From 36dbc4d76918d7557b686f807106dcc799174b12 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 4 Aug 2016 08:43:53 +0100 Subject: [PATCH] drm/i915/fbc: FBC causes display flicker when VT-d is enabled on Skylake MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Cc: Paulo Zanoni Cc: Ville Syrjälä Reviewed-by: Ville Syrjälä Cc: stable@vger.kernel.org Link: http://patchwork.freedesktop.org/patch/msgid/1470296633-20388-1-git-send-email-chris@chris-wilson.co.uk --- 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); -- 2.20.1