On Tue, Jul 7, 2020 at 3:26 AM Maxime Ripard maxime@cerno.tech wrote:
If the DSI driver is the last to probe, component_add will try to run all the bind callbacks straight away and return the error code.
However, since we depend on a power domain, we're pretty much guaranteed to be in that case on the BCM2711, and are just lucky on the previous SoCs since the v3d also depends on that power domain and is further in the probe order.
In that case, the DSI host will not stick around in the system: the DSI bind callback will be executed, will not find any DSI device attached and will return EPROBE_DEFER, and we will then remove the DSI host and ask to be probed later on.
But since that host doesn't stick around, DSI devices like the RaspberryPi touchscreen whose probe is not linked to the DSI host (unlike the usual DSI devices that will be probed through the call to mipi_dsi_host_register) cannot attach to the DSI host, and we thus end up in a situation where the DSI host cannot probe because the panel hasn't probed yet, and the panel cannot probe because the DSI host hasn't yet.
In order to break this cycle, let's wait until there's a DSI device that attaches to the DSI host to register the component and allow to progress further.
Suggested-by: Andrzej Hajda a.hajda@samsung.com Signed-off-by: Maxime Ripard maxime@cerno.tech
I feel like I've written this patch before, but I've thankfully forgotten most of my battle with DSI probing. As long as this still lets vc4 probe in the absence of a DSI panel in the DT as well, then this is enthusiastically acked.