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Date:   Thu, 16 Apr 2020 20:33:26 +0300
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Enric Balletbo i Serra <enric.balletbo@collabora.com>
Cc:     linux-kernel@vger.kernel.org,
        Collabora Kernel ML <kernel@collabora.com>,
        matthias.bgg@gmail.com, drinkcat@chromium.org, hsinyi@chromium.org,
        Chun-Kuang Hu <chunkuang.hu@kernel.org>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        dri-devel@lists.freedesktop.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org
Subject: Re: [PATCH v2 6/7] drm/mediatek: mtk_dsi: Use the drm_panel_bridge
 API
Message-ID: <20200416173326.GP4796@pendragon.ideasonboard.com>
References: <20200416155720.2360443-1-enric.balletbo@collabora.com>
 <20200416155720.2360443-7-enric.balletbo@collabora.com>
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In-Reply-To: <20200416155720.2360443-7-enric.balletbo@collabora.com>
Sender: linux-kernel-owner@vger.kernel.org
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Hi Enric,

Thank you for the patch.

On Thu, Apr 16, 2020 at 05:57:18PM +0200, Enric Balletbo i Serra wrote:
> Replace the manual panel handling code by a drm_panel_bridge. This
> simplifies the driver and allows all components in the display pipeline
> to be treated as bridges, paving the way to generic connector handling.
> 
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> ---
> 
> Changes in v2:
> - Do not set connector_type for panel here. (Sam Ravnborg)
> 
>  drivers/gpu/drm/mediatek/mtk_dsi.c | 177 ++++-------------------------
>  1 file changed, 19 insertions(+), 158 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 48361c1e9f34..44718fa3d1ca 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -182,8 +182,7 @@ struct mtk_dsi {
>  	struct mipi_dsi_host host;
>  	struct drm_encoder encoder;
>  	struct drm_bridge bridge;
> -	struct drm_connector conn;
> -	struct drm_panel *panel;
> +	struct drm_bridge *panel_bridge;

I think you can use the next_bridge field to store the panel bridge, it
will simplify the code a bit in mtk_dsi_bridge_attach().

>  	struct drm_bridge *next_bridge;
>  	struct phy *phy;
>  
> @@ -212,11 +211,6 @@ static inline struct mtk_dsi *bridge_to_dsi(struct drm_bridge *b)
>  	return container_of(b, struct mtk_dsi, bridge);
>  }
>  
> -static inline struct mtk_dsi *connector_to_dsi(struct drm_connector *c)
> -{
> -	return container_of(c, struct mtk_dsi, conn);
> -}
> -
>  static inline struct mtk_dsi *host_to_dsi(struct mipi_dsi_host *h)
>  {
>  	return container_of(h, struct mtk_dsi, host);
> @@ -682,16 +676,7 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
>  	mtk_dsi_lane0_ulp_mode_leave(dsi);
>  	mtk_dsi_clk_hs_mode(dsi, 0);
>  
> -	if (dsi->panel) {
> -		if (drm_panel_prepare(dsi->panel)) {
> -			DRM_ERROR("failed to prepare the panel\n");
> -			goto err_disable_digital_clk;
> -		}
> -	}
> -
>  	return 0;
> -err_disable_digital_clk:
> -	clk_disable_unprepare(dsi->digital_clk);
>  err_disable_engine_clk:
>  	clk_disable_unprepare(dsi->engine_clk);
>  err_phy_power_off:
> @@ -718,15 +703,7 @@ static void mtk_dsi_poweroff(struct mtk_dsi *dsi)
>  	 */
>  	mtk_dsi_stop(dsi);
>  
> -	if (!mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500)) {
> -		if (dsi->panel) {
> -			if (drm_panel_unprepare(dsi->panel)) {
> -				DRM_ERROR("failed to unprepare the panel\n");
> -				return;
> -			}
> -		}
> -	}
> -
> +	mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500);
>  	mtk_dsi_reset_engine(dsi);
>  	mtk_dsi_lane0_ulp_mode_enter(dsi);
>  	mtk_dsi_clk_ulp_mode_enter(dsi);
> @@ -757,19 +734,7 @@ static void mtk_output_dsi_enable(struct mtk_dsi *dsi)
>  
>  	mtk_dsi_start(dsi);
>  
> -	if (dsi->panel) {
> -		if (drm_panel_enable(dsi->panel)) {
> -			DRM_ERROR("failed to enable the panel\n");
> -			goto err_dsi_power_off;
> -		}
> -	}
> -
>  	dsi->enabled = true;
> -
> -	return;
> -err_dsi_power_off:
> -	mtk_dsi_stop(dsi);
> -	mtk_dsi_poweroff(dsi);
>  }
>  
>  static void mtk_output_dsi_disable(struct mtk_dsi *dsi)
> @@ -777,34 +742,24 @@ static void mtk_output_dsi_disable(struct mtk_dsi *dsi)
>  	if (!dsi->enabled)
>  		return;
>  
> -	if (dsi->panel) {
> -		if (drm_panel_disable(dsi->panel)) {
> -			DRM_ERROR("failed to disable the panel\n");
> -			return;
> -		}
> -	}
> -
>  	mtk_dsi_poweroff(dsi);
>  
>  	dsi->enabled = false;
>  }
>  
> -static int mtk_dsi_create_conn_enc(struct drm_device *drm, struct mtk_dsi *dsi);
> -static void mtk_dsi_destroy_conn_enc(struct mtk_dsi *dsi);
> -
>  static int mtk_dsi_bridge_attach(struct drm_bridge *bridge,
>  				 enum drm_bridge_attach_flags flags)
>  {
>  	struct mtk_dsi *dsi = bridge_to_dsi(bridge);
> +	struct drm_bridge *next;
>  
> -	return mtk_dsi_create_conn_enc(bridge->dev, dsi);
> -}
> -
> -static void mtk_dsi_bridge_detach(struct drm_bridge *bridge)
> -{
> -	struct mtk_dsi *dsi = bridge_to_dsi(bridge);
> +	if (dsi->next_bridge)
> +		next = dsi->next_bridge;
> +	else
> +		next = dsi->panel_bridge;
>  
> -	mtk_dsi_destroy_conn_enc(dsi);
> +	/* Attach the panel or bridge to the dsi bridge */
> +	return drm_bridge_attach(bridge->encoder, next, &dsi->bridge, flags);
>  }
>  
>  static void mtk_dsi_bridge_mode_set(struct drm_bridge *bridge,
> @@ -830,101 +785,13 @@ static void mtk_dsi_bridge_enable(struct drm_bridge *bridge)
>  	mtk_output_dsi_enable(dsi);
>  }
>  
> -static int mtk_dsi_connector_get_modes(struct drm_connector *connector)
> -{
> -	struct mtk_dsi *dsi = connector_to_dsi(connector);
> -
> -	return drm_panel_get_modes(dsi->panel, connector);
> -}
> -
>  static const struct drm_bridge_funcs mtk_dsi_bridge_funcs = {
>  	.attach = mtk_dsi_bridge_attach,
> -	.detach = mtk_dsi_bridge_detach,
>  	.disable = mtk_dsi_bridge_disable,
>  	.enable = mtk_dsi_bridge_enable,
>  	.mode_set = mtk_dsi_bridge_mode_set,
>  };
>  
> -static const struct drm_connector_funcs mtk_dsi_connector_funcs = {
> -	.fill_modes = drm_helper_probe_single_connector_modes,
> -	.destroy = drm_connector_cleanup,
> -	.reset = drm_atomic_helper_connector_reset,
> -	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> -	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
> -};
> -
> -static const struct drm_connector_helper_funcs
> -	mtk_dsi_connector_helper_funcs = {
> -	.get_modes = mtk_dsi_connector_get_modes,
> -};
> -
> -static int mtk_dsi_create_connector(struct drm_device *drm, struct mtk_dsi *dsi)
> -{
> -	int ret;
> -
> -	ret = drm_connector_init(drm, &dsi->conn, &mtk_dsi_connector_funcs,
> -				 DRM_MODE_CONNECTOR_DSI);
> -	if (ret) {
> -		DRM_ERROR("Failed to connector init to drm\n");
> -		return ret;
> -	}
> -
> -	drm_connector_helper_add(&dsi->conn, &mtk_dsi_connector_helper_funcs);
> -
> -	dsi->conn.dpms = DRM_MODE_DPMS_OFF;
> -	drm_connector_attach_encoder(&dsi->conn, &dsi->encoder);
> -
> -	if (dsi->panel) {
> -		ret = drm_panel_attach(dsi->panel, &dsi->conn);
> -		if (ret) {
> -			DRM_ERROR("Failed to attach panel to drm\n");
> -			goto err_connector_cleanup;
> -		}
> -	}
> -
> -	return 0;
> -
> -err_connector_cleanup:
> -	drm_connector_cleanup(&dsi->conn);
> -	return ret;
> -}
> -
> -static int mtk_dsi_create_conn_enc(struct drm_device *drm, struct mtk_dsi *dsi)
> -{
> -	int ret;
> -
> -	/* If there's a bridge, attach to it and let it create the connector */
> -	if (dsi->next_bridge) {
> -		ret = drm_bridge_attach(&dsi->encoder, dsi->next_bridge, NULL,
> -					0);
> -		if (ret) {
> -			DRM_ERROR("Failed to attach bridge to drm\n");
> -			goto err_encoder_cleanup;
> -		}
> -	} else {
> -		/* Otherwise create our own connector and attach to a panel */
> -		ret = mtk_dsi_create_connector(drm, dsi);
> -		if (ret)
> -			goto err_encoder_cleanup;
> -	}
> -
> -	return 0;
> -
> -err_encoder_cleanup:
> -	drm_encoder_cleanup(&dsi->encoder);
> -	return ret;
> -}
> -
> -static void mtk_dsi_destroy_conn_enc(struct mtk_dsi *dsi)
> -{
> -	drm_encoder_cleanup(&dsi->encoder);
> -	/* Skip connector cleanup if creation was delegated to the bridge */
> -	if (dsi->conn.dev)
> -		drm_connector_cleanup(&dsi->conn);
> -	if (dsi->panel)
> -		drm_panel_detach(dsi->panel);
> -}
> -
>  static void mtk_dsi_ddp_start(struct mtk_ddp_comp *comp)
>  {
>  	struct mtk_dsi *dsi = container_of(comp, struct mtk_dsi, ddp_comp);
> @@ -953,20 +820,6 @@ static int mtk_dsi_host_attach(struct mipi_dsi_host *host,
>  	dsi->format = device->format;
>  	dsi->mode_flags = device->mode_flags;
>  
> -	if (dsi->conn.dev)
> -		drm_helper_hpd_irq_event(dsi->conn.dev);
> -
> -	return 0;
> -}
> -
> -static int mtk_dsi_host_detach(struct mipi_dsi_host *host,
> -			       struct mipi_dsi_device *device)
> -{
> -	struct mtk_dsi *dsi = host_to_dsi(host);
> -
> -	if (dsi->conn.dev)
> -		drm_helper_hpd_irq_event(dsi->conn.dev);
> -
>  	return 0;
>  }
>  
> @@ -1110,7 +963,6 @@ static ssize_t mtk_dsi_host_transfer(struct mipi_dsi_host *host,
>  
>  static const struct mipi_dsi_host_ops mtk_dsi_ops = {
>  	.attach = mtk_dsi_host_attach,
> -	.detach = mtk_dsi_host_detach,
>  	.transfer = mtk_dsi_host_transfer,
>  };
>  
> @@ -1184,6 +1036,7 @@ static int mtk_dsi_probe(struct platform_device *pdev)
>  {
>  	struct mtk_dsi *dsi;
>  	struct device *dev = &pdev->dev;
> +	struct drm_panel *panel;
>  	struct resource *regs;
>  	int irq_num;
>  	int comp_id;
> @@ -1202,10 +1055,18 @@ static int mtk_dsi_probe(struct platform_device *pdev)
>  	}
>  
>  	ret = drm_of_find_panel_or_bridge(dev->of_node, 0, 0,
> -					  &dsi->panel, &dsi->next_bridge);
> +					  &panel, &dsi->next_bridge);
>  	if (ret)
>  		goto err_unregister_host;
>  
> +	if (panel) {
> +		dsi->panel_bridge = devm_drm_panel_bridge_add(dev, panel);

devm_drm_panel_bridge_add() can also return NULL on errors, so you need
IS_ERR_OR_NULL() below (and a special case to give ret a negative value
when the result is NULL). Or maybe it would be best to fix
devm_drm_panel_bridge_add() to always return an error pointer.

With this fixed,

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> +		if (IS_ERR(dsi->panel_bridge)) {
> +			ret = PTR_ERR(dsi->panel_bridge);
> +			goto err_unregister_host;
> +		}
> +	}
> +
>  	dsi->driver_data = of_device_get_match_data(dev);
>  
>  	dsi->engine_clk = devm_clk_get(dev, "engine");

-- 
Regards,

Laurent Pinchart