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

Krzysztof Wilczyński
2025-03-04T16:59:16Z

Hello,

> This patch is now commit 1ff54f4cbaed9ec6 ("PCI: dwc: Add debugfs
> based Silicon Debug support for DWC") in pci/next (next-20250304).
>
> On Mon, 3 Mar 2025 at 20:47, Krzysztof Wilczyński <kw@linux.com> wrote:
> > [...]
> > > > +int dwc_pcie_debugfs_init(struct dw_pcie *pci)
> > > > +{
> > > > + char dirname[DWC_DEBUGFS_BUF_MAX];
> > > > + struct device *dev = pci->dev;
> > > > + struct debugfs_info *debugfs;
> > > > + struct dentry *dir;
> > > > + int ret;
> > > > +
> > > > + /* Create main directory for each platform driver */
> > > > + snprintf(dirname, DWC_DEBUGFS_BUF_MAX, "dwc_pcie_%s", dev_name(dev));
> > > > + dir = debugfs_create_dir(dirname, NULL);
> > > > + debugfs = devm_kzalloc(dev, sizeof(*debugfs), GFP_KERNEL);
> > > > + if (!debugfs)
> > > > + return -ENOMEM;
> > > > +
> > > > + debugfs->debug_dir = dir;
> > > > + pci->debugfs = debugfs;
> > > > + 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.

Krzysztof