On Mon, Sep 16, 2024 at 02:51:57PM GMT, Tomi Valkeinen wrote: > Hi, > > We have an issue where two devices have dependencies to each other, > according to drivers/base/core.c's fw_devlinks, and this prevents them from > probing. I've been adding debugging to the core.c, but so far I don't quite > grasp the issue, so I thought to ask. Maybe someone can instantly say that > this just won't work... Well, just 2c from my side. I consider that fw_devlink adds devlinks for of-graph nodes to be a bug. It doesn't know about the actual direction of dependencies between corresponding devices or about the actual relationship between drivers. It results in a loop which is then broken in some way. Sometimes this works. Sometimes it doesn't. Sometimes this hides actual dependencies between devices. I tried reverting offending parts of devlink, but this attempt failed. > > If I understand the fw_devlink code correctly, in a normal case the links > formed with media graphs are marked as a cycle (FWLINK_FLAG_CYCLE), and then > ignored as far as probing goes. > > What we see here is that when using a single-link OLDI panel, the panel > driver's probe never gets called, as it depends on the OLDI, and the link > between the panel and the OLDI is not a cycle. I think in your case you should be able to fix the issue by using the FWNODE_FLAG_NOT_DEVICE, which is intented to be used in such cases. You have a dependency on DT node which doesn't have backing device. > > The DSS driver probes, but the probe fails as it requires all the panel > devices to have been probed (and thus registered to the DRM framework) > before it can finish its setup. > -- With best wishes Dmitry
