drm/i915/icl: Fix CRC mismatch error for DP link layer compliance

Setting the pixel rounding bit to 1 in PIPE_CHICKEN register allows
to passthrough FB pixels unmodified across pipe. This fixes the failures
for DP link layer compliance tests 4.4.1.1, 4.4.1.2 & 4.4.1.3.
(Lineage #1605353570)

v2: This is also needed to fix failing IGT test case kms_cursor_crc on
ICL.(Mika Kahola)
Make macros consistent with i915_reg.h comments.(Jani Nikula)

Cc: Clint Taylor <[e-mail]>
Cc: Mika Kahola <[e-mail]>
Cc: Jani Nikula <[e-mail]>
Signed-off-by: Aditya Swarup <[e-mail]>
Reviewed-by: Mika Kahola <[e-mail]>
Signed-off-by: Maarten Lankhorst <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
References: https://bugs.freedesktop.org/show_bug.cgi?id=103232

drivers/gpu/drm/i915/i915_reg.h

···
 #define  GEN9_LBS_SLA_RETRY_TIMER_DECREMENT_ENABLE	(1 << 2)
 
 /*GEN11 chicken */
-#define _PIPEA_CHICKEN			0x70038
-#define _PIPEB_CHICKEN			0x71038
-#define _PIPEC_CHICKEN			0x72038
-#define  PER_PIXEL_ALPHA_BYPASS_EN	(1 << 7)
-#define PIPE_CHICKEN(pipe)		_MMIO_PIPE(pipe, _PIPEA_CHICKEN,\
-						   _PIPEB_CHICKEN)
+#define _PIPEA_CHICKEN				0x70038
+#define _PIPEB_CHICKEN				0x71038
+#define _PIPEC_CHICKEN				0x72038
+#define PIPE_CHICKEN(pipe)			_MMIO_PIPE(pipe, _PIPEA_CHICKEN,\
+							   _PIPEB_CHICKEN)
+#define   PIXEL_ROUNDING_TRUNC_FB_PASSTHRU 	(1 << 15)
+#define   PER_PIXEL_ALPHA_BYPASS_EN		(1 << 7)
 
 /* PCH */
 

drivers/gpu/drm/i915/intel_display.c

···
 	 * and rounding for per-pixel values 00 and 0xff
 	 */
 	tmp |= PER_PIXEL_ALPHA_BYPASS_EN;
-
+	/*
+	 * Display WA # 1605353570: icl
+	 * Set the pixel rounding bit to 1 for allowing
+	 * passthrough of Frame buffer pixels unmodified
+	 * across pipe
+	 */
+	tmp |= PIXEL_ROUNDING_TRUNC_FB_PASSTHRU;
 	I915_WRITE(PIPE_CHICKEN(pipe), tmp);
 }