drm: rcar-du: Rename and document dpll_ch field

Document and re-name the 'dpll_ch' field to a more precise 'dpll_mask' for
consistency with the 'channels_mask' field defined in 'struct
rcar_du_device_info'.
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/rcar-du/rcar_du_crtc.c

@@ -248,7 +248,7 @@ static void rcar_du_crtc_set_display_timing(struct rcar_du_crtc *rcrtc)
 	u32 dsmr;
 	u32 escr;
 
-	if (rcdu->info->dpll_ch & (1 << rcrtc->index)) {
+	if (rcdu->info->dpll_mask & (1 << rcrtc->index)) {
 		unsigned long target = mode_clock;
 		struct dpll_info dpll = { 0 };
 		unsigned long extclk;

drivers/gpu/drm/rcar-du/rcar_du_drv.c

@@ -218,7 +218,7 @@ static const struct rcar_du_device_info rcar_du_r8a7795_info = {
 		},
 	},
 	.num_lvds = 1,
-	.dpll_ch =  BIT(2) | BIT(1),
+	.dpll_mask =  BIT(2) | BIT(1),
 };
 
 static const struct rcar_du_device_info rcar_du_r8a7796_info = {
@@ -247,7 +247,7 @@ static const struct rcar_du_device_info rcar_du_r8a7796_info = {
 		},
 	},
 	.num_lvds = 1,
-	.dpll_ch =  BIT(1),
+	.dpll_mask =  BIT(1),
 };
 
 static const struct rcar_du_device_info rcar_du_r8a77965_info = {
@@ -276,7 +276,7 @@ static const struct rcar_du_device_info rcar_du_r8a77965_info = {
 		},
 	},
 	.num_lvds = 1,
-	.dpll_ch =  BIT(1),
+	.dpll_mask =  BIT(1),
 };
 
 static const struct rcar_du_device_info rcar_du_r8a77970_info = {

drivers/gpu/drm/rcar-du/rcar_du_drv.h

@@ -52,6 +52,7 @@ struct rcar_du_output_routing {
  * @channels_mask: bit mask of available DU channels
  * @routes: array of CRTC to output routes, indexed by output (RCAR_DU_OUTPUT_*)
  * @num_lvds: number of internal LVDS encoders
+ * @dpll_mask: bit mask of DU channels equipped with a DPLL
  */
 struct rcar_du_device_info {
 	unsigned int gen;
@@ -60,7 +61,7 @@ struct rcar_du_device_info {
 	unsigned int channels_mask;
 	struct rcar_du_output_routing routes[RCAR_DU_OUTPUT_MAX];
 	unsigned int num_lvds;
-	unsigned int dpll_ch;
+	unsigned int dpll_mask;
 };
 
 #define RCAR_DU_MAX_CRTCS		4