linux-kernel - Re: [PATCH] PCI: Disallow ASPM on ASMedia ASM1083/1085 PCIe-PCI bridge

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Date:   Wed, 22 Jul 2020 18:46:06 -0600
From:   Robert Hancock <hancockrwd@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     linux-pci@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>, stable@...r.kernel.org,
        Puranjay Mohan <puranjay12@...il.com>
Subject: Re: [PATCH] PCI: Disallow ASPM on ASMedia ASM1083/1085 PCIe-PCI bridge

On Wed, Jul 22, 2020 at 11:40 AM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> [+cc Puranjay]
>
> On Tue, Jul 21, 2020 at 08:18:03PM -0600, Robert Hancock wrote:
> > Recently ASPM handling was changed to no longer disable ASPM on all
> > PCIe to PCI bridges. Unfortunately these ASMedia PCIe to PCI bridge
> > devices don't seem to function properly with ASPM enabled, as they
> > cause the parent PCIe root port to cause repeated AER timeout errors.
> > In addition to flooding the kernel log, this also causes the machine
> > to wake up immediately after suspend is initiated.
>
> Hi Robert, thanks a lot for the report of this problem
> (https://lore.kernel.org/r/CADLC3L1R2hssRjxHJv9yhdN_7-hGw58rXSfNp-FraZh0Tw+gRw@mail.gmail.com
> and https://bugzilla.redhat.com/show_bug.cgi?id=1853960).
>
> I'm pretty sure Linux ASPM support is missing some things.  This
> problem might be a hardware problem where a quirk is the right
> solution, but it could also be that it's a result of a Linux defect
> that we should fix.
>
> Could you collect the dmesg log and "sudo lspci -vvxxxx" output
> somewhere (maybe a bugzilla.kernel.org issue)?  I want to figure out
> whether this L1 PM substates are enabled on this link, and whether
> that's configured correctly.

Created a Bugzilla entry and added dmesg and lspci output:
https://bugzilla.kernel.org/show_bug.cgi?id=208667

As I noted in that report, I subsequently found this page on ASMedia's
site: https://www.asmedia.com.tw/eng/e_show_products.php?cate_index=169&item=114
which indicates this ASM1083 device has "No PCIe ASPM support". It's
not clear why this problem isn't occurring on Windows however - either
it is not enabling ASPM, somehow it doesn't cause issues with the PCIe
link, or it is causing issues and just doesn't notify the user in any
way. I can try and check if this bridge device is ending up with ASPM
enabled under Windows 10 or not..