Hi,
On Wed, Jan 11, 2023 at 10:30:09AM -0600, Chris Morgan wrote:
> From: Chris Morgan <macromorgan@xxxxxxxxxxx>
>
> Add helper function to find DSI host for devices where DSI panel is not
> a minor of a DSI bus (such as the Samsung AMS495QA01 panel or the
> official Raspberry Pi touchscreen display).
>
> Signed-off-by: Chris Morgan <macromorgan@xxxxxxxxxxx>
> Signed-off-by: Maya Matuszczyk <maccraft123mc@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_of.c | 70 ++++++++++++++++++++++++++++++++++++++++
> include/drm/drm_of.h | 10 ++++++
> 2 files changed, 80 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index 7bbcb999bb75..4ebb5bc4b595 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -10,6 +10,7 @@
> #include <drm/drm_crtc.h>
> #include <drm/drm_device.h>
> #include <drm/drm_encoder.h>
> +#include <drm/drm_mipi_dsi.h>
> #include <drm/drm_of.h>
> #include <drm/drm_panel.h>
>
> @@ -493,3 +494,72 @@ int drm_of_get_data_lanes_count_ep(const struct device_node *port,
> return ret;
> }
> EXPORT_SYMBOL_GPL(drm_of_get_data_lanes_count_ep);
> +
> +/**
> + * drm_of_get_dsi_bus - find the DSI bus for a given device
> + * @dev: parent device of display (SPI, I2C)
> + * @info: DSI device info to be updated with correct DSI node
> + *
> + * Gets parent DSI bus for a DSI device controlled through a bus other
> + * than MIPI-DCS (SPI, I2C, etc.) using the Device Tree.
> + *
> + * Returns pointer to mipi_dsi_host if successful, -EINVAL if the
> + * request is unsupported, -EPROBE_DEFER if the DSI host is found but
> + * not available, or -ENODEV otherwise.
> + */
> +struct mipi_dsi_host *drm_of_get_dsi_bus(struct device *dev,
> + struct mipi_dsi_device_info *info)
> +{
> + struct mipi_dsi_host *dsi_host;
> + struct device_node *endpoint, *dsi_host_node;
> +
> + /*
> + * Exit immediately if we attempt to call this function when
> + * DRM_MIPI_DSI is not enabled, in the event CONFIG_OF is
> + * enabled.
> + */
> + if (!IS_ENABLED(CONFIG_DRM_MIPI_DSI))
> + return ERR_PTR(-EINVAL);
The commit log isn't super clear on why this is needed, but it would be
more consistent to add an ifdef and only compile the entire function if
DRM_MIPI_DSI is there, just like you did for OF already.
> + /*
> + * Get first endpoint child from device.
> + */
> + endpoint = of_graph_get_next_endpoint(dev->of_node, NULL);
> + if (!endpoint)
> + return ERR_PTR(-ENODEV);
> +
> + /*
> + * Follow the first endpoint to get the DSI host node.
> + */
> + dsi_host_node = of_graph_get_remote_port_parent(endpoint);
There's no need to hold the reference to endpoint after that call. call
of_node_put(endpoint) here, and it will simplify the error path.
> + if (!dsi_host_node)
> + goto error;
> +
> + /*
> + * Get the DSI host from the DSI host node. If we get an error
> + * or the return is null assume we're not ready to probe just
> + * yet. Release the DSI host node since we're done with it.
> + */
> + dsi_host = of_find_mipi_dsi_host_by_node(dsi_host_node);
> + of_node_put(dsi_host_node);
> + if (IS_ERR_OR_NULL(dsi_host)) {
> + of_node_put(endpoint);
> + return ERR_PTR(-EPROBE_DEFER);
> + }
> +
> + /*
> + * Set the node of the mipi_dsi_device_info to the correct node
> + * and then release the endpoint node since we're done with it.
> + */
> + info->node = of_graph_get_remote_port(endpoint);
Ah, you're using it there.
I think I'd rework the function to:
- retrieve the endpoint
- retrieve the remote port, give up the endpoint
- retrieve the remote port parent
Also, I'm not entirely sure what you had in mind, but info might not be
there at all and it would be fine imho.
Maxime
