Erratum SKL075: Display Flicker May Occur When Both VT-d And FBC Are Enabled
"Display flickering may occur when both FBC (Frame Buffer Compression)
and VT - d (Intel® Virtualization Technology for Directed I/O) are enabled
and in use by the display controller."
Ville found the w/a name in the database:
WaFbcTurnOffFbcWhenHyperVisorIsUsed:skl,bxt and also dug out that it
affects Broxton.
v2: Log when the quirk is applied.
v3: Ensure i915.enable_fbc is false when !HAS_FBC()
v4: Fix function name after rebase
v5: Add Broxton to the workaround
Note for backporting to stable, we need to add
((struct intel_device_info *)INTEL_INFO(ptr))
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/gpu/drm/i915/intel_fbc.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
index 8147eb9e8475..d4be07615aa9 100644
--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -1229,12 +1229,29 @@ static int intel_sanitize_fbc_option(struct drm_i915_private *dev_priv)
if (i915.enable_fbc >= 0)
return !!i915.enable_fbc;
+ if (!HAS_FBC(dev_priv))
+ return 0;
+
if (IS_BROADWELL(dev_priv))
return 1;
return 0;
}
+static bool need_fbc_vtd_wa(struct drm_i915_private *dev_priv)
+{
+#ifdef CONFIG_INTEL_IOMMU
+ /* WaFbcTurnOffFbcWhenHyperVisorIsUsed:skl,bxt */
+ if (intel_iommu_gfx_mapped &&
+ (IS_SKYLAKE(dev_priv) || IS_BROXTON(dev_priv))) {
+ DRM_INFO("Disabling framebuffer compression (FBC) to prevent screen flicker with VT-d enabled\n");
+ return true;
+ }
+#endif
+
+ return false;
+}
+
/**
* intel_fbc_init - Initialize FBC
* @dev_priv: the i915 device
@@ -1252,6 +1269,9 @@ void intel_fbc_init(struct drm_i915_private *dev_priv)
fbc->active = false;
fbc->work.scheduled = false;
+ if (need_fbc_vtd_wa(dev_priv))
+ mkwrite_device_info(dev_priv)->has_fbc = false;
+
i915.enable_fbc = intel_sanitize_fbc_option(dev_priv);
DRM_DEBUG_KMS("Sanitized enable_fbc value: %d\n", i915.enable_fbc);
--
2.8.1
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