linux-kernel - Re: Issues with "PCI/LINK: Report degraded links via link bandwidth notification"

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Message-ID: <20200130162606.GB6377@lst.de>
Date:   Thu, 30 Jan 2020 17:26:06 +0100
From:   Christoph Hellwig <hch@....de>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Alexandru Gagniuc <mr.nuke.me@...il.com>,
        Alexandru Gagniuc <alex_gagniuc@...lteam.com>,
        Keith Busch <keith.busch@...el.com>, Jens Axboe <axboe@...com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jan Vesely <jano.vesely@...il.com>,
        Lukas Wunner <lukas@...ner.de>,
        Alex Williamson <alex.williamson@...hat.com>,
        Austin Bolen <austin_bolen@...l.com>,
        Shyam Iyer <Shyam_Iyer@...l.com>,
        Sinan Kaya <okaya@...nel.org>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: Issues with "PCI/LINK: Report degraded links via link
 bandwidth notification"

On Sun, Jan 19, 2020 at 08:33:26PM -0600, Bjorn Helgaas wrote:
> NVMe, GPU folks, do your drivers or devices change PCIe link
> speed/width for power saving or other reasons?  When CONFIG_PCIE_BW=y,
> the PCI core interprets changes like that as problems that need to be
> reported.

The NVMe driver doesn't.  For devices I don't know of any, but Ican't
find anything in the spec that would forbid it.