Re: PCI driver - hotplug of multiple devices

[Lukas Wunner <lukas@wunner.de>]

On Wed, Jul 22, 2026 at 07:12:24AM +0000, Jozef Matejcik (Nokia) wrote:
> The driver is Broadcom's linux-kernel-bde.

This seems to be an out-of-tree driver, i.e. not something that is
part of the mainline kernel.  The upstream community can only provide
very limited support for such drivers.  The vendor needs to upstream
the driver into the mainline kernel, otherwise there's only so much
we can do.

> The issue:
>  - kernel module is inserted
>  - we de-assert reset of these PCI devices (previously in reset, i.e.
>    effectively powered down)
>  - sometimes, very infrequently, the box freezes for 1-3 minutes and
>    the HW triggers reboot

We'd need logs to say anything about it.

> When we removed the module before de-asserting the resets and then
> inserted it later, the issue did not occur. So we suspect that the
> kernel driver is accessing the device during probe too early and
> this is causing HW freeze.

Or maybe the reset puts the device in a state which is unexpected by
the driver.

> Are PCI drivers expected to handle hotplug events of any number of
> their devices simultaneously?

Yes.  E.g. a global data structure in the driver needs to be properly
locked if accessed concurrently by the probe function for separate
devices.

> Can the issue I described above be considered a bug in vendor's
> implementation?

Sounds like it.  Usually out-of-tree drivers haven't gone through
the rigorous review process by the community and quality may thus
be subpar.  The recommendation is to ask vendors whether driver
support is in mainline already when selecting components for your
products.

Thanks,

Lukas