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

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Message-ID: <20250304175841.GF2310180@rocinante>
Date: Wed, 5 Mar 2025 02:58:41 +0900
From: Krzysztof Wilczyński <kw@...ux.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>, Fan Ni <nifan.cxl@...il.com>,
	Shradha Todi <shradha.t@...sung.com>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-perf-users@...r.kernel.org, lpieralisi@...nel.org,
	robh@...nel.org, bhelgaas@...gle.com, jingoohan1@...il.com,
	Jonathan.Cameron@...wei.com, a.manzanares@...sung.com,
	pankaj.dubey@...sung.com, cassel@...nel.org, 18255117159@....com,
	xueshuai@...ux.alibaba.com, renyu.zj@...ux.alibaba.com,
	will@...nel.org, mark.rutland@....com,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v7 3/5] Add debugfs based silicon debug support in DWC

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