On Thu, Sep 26, 2024 at 02:52:35PM GMT, Tomi Valkeinen wrote: > Hi, > > On 21/09/2024 23:15, Dmitry Baryshkov wrote: > > 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. > > I was also wondering about this. The of-graphs are always two-way links, so > the system must always mark them as a cycle. But perhaps there are other > benefits in the devlinks than dependency handling? > > > > 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 > > How would I go using FWNODE_FLAG_NOT_DEVICE? Won't this only make a > difference if the flag is there at early stage when the linux devices are > being created? I think it's too late if I set the flag when the dss driver > is being probed. I think you have the NOT_DEVICE case as the DSS device corresponds to the parent of your OLDI nodes. There is no device which corresponds to the oldi@0 / oldi@1 device nodes (which contain corresponding port nodes). > > > have a dependency on DT node which doesn't have backing device. > > Well, there is a backing device, the DSS. But if you mean that the system at > the moment cannot figure out that there is a backing device, then true. -- With best wishes Dmitry
