linux-kernel - Re: [PATCH] PCI/DPC: Extend DPC recovery timeout

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Message-ID: <aJPOmw2c8LGW2qN7@kbusch-mbp>
Date: Wed, 6 Aug 2025 15:52:27 -0600
From: Keith Busch <kbusch@...nel.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Lukas Wunner <lukas@...ner.de>, Hongbo Yao <andy.xu@...micro.com>,
	Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	bhelgaas@...gle.com, mahesh@...ux.ibm.com, oohall@...il.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	jemma.zhang@...micro.com, peter.du@...micro.com
Subject: Re: [PATCH] PCI/DPC: Extend DPC recovery timeout

On Wed, Aug 06, 2025 at 04:34:09PM -0500, Bjorn Helgaas wrote:
> > > However, the current 4 seconds timeout in pci_dpc_recovered() is indeed
> > > an empirical value rather than a hard requirement from the PCIe
> > > specification. In real-world scenarios, like with Mellanox ConnectX-5/7
> > > adapters, we've observed that full DPC recovery can take more than 5-6
> > > seconds, which leads to premature hotplug processing and device removal.
> > 
> > I think Sathya's point was:  Have you made an effort to talk to the
> > vendor and ask them to root-cause and fix the issue e.g. with a firmware
> > update.
> 
> Would definitely be great, but unless we have a number in the spec to
> point to, they might just shrug and ask what the requirement is.

I agree, and I have similar problems with other arbitrary kernel timing
decicsions. Specifically RRL where there's no spec defined number yet my
patch to modify it has not received much consideration.

  https://lore.kernel.org/linux-pci/20250218165444.2406119-1-kbusch@meta.com/