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Date:   Fri, 17 Apr 2020 00:45:57 +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 7/7] drm/mediatek: mtk_dsi: Create connector for
 bridges
Message-ID: <20200416214557.GC28162@pendragon.ideasonboard.com>
References: <20200416155720.2360443-1-enric.balletbo@collabora.com>
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Hi Enric,

On Thu, Apr 16, 2020 at 11:33:24PM +0200, Enric Balletbo i Serra wrote:
> On 16/4/20 19:36, Laurent Pinchart wrote:
> > On Thu, Apr 16, 2020 at 08:35:26PM +0300, Laurent Pinchart wrote:
> >> On Thu, Apr 16, 2020 at 05:57:19PM +0200, Enric Balletbo i Serra wrote:
> >>> Use the drm_bridge_connector helper to create a connector for pipelines
> >>> that use drm_bridge. This allows splitting connector operations across
> >>> multiple bridges when necessary, instead of having the last bridge in
> >>> the chain creating the connector and handling all connector operations
> >>> internally.
> >>
> >> That's the right direction, but this should be done in the mtk display
> >> controller driver core, not in here. I'm OK with the code being here as
> >> an interim measure if needed to move forward, but that should then be
> >> temporary only.
> 
> It'd be nice if we can do this as an interim measure for now, so at least we
> have the embedded display working. IIUC to move that to the display controller
> driver core I should also convert/rework the mtk_dpi and mtk_hdmi drivers. This
> is used for the external display on my device but to fully support this I'll
> also need to rework the bridge chain logic to handle the multi-sink/multi-source
> use case. This is something I plan to work on but I suspect won't be easy and
> will trigger lots of discussions, and, of course, some time.
> 
> So, if is fine I won't move this for now.

That's totally fine with me, I just wanted to make sure you were aware
that more work was needed :-)

Thanks for all your efforts !

> > I forgot to mention that the drm_encoder should also move out of the
> > bridge driver to the display controller driver.
> > 
> >>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> >>> ---
> >>>
> >>> Changes in v2: None
> >>>
> >>>  drivers/gpu/drm/mediatek/mtk_dsi.c | 14 +++++++++++++-
> >>>  1 file changed, 13 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> >>> index 44718fa3d1ca..2f8876c32864 100644
> >>> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> >>> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> >>> @@ -17,6 +17,7 @@
> >>>  
> >>>  #include <drm/drm_atomic_helper.h>
> >>>  #include <drm/drm_bridge.h>
> >>> +#include <drm/drm_bridge_connector.h>
> >>>  #include <drm/drm_mipi_dsi.h>
> >>>  #include <drm/drm_of.h>
> >>>  #include <drm/drm_panel.h>
> >>> @@ -184,6 +185,7 @@ struct mtk_dsi {
> >>>  	struct drm_bridge bridge;
> >>>  	struct drm_bridge *panel_bridge;
> >>>  	struct drm_bridge *next_bridge;
> >>> +	struct drm_connector *connector;
> >>>  	struct phy *phy;
> >>>  
> >>>  	void __iomem *regs;
> >>> @@ -983,10 +985,19 @@ static int mtk_dsi_encoder_init(struct drm_device *drm, struct mtk_dsi *dsi)
> >>>  	 */
> >>>  	dsi->encoder.possible_crtcs = 1;
> >>>  
> >>> -	ret = drm_bridge_attach(&dsi->encoder, &dsi->bridge, NULL, 0);
> >>> +	ret = drm_bridge_attach(&dsi->encoder, &dsi->bridge, NULL,
> >>> +				DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> >>>  	if (ret)
> >>>  		goto err_cleanup_encoder;
> >>>  
> >>> +	dsi->connector = drm_bridge_connector_init(drm, &dsi->encoder);
> >>> +	if (IS_ERR(dsi->connector)) {
> >>> +		DRM_ERROR("Unable to create bridge connector\n");
> >>> +		ret = PTR_ERR(dsi->connector);
> >>> +		goto err_cleanup_encoder;
> >>> +	}
> >>> +	drm_connector_attach_encoder(dsi->connector, &dsi->encoder);
> >>> +
> >>>  	return 0;
> >>>  
> >>>  err_cleanup_encoder:
> >>> @@ -1144,6 +1155,7 @@ static int mtk_dsi_probe(struct platform_device *pdev)
> >>>  
> >>>  	dsi->bridge.funcs = &mtk_dsi_bridge_funcs;
> >>>  	dsi->bridge.of_node = dev->of_node;
> >>> +	dsi->bridge.type = DRM_MODE_CONNECTOR_DSI;
> >>
> >> I think this line belongs to the patch that adds drm_bridge support to
> >> this driver.
> >>
> >>>  
> >>>  	drm_bridge_add(&dsi->bridge);
> >>>  

-- 
Regards,

Laurent Pinchart