drm/i915: Disable mmap ioctl for gen12+

The platform should exclusively use mmap_offset, one less path to worry
about for discrete.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210601074654.3103-14-thomas.hellstrom@linux.intel.com

drivers/gpu/drm/i915/gem/i915_gem_mman.c

@@ -56,10 +56,17 @@ int
 i915_gem_mmap_ioctl(struct drm_device *dev, void *data,
 		    struct drm_file *file)
 {
+	struct drm_i915_private *i915 = to_i915(dev);
 	struct drm_i915_gem_mmap *args = data;
 	struct drm_i915_gem_object *obj;
 	unsigned long addr;
 
+	/* mmap ioctl is disallowed for all platforms after TGL-LP.  This also
+	 * covers all platforms with local memory.
+	 */
+	if (INTEL_GEN(i915) >= 12 && !IS_TIGERLAKE(i915))
+		return -EOPNOTSUPP;
+
 	if (args->flags & ~(I915_MMAP_WC))
 		return -EINVAL;