[PATCH] drm/i915/gen9: Check for DC state mismatch

[Patrik Jakobsson <patrik.jakobsson@linux.intel.com>]

The DMC can incorrectly run off and allow DC states on it's own. We
don't know the root-cause for this yet but this patch makes it more
visible.

Signed-off-by: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h         | 1 +
 drivers/gpu/drm/i915/intel_csr.c        | 2 ++
 drivers/gpu/drm/i915/intel_runtime_pm.c | 8 ++++++++
 3 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index e11eef1..7e33454 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -746,6 +746,7 @@ struct intel_csr {
 	uint32_t mmio_count;
 	i915_reg_t mmioaddr[8];
 	uint32_t mmiodata[8];
+	uint32_t dc_state;
 };
 
 #define DEV_INFO_FOR_EACH_FLAG(func, sep) \
diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
index 2a7ec31..b453fcc 100644
--- a/drivers/gpu/drm/i915/intel_csr.c
+++ b/drivers/gpu/drm/i915/intel_csr.c
@@ -243,6 +243,8 @@ void intel_csr_load_program(struct drm_i915_private *dev_priv)
 		I915_WRITE(dev_priv->csr.mmioaddr[i],
 			   dev_priv->csr.mmiodata[i]);
 	}
+
+	dev_priv->csr.dc_state = 0;
 }
 
 static uint32_t *parse_csr_fw(struct drm_i915_private *dev_priv,
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index bbca527..e79674b 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -494,10 +494,18 @@ static void gen9_set_dc_state(struct drm_i915_private *dev_priv, uint32_t state)
 	val = I915_READ(DC_STATE_EN);
 	DRM_DEBUG_KMS("Setting DC state from %02x to %02x\n",
 		      val & mask, state);
+
+	/* Check if DMC is ignoring our DC state requests */
+	if ((val & mask) != dev_priv->csr.dc_state)
+		DRM_ERROR("DC state mismatch (0x%x -> 0x%x)\n",
+			  dev_priv->csr.dc_state, val & mask);
+
 	val &= ~mask;
 	val |= state;
 	I915_WRITE(DC_STATE_EN, val);
 	POSTING_READ(DC_STATE_EN);
+
+	dev_priv->csr.dc_state = val & mask;
 }
 
 void bxt_enable_dc9(struct drm_i915_private *dev_priv)
-- 
2.5.0

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