Re: [PATCH v1 1/5] driver core: fw_devlink: Improve handling of cyclic dependencies

[Rob Herring]

On Mon, Sep 13, 2021 at 11:39 PM Saravana Kannan <saravanak@xxxxxxxxxx> wrote:
>
> When we have a dependency of the form:
>
> Device-A -> Device-C
>         Device-B
>
> Device-C -> Device-B
>
> Where,
> * Indentation denotes "child of" parent in previous line.
> * X -> Y denotes X is consumer of Y based on firmware (Eg: DT).
>
> We have cyclic dependency: device-A -> device-C -> device-B -> device-A
>
> fw_devlink current treats device-C -> device-B dependency as an invalid
> dependency and doesn't enforce it but leaves the rest of the
> dependencies as is.
>
> While the current behavior is necessary, it is not sufficient if the
> false dependency in this example is actually device-A -> device-C. When
> this is the case, device-C will correctly probe defer waiting for
> device-B to be added, but device-A will be incorrectly probe deferred by
> fw_devlink waiting on device-C to probe successfully. Due to this, none
> of the devices in the cycle will end up probing.
>
> To fix this, we need to go relax all the dependencies in the cycle like
> we already do in the other instances where fw_devlink detects cycles.
> A real world example of this was reported[1] and analyzed[2].
>
> [1] - https://lore.kernel.org/lkml/0a2c4106-7f48-2bb5-048e-8c001a7c3fda@xxxxxxxxxxx/
> [2] - https://lore.kernel.org/lkml/CAGETcx8peaew90SWiux=TyvuGgvTQOmO4BFALz7aj0Za5QdNFQ@xxxxxxxxxxxxxx/
> Fixes: f9aa460672c9 ("driver core: Refactor fw_devlink feature")
> Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx>
> ---
>  drivers/base/core.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)

Am I supposed to apply this? What about the revert and mdio-parent-bus
support you mentioned? Those are needed too? Please send me a series
with what I should apply for 5.15, not fixes and new features
combined.

Rob