drm/i915/mtl: Disable stolen memory backed FB for A0

Stolen memory is not usable for MTL A0 stepping beyond
certain access size and we have no control over userspace
access size of /dev/fb which can be backed by stolen memory.
So disable stolen memory backed fb by setting i915->dsm.usable_size
to zero.

v2: remove hsdes reference and fix commit message(Andi)
v3: use revid as we want to target SOC stepping(Radhakrishna)

Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230404181342.23362-1-nirmoy.das@intel.com

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
index 8ac376c24aa22cde9a7f55d212a1303f711c1582..ee492d823f1bb8440fed60c69fd2b368ae60a966 100644 (file)
--- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
@@ -535,6 +535,14 @@ static int i915_gem_init_stolen(struct intel_memory_region *mem)
        /* Basic memrange allocator for stolen space. */
        drm_mm_init(&i915->mm.stolen, 0, i915->dsm.usable_size);
 
+       /*
+        * Access to stolen lmem beyond certain size for MTL A0 stepping
+        * would crash the machine. Disable stolen lmem for userspace access
+        * by setting usable_size to zero.
+        */
+       if (IS_METEORLAKE(i915) && INTEL_REVID(i915) == 0x0)
+               i915->dsm.usable_size = 0;
+
        return 0;
 }