drm/i915: Add the predicate source registers to the register whitelist

The predicate source registers are needed to implement conditional
rendering without stalling. The two source registers are used to load
the previous values of the PS_DEPTH_COUNT register saved from
PIPE_CONTROL commands. These can then be compared and used to set the
predicate enable bit via the MI_PREDICATE command.

The command parser version number is increased to 2 to make it easier
to detect the new functionality in user space.

Signed-off-by: Neil Roberts <neil@linux.intel.com>
Reviewed-by: Brad Volkin <bradley.d.volkin@intel.com> (v1)
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org> (v1)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_cmd_parser.c

@@ -413,6 +413,8 @@ static const u32 gen7_render_regs[] = {
 	REG64(PS_INVOCATION_COUNT),
 	REG64(PS_DEPTH_COUNT),
 	OACONTROL, /* Only allowed for LRI and SRM. See below. */
+	REG64(MI_PREDICATE_SRC0),
+	REG64(MI_PREDICATE_SRC1),
 	GEN7_3DPRIM_END_OFFSET,
 	GEN7_3DPRIM_START_VERTEX,
 	GEN7_3DPRIM_VERTEX_COUNT,
@@ -1072,6 +1074,8 @@ int i915_cmd_parser_get_version(void)
 	 *
 	 * 1. Initial version. Checks batches and reports violations, but leaves
 	 *    hardware parsing enabled (so does not allow new use cases).
+	 * 2. Allow access to the MI_PREDICATE_SRC0 and
+	 *    MI_PREDICATE_SRC1 registers.
 	 */
-	return 1;
+	return 2;
 }

drivers/gpu/drm/i915/i915_reg.h

@@ -314,6 +314,8 @@
 #define   MI_BATCH_GTT		    (2<<6) /* aliased with (1<<7) on gen4 */
 #define MI_BATCH_BUFFER_START_GEN8	MI_INSTR(0x31, 1)
 
+#define MI_PREDICATE_SRC0	(0x2400)
+#define MI_PREDICATE_SRC1	(0x2408)
 
 #define MI_PREDICATE_RESULT_2	(0x2214)
 #define  LOWER_SLICE_ENABLED	(1<<0)