On Tue, Jan 17, 2023 at 05:58:19PM +0100, Maxime Ripard wrote:
> Hi,
>
> On Thu, Jan 12, 2023 at 11:53:55AM -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..6c2c97a716fe 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);
> > +
> > +#if IS_ENABLED(CONFIG_DRM_MIPI_DSI)
> > +
> > +/**
> > + * 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 DSI node. This is optional
> > + * and if not needed can be NULL.
> > + *
> > + * 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;
> > +
> > + /*
> > + * 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);
> > + 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.
> > + * since this is optional, check if the info is NULL first.
> > + */
> > + if (info) {
> > + info->node = of_graph_get_remote_port(endpoint);
>
> it looks to me that the info->node is actually the DSI device OF node,
> not its host port. Which begs the question, why should we even return it
> there, since there's a pretty big chance that dev->of.node ==
> info->node, and you obviously don't care about the channel and type fields.
>
> I've had a look and node of the current users of
> mipi_dsi_device_register_full actually register a mipi_dsi_device_info
> with a node pointer set to !NULL, including the driver in this series.
>
> So, why do we care about the device info at all?
>
I honestly thought it might be useful, but I can try without it.
> > + if (IS_ERR_OR_NULL(info->node))
>
> of_graph_get_remote_port doesn't return an error pointer.
>
> > --- a/include/drm/drm_of.h
> > +++ b/include/drm/drm_of.h
> > @@ -15,6 +15,8 @@ struct drm_encoder;
> > struct drm_panel;
> > struct drm_bridge;
> > struct device_node;
> > +struct mipi_dsi_device_info;
> > +struct mipi_dsi_host;
> >
> > /**
> > * enum drm_lvds_dual_link_pixels - Pixel order of an LVDS dual-link connection
> > @@ -56,6 +58,8 @@ int drm_of_get_data_lanes_count_ep(const struct device_node *port,
> > int port_reg, int reg,
> > const unsigned int min,
> > const unsigned int max);
> > +struct mipi_dsi_host *drm_of_get_dsi_bus(struct device *dev,
> > + struct mipi_dsi_device_info *info);
> > #else
> > static inline uint32_t drm_of_crtc_port_mask(struct drm_device *dev,
> > struct device_node *port)
> > @@ -127,6 +131,12 @@ drm_of_get_data_lanes_count_ep(const struct device_node *port,
> > {
> > return -EINVAL;
> > }
> > +static inline struct
> > +mipi_dsi_host *drm_of_get_dsi_bus(struct device *dev,
> > + struct mipi_dsi_device_info *info)
> > +{
> > + return ERR_PTR(-EINVAL);
> > +}
> > #endif
>
> So it looks to me that if CONFIG_OF is defined, we'll define an external
> symbol declared for drm_of_get_dsi_bus, but that function will only be
> compiled if CONFIG_DRM_MIPI_DSI is enabled.
>
> What happens if we have CONFIG_OF but not CONFIG_DRM_MIPI_DSI?
>
Will do, thank you.
> If think you need to have here something like:
>
> #ifdef IS_ENABLED(CONFIG_OF) && IS_ENABLED(CONFIG_DRM_MIPI_DSI)
> struct mipi_dsi_host *drm_of_get_dsi_bus(struct device *dev,
> struct mipi_dsi_device_info *info);
> #else
> static inline struct
> mipi_dsi_host *drm_of_get_dsi_bus(struct device *dev,
> struct mipi_dsi_device_info *info)
> {
> return ERR_PTR(-EINVAL);
> }
> #endif
>
> Maxime
