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Date: Mon, 21 Sep 2026 14:01:39 -0500
From: Bjorn Helgaas <helgaas@kernel.org>
To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Cc: Lukas Wunner <lukas@wunner.de>, Bjorn Helgaas <bhelgaas@google.com>,
	linux-pci@vger.kernel.org, linux-acpi@vger.kernel.org,
	linux-kernel@vger.kernel.org, Rafael J Wysocki <rafael@kernel.org>,
	Guixin Liu <kanie@linux.alibaba.com>,
	Olof Johansson <olof@lixom.net>
Subject: Re: [PATCH v13 1/5] PCI/DPC: Ignore devices with no AER Capability
Message-ID: <20260921190139.GA1333023@bhelgaas>
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In-Reply-To: <24b9db58-e654-408b-85a9-15c5af5e944a@linux.intel.com>

On Mon, Sep 21, 2026 at 09:43:43AM -0700, Kuppuswamy Sathyanarayanan wrote:
> Hi Lukas,
> 
> On 9/19/2026 11:11 PM, Lukas Wunner wrote:
> > On Sat, Sep 19, 2026 at 09:26:51AM -0700, Kuppuswamy Sathyanarayanan wrote:
> >> Downstream Ports may support DPC regardless of whether they support AER
> >> (see PCIe r7.0, sec 6.2.11.2).  Previously, if the user booted with
> >> "pcie_ports=dpc-native", it was possible for dpc_probe() to succeed even if
> >> the device had no AER Capability, but dpc_get_aer_uncorrect_severity()
> >> depends on the AER Capability.
> > [...]
> >> +++ b/drivers/pci/pcie/dpc.c
> >> @@ -477,6 +477,9 @@ static int dpc_probe(struct pcie_device *dev)
> >>  	int status;
> >>  	u16 cap;
> >>  
> >> +	if (!pdev->aer_cap)
> >> +		return -ENOTSUPP;
> >> +
> >>  	if (!pcie_aer_is_native(pdev) && !pcie_ports_dpc_native)
> >>  		return -ENOTSUPP;
> > 
> > I've got patches which make DPC work (again) on AER-unsupporting ports:
> > 
> >   https://github.com/l1k/linux/commits/aer_baseline_v1/
> > 
> > In particular:
> > 
> >   PCI/DPC: Avoid access to non-existent AER capability
> >   https://github.com/l1k/linux/commit/85f209fd4732
> > 
> >   PCI/DPC: Reinstate support for AER-incapable ports
> >   https://github.com/l1k/linux/commit/2de89b762d79
> > 
> > I'm almost done with that series and hope to submit it this cycle.
> > Your patch [1/5] will cause a conflict with my patches.
> > Would you mind holding off on patch [1/5] for now?
> 
> Sure. At first glance, your series fixes the AER/DPC dependency
> cleanly.
> 
> I think we can drop this patch. Bjorn, let me know if you think
> otherwise.

OK.  [1/5] can be dropped cleanly with no resulting merge conflicts.
I'll wait to move ahead until the comments on [2/5] are resolved.