drm/i915/selftests: Add tiled blits selftest

Extend coverage of the blitter client by exercising conversion to and
from tiled sources. In the process we perform spot checks to verify that
the tiling/detiling is being applied correctly, along with position
invariance of the tiling parameters.
Signed-off-by: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200430064957.14942-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_reg.h

@@ -561,6 +561,8 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
  * Registers used only by the command parser
  */
 #define BCS_SWCTRL _MMIO(0x22200)
+#define   BCS_SRC_Y REG_BIT(0)
+#define   BCS_DST_Y REG_BIT(1)
 
 /* There are 16 GPR registers */
 #define BCS_GPR(n)	_MMIO(0x22600 + (n) * 8)