drm: rcar-du: Fix DSI enable & disable sequence

The rcar crtc depends on the clock provided from the rcar DSI bridge.
When the DSI bridge is disabled, the clock is stopped, which causes the
crtc disable to timeout.

Also, while I have no issue with the enable, the documentation suggests
to enable the DSI before the crtc so that the crtc has its clock enabled
at enable time. This is also not done by the current driver.

To fix this, we need to keep the DSI bridge enabled until the crtc has
disabled itself, and enable the DSI bridge before crtc enables itself.

Add functions rcar_mipi_dsi_pclk_enable and rcar_mipi_dsi_pclk_disable
to the rcar DSI bridge driver which the rcar driver can use to
enable/disable the DSI clock when needed.  This is similar to what is
already done with the rcar LVDS bridge.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@ideasonboard.com>
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

@@ -29,6 +29,7 @@
 #include "rcar_du_regs.h"
 #include "rcar_du_vsp.h"
 #include "rcar_lvds.h"
+#include "rcar_mipi_dsi.h"
 
 static u32 rcar_du_crtc_read(struct rcar_du_crtc *rcrtc, u32 reg)
 {
@@ -747,6 +748,18 @@ static void rcar_du_crtc_atomic_enable(struct drm_crtc *crtc,
 		rcar_lvds_pclk_enable(bridge, mode->clock * 1000);
 	}
 
+	/*
+	 * Similarly to LVDS, on V3U the dot clock is provided by the DSI
+	 * encoder, and we need to enable the DSI clocks before enabling the CRTC.
+	 */
+	if ((rcdu->info->dsi_clk_mask & BIT(rcrtc->index)) &&
+	    (rstate->outputs &
+	     (BIT(RCAR_DU_OUTPUT_DSI0) | BIT(RCAR_DU_OUTPUT_DSI1)))) {
+		struct drm_bridge *bridge = rcdu->dsi[rcrtc->index];
+
+		rcar_mipi_dsi_pclk_enable(bridge, state);
+	}
+
 	rcar_du_crtc_start(rcrtc);
 
 	/*
@@ -780,6 +793,19 @@ static void rcar_du_crtc_atomic_disable(struct drm_crtc *crtc,
 		rcar_lvds_pclk_disable(bridge);
 	}
 
+	if ((rcdu->info->dsi_clk_mask & BIT(rcrtc->index)) &&
+	    (rstate->outputs &
+	     (BIT(RCAR_DU_OUTPUT_DSI0) | BIT(RCAR_DU_OUTPUT_DSI1)))) {
+		struct drm_bridge *bridge = rcdu->dsi[rcrtc->index];
+
+		/*
+		 * Disable the DSI clock output, see
+		 * rcar_du_crtc_atomic_enable().
+		 */
+
+		rcar_mipi_dsi_pclk_disable(bridge);
+	}
+
 	spin_lock_irq(&crtc->dev->event_lock);
 	if (crtc->state->event) {
 		drm_crtc_send_vblank_event(crtc, crtc->state->event);

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

@@ -92,6 +92,7 @@ struct rcar_du_device_info {
 #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
+#define RCAR_DU_MAX_DSI			2
 
 struct rcar_du_device {
 	struct device *dev;
@@ -108,6 +109,7 @@ struct rcar_du_device {
 	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 drm_bridge *dsi[RCAR_DU_MAX_DSI];
 
 	struct {
 		struct drm_property *colorkey;

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

@@ -79,6 +79,10 @@ int rcar_du_encoder_init(struct rcar_du_device *rcdu,
 		if (output == RCAR_DU_OUTPUT_LVDS0 ||
 		    output == RCAR_DU_OUTPUT_LVDS1)
 			rcdu->lvds[output - RCAR_DU_OUTPUT_LVDS0] = bridge;
+
+		if (output == RCAR_DU_OUTPUT_DSI0 ||
+		    output == RCAR_DU_OUTPUT_DSI1)
+			rcdu->dsi[output - RCAR_DU_OUTPUT_DSI0] = bridge;
 	}
 
 	/*

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

@@ -25,6 +25,7 @@
 #include <drm/drm_panel.h>
 #include <drm/drm_probe_helper.h>
 
+#include "rcar_mipi_dsi.h"
 #include "rcar_mipi_dsi_regs.h"
 
 struct rcar_mipi_dsi {
@@ -598,7 +599,22 @@ static int rcar_mipi_dsi_attach(struct drm_bridge *bridge,
 static void rcar_mipi_dsi_atomic_enable(struct drm_bridge *bridge,
 					struct drm_bridge_state *old_bridge_state)
 {
-	struct drm_atomic_state *state = old_bridge_state->base.state;
+	struct rcar_mipi_dsi *dsi = bridge_to_rcar_mipi_dsi(bridge);
+
+	rcar_mipi_dsi_start_video(dsi);
+}
+
+static void rcar_mipi_dsi_atomic_disable(struct drm_bridge *bridge,
+					 struct drm_bridge_state *old_bridge_state)
+{
+	struct rcar_mipi_dsi *dsi = bridge_to_rcar_mipi_dsi(bridge);
+
+	rcar_mipi_dsi_stop_video(dsi);
+}
+
+void rcar_mipi_dsi_pclk_enable(struct drm_bridge *bridge,
+			       struct drm_atomic_state *state)
+{
 	struct rcar_mipi_dsi *dsi = bridge_to_rcar_mipi_dsi(bridge);
 	const struct drm_display_mode *mode;
 	struct drm_connector *connector;
@@ -626,8 +642,6 @@ static void rcar_mipi_dsi_atomic_enable(struct drm_bridge *bridge,
 	if (ret < 0)
 		goto err_dsi_start_hs;
 
-	rcar_mipi_dsi_start_video(dsi);
-
 	return;
 
 err_dsi_start_hs:
@@ -635,16 +649,16 @@ static void rcar_mipi_dsi_atomic_enable(struct drm_bridge *bridge,
 err_dsi_startup:
 	rcar_mipi_dsi_clk_disable(dsi);
 }
+EXPORT_SYMBOL_GPL(rcar_mipi_dsi_pclk_enable);
 
-static void rcar_mipi_dsi_atomic_disable(struct drm_bridge *bridge,
-					 struct drm_bridge_state *old_bridge_state)
+void rcar_mipi_dsi_pclk_disable(struct drm_bridge *bridge)
 {
 	struct rcar_mipi_dsi *dsi = bridge_to_rcar_mipi_dsi(bridge);
 
-	rcar_mipi_dsi_stop_video(dsi);
 	rcar_mipi_dsi_shutdown(dsi);
 	rcar_mipi_dsi_clk_disable(dsi);
 }
+EXPORT_SYMBOL_GPL(rcar_mipi_dsi_pclk_disable);
 
 static enum drm_mode_status
 rcar_mipi_dsi_bridge_mode_valid(struct drm_bridge *bridge,

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

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * R-Car DSI Encoder
+ *
+ * Copyright (C) 2022 Renesas Electronics Corporation
+ *
+ * Contact: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
+ */
+
+#ifndef __RCAR_MIPI_DSI_H__
+#define __RCAR_MIPI_DSI_H__
+
+struct drm_atomic_state;
+struct drm_bridge;
+
+#if IS_ENABLED(CONFIG_DRM_RCAR_MIPI_DSI)
+void rcar_mipi_dsi_pclk_enable(struct drm_bridge *bridge,
+			       struct drm_atomic_state *state);
+void rcar_mipi_dsi_pclk_disable(struct drm_bridge *bridge);
+#else
+static inline void rcar_mipi_dsi_pclk_enable(struct drm_bridge *bridge,
+					     struct drm_atomic_state *state)
+{
+}
+
+static inline void rcar_mipi_dsi_pclk_disable(struct drm_bridge *bridge)
+{
+}
+#endif /* CONFIG_DRM_RCAR_MIPI_DSI */
+
+#endif /* __RCAR_MIPI_DSI_H__ */