drm/i915: Change DCC tiling detection case to cover only mobile parts.

Later spec investigation has revealed that every 9xx mobile part has
had this register in this format.  Also, no non-mobile parts have been shown
to have this register.  So make all mobile use the same code, and all
non-mobile use the hack 965 detection.
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/i915_gem_tiling.c

@@ -96,16 +96,16 @@ i915_gem_detect_bit_6_swizzle(struct drm_device *dev)
 		 */
 		swizzle_x = I915_BIT_6_SWIZZLE_NONE;
 		swizzle_y = I915_BIT_6_SWIZZLE_NONE;
-	} else if ((!IS_I965G(dev) && !IS_G33(dev)) || IS_I965GM(dev) ||
-		   IS_GM45(dev)) {
+	} else if (IS_MOBILE(dev)) {
 		uint32_t dcc;
 
-		/* On 915-945 and GM965, channel interleave by the CPU is
-		 * determined by DCC.  The CPU will alternate based on bit 6
-		 * in interleaved mode, and the GPU will then also alternate
-		 * on bit 6, 9, and 10 for X, but the CPU may also optionally
-		 * alternate based on bit 17 (XOR not disabled and XOR
-		 * bit == 17).
+		/* On mobile 9xx chipsets, channel interleave by the CPU is
+		 * determined by DCC.  For single-channel, neither the CPU
+		 * nor the GPU do swizzling.  For dual channel interleaved,
+		 * the GPU's interleave is bit 9 and 10 for X tiled, and bit
+		 * 9 for Y tiled.  The CPU's interleave is independent, and
+		 * can be based on either bit 11 (haven't seen this yet) or
+		 * bit 17 (common).
 		 */
 		dcc = I915_READ(DCC);
 		switch (dcc & DCC_ADDRESSING_MODE_MASK) {
@@ -115,19 +115,18 @@ i915_gem_detect_bit_6_swizzle(struct drm_device *dev)
 			swizzle_y = I915_BIT_6_SWIZZLE_NONE;
 			break;
 		case DCC_ADDRESSING_MODE_DUAL_CHANNEL_INTERLEAVED:
-			if (IS_I915G(dev) || IS_I915GM(dev) ||
-			    dcc & DCC_CHANNEL_XOR_DISABLE) {
+			if (dcc & DCC_CHANNEL_XOR_DISABLE) {
+				/* This is the base swizzling by the GPU for
+				 * tiled buffers.
+				 */
 				swizzle_x = I915_BIT_6_SWIZZLE_9_10;
 				swizzle_y = I915_BIT_6_SWIZZLE_9;
-			} else if ((IS_I965GM(dev) || IS_GM45(dev)) &&
-				   (dcc & DCC_CHANNEL_XOR_BIT_17) == 0) {
-				/* GM965/GM45 does either bit 11 or bit 17
-				 * swizzling.
-				 */
+			} else if ((dcc & DCC_CHANNEL_XOR_BIT_17) == 0) {
+				/* Bit 11 swizzling by the CPU in addition. */
 				swizzle_x = I915_BIT_6_SWIZZLE_9_10_11;
 				swizzle_y = I915_BIT_6_SWIZZLE_9_11;
 			} else {
-				/* Bit 17 or perhaps other swizzling */
+				/* Bit 17 swizzling by the CPU in addition. */
 				swizzle_x = I915_BIT_6_SWIZZLE_UNKNOWN;
 				swizzle_y = I915_BIT_6_SWIZZLE_UNKNOWN;
 			}