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Commit 6ba0566c authored by Paulo Zanoni's avatar Paulo Zanoni Committed by Jani Nikula
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drm/i915: skip the first 4k of stolen memory on everything >= gen8 

BSpec got updated and this workaround is now listed as standard
required programming for all subsequent projects. This is confirmed to
fix Skylake screen flickering issues (probably caused by the fact that
we initialized a ring in the first page of stolen, but I didn't 100%
confirm this theory).

v2: this is the patch that fixes the screen flickering, document it.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94605


Cc: stable@vger.kernel.org
Tested-by: default avatarDominik Klementowski <dominik232@gmail.com>
Signed-off-by: default avatarPaulo Zanoni <paulo.r.zanoni@intel.com>
Acked-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1481727338-9901-1-git-send-email-paulo.r.zanoni@intel.com


(cherry picked from commit d4353761)
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
parent abb0deac

drivers/gpu/drm/i915/i915_gem_stolen.c

+2 −3
Original line number Diff line number Diff line
@@ -55,10 +55,9 @@ int i915_gem_stolen_insert_node_in_range(struct drm_i915_private *dev_priv, 
		return -ENODEV;



	/* See the comment at the drm_mm_init() call for more about this check.

	 * WaSkipStolenMemoryFirstPage:bdw,chv,kbl (incomplete)

	 * WaSkipStolenMemoryFirstPage:bdw+ (incomplete)

	 */

	if (start < 4096 && (IS_GEN8(dev_priv) ||

			     IS_KBL_REVID(dev_priv, 0, KBL_REVID_A0)))

	if (start < 4096 && INTEL_GEN(dev_priv) >= 8)

		start = 4096;



	mutex_lock(&dev_priv->mm.stolen_lock);