drm/i915/dg1: Update comp master/slave relationships for PHYs

As with RKL, DG1's PHY C acts as a comp master for PHY D.

Bspec: 49291
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201007002210.3678024-7-lucas.demarchi@intel.com

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

@@ -243,14 +243,14 @@ static bool phy_is_master(struct drm_i915_private *dev_priv, enum phy phy)
 	 *
 	 * ICL,TGL:
 	 *   A(master) -> B(slave), C(slave)
-	 * RKL:
+	 * RKL,DG1:
 	 *   A(master) -> B(slave)
 	 *   C(master) -> D(slave)
 	 *
 	 * We must set the IREFGEN bit for any PHY acting as a master
 	 * to another PHY.
 	 */
-	if (IS_ROCKETLAKE(dev_priv) && phy == PHY_C)
+	if ((IS_DG1(dev_priv) || IS_ROCKETLAKE(dev_priv)) && phy == PHY_C)
 		return true;
 
 	return phy == PHY_A;