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Date:   Wed, 7 Oct 2020 09:46:07 -0700
From:   Keith Busch <kbusch@kernel.org>
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc:     linux-pci@vger.kernel.org
Subject: Re: spammy dmesg about fluctuating pcie bandwidth on 5.9
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On Wed, Oct 07, 2020 at 06:09:06PM +0200, Jason A. Donenfeld wrote:
> Since 5.9 I've been seeing lots of the below in my logs. I'm wondering
> if this is a case of "ASPM finally working properly," or if I'm
> actually running into aberrant behavior that I should look into
> further. I run with `pcie_aspm=force pcie_aspm.policy=powersave` on my
> command line. But I wasn't seeing these messages in 5.8.
 
> [79960.801929] pcieport 0000:04:00.0: 31.504 Gb/s available PCIe bandwidth, limited by 8.0 GT/s PCIe x4 link at 0000:00:1b.4 (capable of 1984.941 Gb/s with 32.0 GT/s PCIe x63 link)

A x63 gen5 capable link?! No such encoding exists, so something is
definitely wrong. Looks like all 1's was returned when reading the link
capabilities register, as that equals the mask's 0x3f value. The code
ought to skip reporting a device returning all 1's.