drm: rcar-du: Fix crash when using LVDS1 clock for CRTC

On D3 and E3 platforms, the LVDS encoder includes a PLL that can
generate a clock for the corresponding CRTC, used even when the CRTC
output to a non-LVDS port. This mechanism is supported by the driver,
but the implementation is broken in dual-link LVDS mode. In that case,
the LVDS1 drm_encoder is skipped, which causes a crash when trying to
access its bridge later on.

Fix this by storing bridge pointers internally instead of retrieving
them from the encoder. The rcar_du_device encoders field isn't used
anymore and can be dropped.

Fixes: 8e8fddab ("drm: rcar-du: Skip LVDS1 output on Gen3 when using dual-link LVDS mode")
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

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

@@ -730,13 +730,10 @@ static void rcar_du_crtc_atomic_enable(struct drm_crtc *crtc,
 	 */
 	if (rcdu->info->lvds_clk_mask & BIT(rcrtc->index) &&
 	    rstate->outputs == BIT(RCAR_DU_OUTPUT_DPAD0)) {
-		struct rcar_du_encoder *encoder =
-			rcdu->encoders[RCAR_DU_OUTPUT_LVDS0 + rcrtc->index];
+		struct drm_bridge *bridge = rcdu->lvds[rcrtc->index];
 		const struct drm_display_mode *mode =
 			&crtc->state->adjusted_mode;
-		struct drm_bridge *bridge;
 
-		bridge = drm_bridge_chain_get_first_bridge(&encoder->base);
 		rcar_lvds_clk_enable(bridge, mode->clock * 1000);
 	}
 
@@ -764,15 +761,12 @@ static void rcar_du_crtc_atomic_disable(struct drm_crtc *crtc,
 
 	if (rcdu->info->lvds_clk_mask & BIT(rcrtc->index) &&
 	    rstate->outputs == BIT(RCAR_DU_OUTPUT_DPAD0)) {
-		struct rcar_du_encoder *encoder =
-			rcdu->encoders[RCAR_DU_OUTPUT_LVDS0 + rcrtc->index];
-		struct drm_bridge *bridge;
+		struct drm_bridge *bridge = rcdu->lvds[rcrtc->index];
 
 		/*
 		 * Disable the LVDS clock output, see
 		 * rcar_du_crtc_atomic_enable().
 		 */
-		bridge = drm_bridge_chain_get_first_bridge(&encoder->base);
 		rcar_lvds_clk_disable(bridge);
 	}
 

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

@@ -20,10 +20,10 @@
 
 struct clk;
 struct device;
+struct drm_bridge;
 struct drm_device;
 struct drm_property;
 struct rcar_du_device;
-struct rcar_du_encoder;
 
 #define RCAR_DU_FEATURE_CRTC_IRQ_CLOCK	BIT(0)	/* Per-CRTC IRQ and clock */
 #define RCAR_DU_FEATURE_VSP1_SOURCE	BIT(1)	/* Has inputs from VSP1 */
@@ -71,6 +71,7 @@ struct rcar_du_device_info {
 #define RCAR_DU_MAX_CRTCS		4
 #define RCAR_DU_MAX_GROUPS		DIV_ROUND_UP(RCAR_DU_MAX_CRTCS, 2)
 #define RCAR_DU_MAX_VSPS		4
+#define RCAR_DU_MAX_LVDS		2
 
 struct rcar_du_device {
 	struct device *dev;
@@ -83,11 +84,10 @@ struct rcar_du_device {
 	struct rcar_du_crtc crtcs[RCAR_DU_MAX_CRTCS];
 	unsigned int num_crtcs;
 
-	struct rcar_du_encoder *encoders[RCAR_DU_OUTPUT_MAX];
-
 	struct rcar_du_group groups[RCAR_DU_MAX_GROUPS];
 	struct platform_device *cmms[RCAR_DU_MAX_CRTCS];
 	struct rcar_du_vsp vsps[RCAR_DU_MAX_VSPS];
+	struct drm_bridge *lvds[RCAR_DU_MAX_LVDS];
 
 	struct {
 		struct drm_property *colorkey;

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

@@ -57,7 +57,6 @@ int rcar_du_encoder_init(struct rcar_du_device *rcdu,
 	if (renc == NULL)
 		return -ENOMEM;
 
-	rcdu->encoders[output] = renc;
 	renc->output = output;
 	encoder = rcar_encoder_to_drm_encoder(renc);
 
@@ -91,6 +90,10 @@ int rcar_du_encoder_init(struct rcar_du_device *rcdu,
 			ret = -EPROBE_DEFER;
 			goto done;
 		}
+
+		if (output == RCAR_DU_OUTPUT_LVDS0 ||
+		    output == RCAR_DU_OUTPUT_LVDS1)
+			rcdu->lvds[output - RCAR_DU_OUTPUT_LVDS0] = bridge;
 	}
 
 	/*