Re: [PATCH v7 3/5] Add debugfs based silicon debug support in DWC

Krzysztof Wilczyński
2025-03-04T19:32:17Z

Hello,

[...]
> > > > > > + ret = dwc_pcie_rasdes_debugfs_init(pci, dir);
> > > > > > + if (ret)
> > > > > > + dev_dbg(dev, "RASDES debugfs init failed\n");
> > > > >
> > > > > What will happen if ret != 0? still return 0?
> > >
> > > And that is exactly what happens on Gray Hawk Single with R-Car
> > > V4M: dw_pcie_find_rasdes_capability() returns NULL, causing
> > > dwc_pcie_rasdes_debugfs_init() to return -ENODEV.
> >
> > Thank you for testing and for catching this issue. Much appreciated.
> >
> > > > Given that callers of dwc_pcie_debugfs_init() check for errors,
> > >
> > > Debugfs issues should never be propagated upstream!
> >
> > Makes complete sense. Sorry for breaking things here!
> >
> > > > this probably should correctly bubble up any failure coming from
> > > > dwc_pcie_rasdes_debugfs_init().
> > > >
> > > > I made updates to the code directly on the current branch, have a look:
> > >
> > > So while applying, you changed this like:
> > >
> > > ret = dwc_pcie_rasdes_debugfs_init(pci, dir);
> > > - if (ret)
> > > - dev_dbg(dev, "RASDES debugfs init failed\n");
> > > + if (ret) {
> > > + dev_err(dev, "failed to initialize RAS DES debugfs\n");
> > > + return ret;
> > > + }
> > >
> > > return 0;
> > >
> > > Hence this is now a fatal error, causing the probe to fail.
> >
> > I removed the changed, and also move the log level to be a warning, per:
> >
> > https://web.git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/commit/?h=controller/dwc&id=c6759a967e69aba16aef0d92f43e527b112e98a5
> >
> > Would this be acceptable here?
> >
> > Mani, would this be acceptable to you, too? Given that you posted the
> > following recently:
> >
> > https://lore.kernel.org/linux-pci/20250303200055.GA1881771@rocinante/T/#mab9cbd5834390d259afea056eee9a73d8c3b435f
> >
> > That said, perhaps moving the log level to a debug would be better served here.
> >
>
> Even though debugfs_init() failure is not supposed to fail the probe(),
> dwc_pcie_rasdes_debugfs_init() has a devm_kzalloc() and propagating that
> failure would be canolically correct IMO.
>
> So I would still opt to have my version + your previous one.

Sounds good!

I combined both changes (squashed your fix for the RAS DES capability
detection) together directly on the branch.

Thank you!

Krzysztof