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?
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.
