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On LNL without a mmio read before a GGTT invalidate the GuC can incorrectly read the GGTT scratch page upon next access leading to jobs not getting scheduled. A mmio read before a GGTT invalidate seems to fix this. Since a GGTT invalidate is not a hot code path, blindly do a mmio read before each GGTT invalidate. Cc: John Harrison <John.C.Harrison@Intel.com> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> Cc: Lucas De Marchi <lucas.demarchi@intel.com> Cc: stable@vger.kernel.org Fixes:dd08ebf6c3("drm/xe: Introduce a new DRM driver for Intel GPUs") Reported-by: Paulo Zanoni <paulo.r.zanoni@intel.com> Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/3164 Signed-off-by: Matthew Brost <matthew.brost@intel.com> Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20241023221200.1797832-1-matthew.brost@intel.com Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com> (cherry picked from commit5a71019688) [ Fix conflict with mmio vs gt argument ] Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>