linux-kernel - Re: [PATCH] pci/doe: add a 1 second retry window to pci

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Message-ID: <66e51febbab99_ae212949d@dwillia2-mobl3.amr.corp.intel.com.notmuch>
Date: Fri, 13 Sep 2024 22:32:28 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: Gregory Price <gourry@...rry.net>, <linux-pci@...r.kernel.org>
CC: <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<bhelgaas@...gle.com>, <dan.j.williams@...el.com>, <dave@...olabs.net>,
	<jonathan.cameron@...wei.com>, <dave.jiang@...el.com>,
	<vishal.l.verma@...el.com>, <linux-pci@...r.kernel.org>, <lukas@...ner.de>
Subject: Re: [PATCH] pci/doe: add a 1 second retry window to pci_doe

[ add linux-pci and Lukas ]

Gregory Price wrote:
> Depending on the device, sometimes firmware clears the busy flag
> later than expected.  This can cause the device to appear busy when
> calling multiple commands in quick sucession. Add a 1 second retry
> window to all doe commands that end with -EBUSY.

I would have expected this to be handled as part of finishing off
pci_doe_recv_resp() not retrying on a new submission.

It also occurs to me that instead of warning "another entity is sending conflicting
requests" message, the doe core should just ensure that it is the only
agent using the mailbox. Something like hold the PCI config lock over
DOE transactions. Then it will remove ambiguity of "conflicting agent"
vs "device is slow to clear BUSY".