drm/i915/display: Add gamma precision function for CHV

intel_color_get_gamma_bit_precision() is extended for
cherryview by adding chv_gamma_precision(), i965 will use existing
i9xx_gamma_precision() func only.
Signed-off-by: Swati Sharma <swati2.sharma@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1568030503-26747-2-git-send-email-swati2.sharma@intel.com

drivers/gpu/drm/i915/display/intel_color.c

@@ -1400,6 +1400,14 @@ static int ilk_gamma_precision(const struct intel_crtc_state *crtc_state)
 	}
 }
 
+static int chv_gamma_precision(const struct intel_crtc_state *crtc_state)
+{
+	if (crtc_state->cgm_mode & CGM_PIPE_MODE_GAMMA)
+		return 10;
+	else
+		return i9xx_gamma_precision(crtc_state);
+}
+
 static int glk_gamma_precision(const struct intel_crtc_state *crtc_state)
 {
 	switch (crtc_state->gamma_mode) {
@@ -1421,12 +1429,17 @@ int intel_color_get_gamma_bit_precision(const struct intel_crtc_state *crtc_stat
 	if (!crtc_state->gamma_enable)
 		return 0;
 
-	if (HAS_GMCH(dev_priv) && !IS_CHERRYVIEW(dev_priv))
+	if (HAS_GMCH(dev_priv)) {
+		if (IS_CHERRYVIEW(dev_priv))
+			return chv_gamma_precision(crtc_state);
+		else
 			return i9xx_gamma_precision(crtc_state);
-	else if (IS_CANNONLAKE(dev_priv) || IS_GEMINILAKE(dev_priv))
+	} else {
+		if (IS_CANNONLAKE(dev_priv) || IS_GEMINILAKE(dev_priv))
 			return glk_gamma_precision(crtc_state);
 		else if (IS_IRONLAKE(dev_priv))
 			return ilk_gamma_precision(crtc_state);
+	}
 
 	return 0;
 }