On Fri, 27 Sept 2024 at 08:41, Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx> wrote: > > On 27/09/2024 02:26, Dmitry Baryshkov wrote: > > 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). > > Do you mean that I should already see FWNODE_FLAG_NOT_DEVICE set in the > fwnode? No, I think you should set it for you DSS links. If I understand correctly, this should prevent fwdevlink from waiting on the OLDI to materialize as a device. Note: my understanding is based on a quick roaming through the code some time ago. > > If I print information about the relevant fwnodes (from dss up to the > oldi endpoints) in the DSS driver's probe, I see that none have > FWNODE_FLAG_NOT_DEVICE set, all have FWNODE_FLAG_LINKS_ADDED set, and > only the main DSS node has the fwnode->dev set (to 30200000.dss). > > Tomi > > >> > >>> 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
