linux-kernel - PCI: Work around PCIe link training failures

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Message-Id: <20240806000659.30859-1-mattc@purestorage.com>
Date: Mon,  5 Aug 2024 18:06:59 -0600
From: Matthew W Carlis <mattc@...estorage.com>
To: macro@...am.me.uk
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Subject: PCI: Work around PCIe link training failures

Hello again. I just realized that my first response to this thread two weeks
ago was not actually starting from the end of the discussion. I hope I found
it now... Must say sorry for this I am still figuring out how to follow these
threads.
I need to ask if we can either revert this patch or only modify the quirk to
only run on the device in mention (ASMedia ASM2824). We have now identified
it as causing devices to get stuck at Gen1 in multiple generations of our
hardware & across product lines on ports were hot-plug is common. To be a
little more specific it includes Intel root ports and Broadcomm PCIe switch
ports and also Microchip PCIe switch ports.
The most common place where we see our systems getting stuck at Gen1 is with
device power cycling. If a device is powered on and then off quickly then the
link will of course fail to train & the consequence here is that the port is
forced to Gen1 forever. Does anybody know why the patch will only remove the
forced Gen1 speed from the ASMedia device?

- Matt