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SubjectRe: [PATCH v4 2/4] drm: sun4i: dsi: Add bridge support
Hi Jagan,

Thank you for the patch.

On Mon, Mar 22, 2021 at 07:31:50PM +0530, Jagan Teki wrote:
> Some display panels would come up with a non-DSI output which

Did you mean input instead of output ?

> can have an option to connect DSI interface by means of bridge
> converter.
>
> This DSI to non-DSI bridge converter would require a bridge
> driver that would communicate the DSI controller for bridge
> functionalities.
>
> So, add support for bridge functionalities in Allwinner DSI
> controller.
>
> Cc: Samuel Holland <samuel@sholland.org>
> Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> ---
> Note:
> Samuel Holland, The existing kms hotplug dropped in order to
> attach the bridge properly.
>
> However, I did try several ways to support hotplug with the
> bridge but it's resulting in a deadlock where bind never attach
> bridge until bridge pointer found and bridge pointer cannot
> found until bind finishes. Any inputs on this would be appreciated.
>
> Changes for v4:
> - none
> Changes for v3:
> - updated with new API's
>
> drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 34 +++++++++++++++++---------
> drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h | 2 +-
> 2 files changed, 23 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index 2e9e7b2d4145..39321299dc27 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -773,6 +773,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
> if (dsi->panel)
> drm_panel_prepare(dsi->panel);
>
> + if (dsi->panel_bridge)
> + dsi->panel_bridge->funcs->pre_enable(dsi->panel_bridge);
> +
> /*
> * FIXME: This should be moved after the switch to HS mode.
> *
> @@ -788,6 +791,9 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
> if (dsi->panel)
> drm_panel_enable(dsi->panel);
>
> + if (dsi->panel_bridge)
> + dsi->panel_bridge->funcs->enable(dsi->panel_bridge);
> +
> sun6i_dsi_start(dsi, DSI_START_HSC);
>
> udelay(1000);
> @@ -804,6 +810,9 @@ static void sun6i_dsi_encoder_disable(struct drm_encoder *encoder)
> if (dsi->panel) {
> drm_panel_disable(dsi->panel);
> drm_panel_unprepare(dsi->panel);
> + } else if (dsi->panel_bridge) {
> + dsi->panel_bridge->funcs->disable(dsi->panel_bridge);
> + dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
> }

Instead of having code paths that depend on whether you have a panel or
a bridge, it would be better to wrap the panel a bridge (using
drivers/gpu/drm/bridge/panel.c). The dsi->panel_bridge pointer should be
renamed to next_bridge, and all the code (except in probe) can the use
next_bridge without caring if it's a direct connection to a panel or
another bridge.

Furthermore, the encoder should call bridge functions explicitly, this
should be handled by the DRM core.

>
> phy_power_off(dsi->dphy);
> @@ -964,23 +973,17 @@ static int sun6i_dsi_attach(struct mipi_dsi_host *host,
> struct mipi_dsi_device *device)
> {
> struct sun6i_dsi *dsi = host_to_sun6i_dsi(host);
> - struct drm_panel *panel;
> int ret;
>
> ret = drm_of_find_panel_or_bridge(dsi->dev->of_node, 0, 0,
> - &panel, NULL);
> + &dsi->panel, &dsi->panel_bridge);
> if (ret)
> return ret;
>
> - if (!dsi->drm || !dsi->drm->registered)
> - return -EPROBE_DEFER;
> -
> - dsi->panel = panel;
> dsi->device = device;
>
> - drm_kms_helper_hotplug_event(dsi->drm);
> -
> - dev_info(host->dev, "Attached device %s\n", device->name);
> + dev_info(host->dev, "Attached %s %s\n",
> + device->name, dsi->panel ? "panel" : "bridge");
>
> return 0;
> }
> @@ -991,9 +994,10 @@ static int sun6i_dsi_detach(struct mipi_dsi_host *host,
> struct sun6i_dsi *dsi = host_to_sun6i_dsi(host);
>
> dsi->panel = NULL;
> + dsi->panel_bridge = NULL;
> dsi->device = NULL;
>
> - drm_kms_helper_hotplug_event(dsi->drm);
> + drm_of_panel_bridge_remove(dsi->dev->of_node, 0, 0);
>
> return 0;
> }
> @@ -1082,7 +1086,13 @@ static int sun6i_dsi_bind(struct device *dev, struct device *master,
>
> drm_connector_attach_encoder(&dsi->connector, &dsi->encoder);
>
> - dsi->drm = drm;
> + if (dsi->panel_bridge) {
> + ret = drm_bridge_attach(&dsi->encoder, dsi->panel_bridge, NULL, 0);
> + if (ret) {
> + dev_err(dsi->dev, "Couldn't attach drm bridge\n");
> + goto err_cleanup_connector;
> + }
> + }
>
> return 0;
>
> @@ -1096,7 +1106,7 @@ static void sun6i_dsi_unbind(struct device *dev, struct device *master,
> {
> struct sun6i_dsi *dsi = dev_get_drvdata(dev);
>
> - dsi->drm = NULL;
> + drm_encoder_cleanup(&dsi->encoder);
> }
>
> static const struct component_ops sun6i_dsi_ops = {
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> index c863900ae3b4..370ecb356a63 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> @@ -29,8 +29,8 @@ struct sun6i_dsi {
>
> struct device *dev;
> struct mipi_dsi_device *device;
> - struct drm_device *drm;
> struct drm_panel *panel;
> + struct drm_bridge *panel_bridge;
> };
>
> static inline struct sun6i_dsi *host_to_sun6i_dsi(struct mipi_dsi_host *host)

--
Regards,

Laurent Pinchart

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