Re: mhi resume failure on reboot with 6.13-rc2

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Wed, Dec 18, 2024 at 01:02:39PM +0100, Johan Hovold wrote:
> On Wed, Dec 18, 2024 at 05:08:30PM +0530, Manivannan Sadhasivam wrote:
> > On Wed, Dec 18, 2024 at 09:40:45AM +0100, Johan Hovold wrote:
> 
> > > I've tracked down the hang to a deadlock on the parent device lock.
> > > 
> > > Driver core takes the parent device lock before calling shutdown(), and
> > > then mhi_pci_shutdown() waits indefinitely for the recovery thread to
> > > finish.
> 
> > Thanks for tracking the deadlock. I think we should use pci_try_reset_function()
> > instead of pci_reset_function() in mhi_pci_recovery_work().
> > 
> > If the pci_dev_lock() is already taken, it will return with -EAGAIN and we do
> > not need to worry in that case since the host is going to be powered off anyway
> > (and so the device).
> 
> That may work. But note that I've now also seen this deadlock during
> suspend (i.e. when the device is not going away). The
> pci_try_reset_function() should avoid the deadlock here too, but we'll
> end up in funny state.
> 

Hopefully, recovery_work() started by mhi_pci_runtime_resume() would be able to
reset the device.

> Now I'd also like to know why I'm suddenly seeing these runtime PM
> resume errors of this modem. Haven't seen them before 6.13-rc, and I'm
> not sure that it's really the firmware that is crashing left and right
> all of a sudden.
> 

Yeah, that's worth the effort. I'll go ahead with the patch since the issue is
present anyway.

- Mani

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