Hi Tomi, Thank you for the patch. On Fri, Jul 21, 2023 at 06:01:39PM +0300, Tomi Valkeinen wrote: > DRM bridges are not visible to the userspace and it may not be > immediately clear if the chain is somehow constructed incorrectly. I > have had two separate instances of a bridge driver failing to do a > drm_bridge_attach() call, resulting in the bridge connector not being > part of the chain. In some situations this doesn't seem to cause issues, > but it will if DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is used. > > Add a debugfs file to print the bridge chains. For me, on this TI AM62 > based platform, I get the following output: > > encoder[39] > bridge[0] type: 0, ops: 0x0 > bridge[1] type: 0, ops: 0x0, OF: /bus@f0000/i2c@20000000/dsi@e:toshiba,tc358778 > bridge[2] type: 0, ops: 0x3, OF: /bus@f0000/i2c@20010000/hdmi@48:lontium,lt8912b > bridge[3] type: 11, ops: 0x7, OF: /hdmi-connector:hdmi-connector Names would be more readable than numbers, but I'm not sure that's really worth it. It can always be improved on top if desired. > Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx> > --- > Changes in v2: > - Fixed compilation issue when !CONFIG_OF > - Link to v1: https://lore.kernel.org/r/20230721-drm-bridge-chain-debugfs-v1-1-8614ff7e890d@xxxxxxxxxxxxxxxx > --- > drivers/gpu/drm/drm_bridge.c | 50 +++++++++++++++++++++++++++++++++++++++++++ > drivers/gpu/drm/drm_debugfs.c | 3 +++ > include/drm/drm_bridge.h | 5 +++++ > 3 files changed, 58 insertions(+) > > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c > index c3d69af02e79..d3eb62d5ef3b 100644 > --- a/drivers/gpu/drm/drm_bridge.c > +++ b/drivers/gpu/drm/drm_bridge.c > @@ -27,8 +27,10 @@ > #include <linux/mutex.h> > > #include <drm/drm_atomic_state_helper.h> > +#include <drm/drm_debugfs.h> > #include <drm/drm_bridge.h> > #include <drm/drm_encoder.h> > +#include <drm/drm_file.h> > #include <drm/drm_of.h> > #include <drm/drm_print.h> > > @@ -1345,6 +1347,54 @@ struct drm_bridge *of_drm_find_bridge(struct device_node *np) > EXPORT_SYMBOL(of_drm_find_bridge); > #endif > > +#ifdef CONFIG_DEBUG_FS > +static int drm_bridge_chains_info(struct seq_file *m, void *data) > +{ > + struct drm_debugfs_entry *entry = m->private; > + struct drm_device *dev = entry->dev; > + struct drm_printer p = drm_seq_file_printer(m); > + struct drm_mode_config *config = &dev->mode_config; As Alexander reported, there's a crash for GPU drivers, as mode_config isn't initialized in that case. I would skip creating the debugfs entry if DRIVER_MODESET isn't set. > + struct drm_encoder *encoder; > + unsigned int bridge_idx = 0; > + > + list_for_each_entry(encoder, &config->encoder_list, head) { > + struct drm_bridge *bridge; > + > + drm_printf(&p, "encoder[%u]\n", encoder->base.id); > + > + bridge = drm_bridge_chain_get_first_bridge(encoder); > + > + while (bridge) { Would drm_for_each_bridge_in_chain() help ? > + drm_printf(&p, "\tbridge[%u] type: %u, ops: %#x", > + bridge_idx, bridge->type, bridge->ops); > + > +#ifdef CONFIG_OF > + if (bridge->of_node) > + drm_printf(&p, ", OF: %pOFfc", bridge->of_node); > +#endif > + > + drm_printf(&p, "\n"); > + > + bridge_idx++; > + bridge = drm_bridge_get_next_bridge(bridge); > + } > + } > + > + return 0; > +} > + > +/* any use in debugfs files to dump individual planes/crtc/etc? */ Those can easily be listed from userspace, so I don't think that's needed. > +static const struct drm_debugfs_info drm_bridge_debugfs_list[] = { > + {"bridge_chains", drm_bridge_chains_info, 0}, Missing spaces after '{' and before '}'. > +}; > + > +void drm_bridge_debugfs_init(struct drm_minor *minor) > +{ > + drm_debugfs_add_files(minor->dev, drm_bridge_debugfs_list, > + ARRAY_SIZE(drm_bridge_debugfs_list)); > +} > +#endif > + > MODULE_AUTHOR("Ajay Kumar <ajaykumar.rs@xxxxxxxxxxx>"); > MODULE_DESCRIPTION("DRM bridge infrastructure"); > MODULE_LICENSE("GPL and additional rights"); > diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c > index c90dbcffa0dc..3e89559d68cd 100644 > --- a/drivers/gpu/drm/drm_debugfs.c > +++ b/drivers/gpu/drm/drm_debugfs.c > @@ -31,6 +31,7 @@ > > #include <drm/drm_atomic.h> > #include <drm/drm_auth.h> > +#include <drm/drm_bridge.h> > #include <drm/drm_client.h> > #include <drm/drm_debugfs.h> > #include <drm/drm_device.h> > @@ -272,6 +273,8 @@ int drm_debugfs_init(struct drm_minor *minor, int minor_id, > > drm_debugfs_add_files(minor->dev, drm_debugfs_list, DRM_DEBUGFS_ENTRIES); > > + drm_bridge_debugfs_init(minor); > + > if (drm_drv_uses_atomic_modeset(dev)) { > drm_atomic_debugfs_init(minor); > } > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h > index bf964cdfb330..60dbee6bd1e6 100644 > --- a/include/drm/drm_bridge.h > +++ b/include/drm/drm_bridge.h > @@ -949,4 +949,9 @@ static inline struct drm_bridge *drmm_of_get_bridge(struct drm_device *drm, > } > #endif > > +#ifdef CONFIG_DEBUG_FS You could drop the conditional compilation, it wouldn't hurt. > +struct drm_minor; > +void drm_bridge_debugfs_init(struct drm_minor *minor); > +#endif > + > #endif > > --- > base-commit: c7a472297169156252a50d76965eb36b081186e2 > change-id: 20230721-drm-bridge-chain-debugfs-0bbc1522f57a -- Regards, Laurent Pinchart
