw.vco != vco)
-		skl_dpll0_enable(dev_priv, vco);
-
-	I915_WRITE(CDCLK_CTL, freq_select | skl_cdclk_decimal(cdclk));
-	POSTING_READ(CDCLK_CTL);
+	if (dev_priv->cdclk.hw.vco != vco) {
+		skl_dpll0_enable(dev_priv, vco, freq_select);
+	} else {
+		I915_WRITE(CDCLK_CTL, freq_select);
+		POSTING_READ(CDCLK_CTL);
+	}
 
 	/* inform PCU of the change */
 	mutex_lock(&dev_priv->pcu_lock);
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 8af286c63d3b..e0bc2debdad0 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -598,6 +598,11 @@ void gen9_enable_dc5(struct drm_i915_private *dev_priv)
 
 	DRM_DEBUG_KMS("Enabling DC5\n");
 
+	/* Wa Display #1183: skl,kbl,cfl */
+	if (IS_GEN9_BC(dev_priv))
+		I915_WRITE(GEN8_CHICKEN_DCPR_1, I915_READ(GEN8_CHICKEN_DCPR_1) |
+			   SKL_SELECT_ALTERNATE_DC_EXIT);
+
 	gen9_set_dc_state(dev_priv, DC_STATE_EN_UPTO_DC5);
 }
 
@@ -625,6 +630,11 @@ void skl_disable_dc6(struct drm_i915_private *dev_priv)
 {
 	DRM_DEBUG_KMS("Disabling DC6\n");
 
+	/* Wa Display #1183: skl,kbl,cfl */
+	if (IS_GEN9_BC(dev_priv))
+		I915_WRITE(GEN8_CHICKEN_DCPR_1, I915_READ(GEN8_CHICKEN_DCPR_1) |
+			   SKL_SELECT_ALTERNATE_DC_EXIT);
+
 	gen9_set_dc_state(dev_priv, DC_STATE_DISABLE);
 }
 
-- 
2.13.5