drm/i915: Report the actual swizzling back to userspace

Userspace cares about whether or not swizzling depends on the page
address for its direct access into bound objects. Extend the get_tiling
ioctl to report the physical swizzling value in addition to the logical
swizzling value so that userspace can accurately determine when it is
possible for manual detiling.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Akash Goel <akash.goel@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Testcase: igt/gem_tiled_wc
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_tiling.c

@@ -458,6 +458,7 @@ i915_gem_get_tiling(struct drm_device *dev, void *data,
 	}
 
 	/* Hide bit 17 from the user -- see comment in i915_gem_set_tiling */
+	args->phys_swizzle_mode = args->swizzle_mode;
 	if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_17)
 		args->swizzle_mode = I915_BIT_6_SWIZZLE_9;
 	if (args->swizzle_mode == I915_BIT_6_SWIZZLE_9_10_17)

include/uapi/drm/i915_drm.h

@@ -876,6 +876,12 @@ struct drm_i915_gem_get_tiling {
 	 * mmap mapping.
 	 */
 	__u32 swizzle_mode;
+
+	/**
+	 * Returned address bit 6 swizzling required for CPU access through
+	 * mmap mapping whilst bound.
+	 */
+	__u32 phys_swizzle_mode;
 };
 
 struct drm_i915_gem_get_aperture {