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drm/i915/fbc: FBC causes display flicker when VT-d is enabled on Skylake

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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
  #define mkwrite_device_info(ptr) \
	((struct intel_device_info *)INTEL_INFO(ptr))

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: stable@vger.kernel.org
Link: http://patchwork.freedesktop.org/patch/msgid/1470296633-20388-1-git-send-email-chris@chris-wilson.co.uk
(cherry picked from commit 36dbc4d769)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
This commit is contained in:
Chris Wilson 2016-08-04 08:43:53 +01:00 committed by Jani Nikula
parent d8b6161f72
commit 0a491b96aa
1 changed files with 20 additions and 0 deletions
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20
drivers/gpu/drm/i915/intel_fbc.c
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@ -1230,12 +1230,29 @@ 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
@ -1253,6 +1270,9 @@ 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);