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SubjectRe: [PATCH v8 04/10] drm: bridge: dw_mipi_dsi: allow bridge daisy chaining
Hi Adrian,

Thank you for the patch.

On Mon, Apr 27, 2020 at 11:19:46AM +0300, Adrian Ratiu wrote:
> Up until now the assumption was that the synopsis dsi bridge will
> directly connect to an encoder provided by the platform driver, but
> the current practice for drivers is to leave the encoder empty via
> the simple encoder API and add their logic to their own drm_bridge.
>
> Thus we need an ablility to connect the DSI bridge to another bridge
> provided by the platform driver, so we extend the dw_mipi_dsi bind()
> API with a new "previous bridge" arg instead of just hardcoding NULL.
>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
> ---
> New in v8.
> ---
> drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 6 ++++--
> drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c | 2 +-
> include/drm/bridge/dw_mipi_dsi.h | 5 ++++-
> 3 files changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> index 16fd87055e7b7..140ff40fa1b62 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> @@ -1456,11 +1456,13 @@ EXPORT_SYMBOL_GPL(dw_mipi_dsi_remove);
> /*
> * Bind/unbind API, used from platforms based on the component framework.
> */
> -int dw_mipi_dsi_bind(struct dw_mipi_dsi *dsi, struct drm_encoder *encoder)
> +int dw_mipi_dsi_bind(struct dw_mipi_dsi *dsi,
> + struct drm_encoder *encoder,
> + struct drm_bridge *prev_bridge)
> {
> int ret;
>
> - ret = drm_bridge_attach(encoder, &dsi->bridge, NULL, 0);
> + ret = drm_bridge_attach(encoder, &dsi->bridge, prev_bridge, 0);

Please note that chaining of bridges doesn't work well if multiple
bridges in the chain try to create a connector. This is why a
DRM_BRIDGE_ATTACH_NO_CONNECTOR flag has been added, with a helper to
create a connector for a chain of bridges (drm_bridge_connector_init()).
This won't play well with the component framework. I would recommend
using the of_drm_find_bridge() instead in the rockchip driver, and
deprecating dw_mipi_dsi_bind().

> if (ret) {
> DRM_ERROR("Failed to initialize bridge with drm\n");
> return ret;
> diff --git a/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c b/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c
> index 3feff0c45b3f7..83ef43be78135 100644
> --- a/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c
> +++ b/drivers/gpu/drm/rockchip/dw-mipi-dsi-rockchip.c
> @@ -929,7 +929,7 @@ static int dw_mipi_dsi_rockchip_bind(struct device *dev,
> return ret;
> }
>
> - ret = dw_mipi_dsi_bind(dsi->dmd, &dsi->encoder);
> + ret = dw_mipi_dsi_bind(dsi->dmd, &dsi->encoder, NULL);
> if (ret) {
> DRM_DEV_ERROR(dev, "Failed to bind: %d\n", ret);
> return ret;
> diff --git a/include/drm/bridge/dw_mipi_dsi.h b/include/drm/bridge/dw_mipi_dsi.h
> index b0e390b3288e8..699b3531f5b36 100644
> --- a/include/drm/bridge/dw_mipi_dsi.h
> +++ b/include/drm/bridge/dw_mipi_dsi.h
> @@ -14,6 +14,7 @@
> #include <drm/drm_modes.h>
>
> struct drm_display_mode;
> +struct drm_bridge;
> struct drm_encoder;
> struct dw_mipi_dsi;
> struct mipi_dsi_device;
> @@ -62,7 +63,9 @@ struct dw_mipi_dsi *dw_mipi_dsi_probe(struct platform_device *pdev,
> const struct dw_mipi_dsi_plat_data
> *plat_data);
> void dw_mipi_dsi_remove(struct dw_mipi_dsi *dsi);
> -int dw_mipi_dsi_bind(struct dw_mipi_dsi *dsi, struct drm_encoder *encoder);
> +int dw_mipi_dsi_bind(struct dw_mipi_dsi *dsi,
> + struct drm_encoder *encoder,
> + struct drm_bridge *prev_bridge);
> void dw_mipi_dsi_unbind(struct dw_mipi_dsi *dsi);
> void dw_mipi_dsi_set_slave(struct dw_mipi_dsi *dsi, struct dw_mipi_dsi *slave);
>

--
Regards,

Laurent Pinchart

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