Hi,
We've encountered an issue with the RaspberryPi DSI panel that prevented the whole display driver from probing.
The issue is described in detail in the commit 7213246a803f ("drm/vc4: dsi: Only register our component once a DSI device is attached"), but the basic idea is that since the panel is probed through i2c, there's no synchronization between its probe and the registration of the MIPI-DSI host it's attached to.
We initially moved the component framework registration to the MIPI-DSI Host attach hook to make sure we register our component only when we have a DSI device attached to our MIPI-DSI host, and then use lookup our DSI device in our bind hook.
However, all the DSI bridges controlled through i2c are only registering their associated DSI device in their bridge attach hook, meaning with our change above, we never got that far, and therefore ended up in the same situation than the one we were trying to fix for panels.
The best practice to avoid those issues is to register its functions only after all its dependencies are live. We also shouldn't wait any longer than we should to play nice with the other components that are waiting for us, so in our case that would mean moving the DSI device registration to the bridge probe.
If the general approach is agreed upon, other bridge drivers will obviously be converted.
Let me know what you think, Maxime
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Changes from v2: - Changed the approach as suggested by Andrzej, and aligned the bridge on the panel this time. - Fixed some typos
Changes from v1: - Change the name of drm_of_get_next function to drm_of_get_bridge - Mention the revert of 87154ff86bf6 and squash the two patches that were reverting that commit - Add some documentation - Make drm_panel_attach and _detach succeed when no callback is there
Maxime Ripard (8): drm/bridge: Add documentation sections drm/bridge: Document the probe issue with MIPI-DSI bridges drm/mipi-dsi: Create devm device registration drm/mipi-dsi: Create devm device attachment drm/bridge: ps8640: Switch to devm MIPI-DSI helpers drm/bridge: ps8640: Register and attach our DSI device at probe drm/bridge: sn65dsi83: Switch to devm MIPI-DSI helpers drm/bridge: sn65dsi83: Register and attach our DSI device at probe
Documentation/gpu/drm-kms-helpers.rst | 12 ++++ drivers/gpu/drm/bridge/parade-ps8640.c | 97 ++++++++++++++------------ drivers/gpu/drm/bridge/ti-sn65dsi83.c | 82 +++++++++++----------- drivers/gpu/drm/drm_bridge.c | 70 +++++++++++++++++-- drivers/gpu/drm/drm_mipi_dsi.c | 81 +++++++++++++++++++++ include/drm/drm_mipi_dsi.h | 4 ++ 6 files changed, 256 insertions(+), 90 deletions(-)