[PATCH 4/5] drm/i915/kbl+: Enable IPC only for symmetric memory configurations

[Mahesh Kumar <mahesh1.kumar@xxxxxxxxx>]

IPC may cause underflows if not used with dual channel symmetric
memory configuration. Disable IPC for non symmetric configurations in
affected platforms.
Display WA #1141

Signed-off-by: Mahesh Kumar <mahesh1.kumar@xxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_drv.c | 43 ++++++++++++++++++++++++++++++++++++-----
 drivers/gpu/drm/i915/i915_drv.h |  1 +
 drivers/gpu/drm/i915/intel_pm.c |  2 +-
 3 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 86bc2e685522..2273664166bc 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -1141,21 +1141,47 @@ skl_dram_get_channel_info(struct dram_channel_info *ch, u32 val)
 	return 0;
 }
 
+static bool
+intel_is_dram_ipc_capable(struct drm_i915_private *dev_priv,
+			  u32 val_ch0, u32 val_ch1,
+			  struct dram_channel_info *ch0)
+{
+	/* Display WA #1141: SKL:all KBL:all CNL:A CNL:B */
+	if (INTEL_GEN(dev_priv) > 9 &&
+	    !IS_CNL_REVID(dev_priv, CNL_REVID_A0, CNL_REVID_B0))
+		return true;
+
+	if (!IS_KABYLAKE(dev_priv) && !IS_SKYLAKE(dev_priv))
+		return true;
+
+	if (val_ch0 != val_ch1)
+		return false;
+
+	if (ch0->s_info.size == 0)
+		return true;
+	if (ch0->l_info.size == ch0->s_info.size &&
+	    ch0->l_info.width == ch0->s_info.width &&
+	    ch0->l_info.rank == ch0->s_info.rank)
+		return true;
+
+	return false;
+}
+
 static int
 skl_dram_get_channels_info(struct drm_i915_private *dev_priv)
 {
 	struct dram_info *dram_info = &dev_priv->dram_info;
 	struct dram_channel_info ch0, ch1;
-	u32 val;
+	u32 val_ch0, val_ch1;
 	int ret;
 
-	val = I915_READ(SKL_MAD_DIMM_CH0_0_0_0_MCHBAR_MCMAIN);
-	ret = skl_dram_get_channel_info(&ch0, val);
+	val_ch0 = I915_READ(SKL_MAD_DIMM_CH0_0_0_0_MCHBAR_MCMAIN);
+	ret = skl_dram_get_channel_info(&ch0, val_ch0);
 	if (ret == 0)
 		dram_info->num_channels++;
 
-	val = I915_READ(SKL_MAD_DIMM_CH1_0_0_0_MCHBAR_MCMAIN);
-	ret = skl_dram_get_channel_info(&ch1, val);
+	val_ch1 = I915_READ(SKL_MAD_DIMM_CH1_0_0_0_MCHBAR_MCMAIN);
+	ret = skl_dram_get_channel_info(&ch1, val_ch1);
 	if (ret == 0)
 		dram_info->num_channels++;
 
@@ -1185,6 +1211,13 @@ skl_dram_get_channels_info(struct drm_i915_private *dev_priv)
 	if (ch0.is_16gb_dimm || ch1.is_16gb_dimm)
 		dram_info->is_16gb_dimm = true;
 
+	if (intel_is_dram_ipc_capable(dev_priv, val_ch0, val_ch1, &ch0))
+		dev_priv->ipc_capable_mem = true;
+	else
+		dev_priv->ipc_capable_mem = false;
+
+	DRM_DEBUG_KMS("memory configuration is %sIPC capable\n",
+		      dev_priv->ipc_capable_mem ? "" : "not ");
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 854f3c828e01..036d6554c017 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2112,6 +2112,7 @@ struct drm_i915_private {
 	bool chv_phy_assert[2];
 
 	bool ipc_enabled;
+	bool ipc_capable_mem;
 
 	/* Used to save the pipe-to-encoder mapping for audio */
 	struct intel_encoder *av_enc_map[I915_MAX_PIPES];
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 2446f53adf21..39e400d5f555 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -6097,7 +6097,7 @@ void intel_enable_ipc(struct drm_i915_private *dev_priv)
 	u32 val;
 
 	/* Display WA #0477 WaDisableIPC: skl */
-	if (IS_SKYLAKE(dev_priv)) {
+	if (IS_SKYLAKE(dev_priv) || !dev_priv->ipc_capable_mem) {
 		dev_priv->ipc_enabled = false;
 		return;
 	}
-- 
2.16.2

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