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Date:   Tue, 9 Apr 2019 16:59:28 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Nikolai Kostrigin <nickel@altlinux.org>
Cc:     linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
        jroedel@suse.de, Alex Deucher <alexander.deucher@amd.com>
Subject: Re: [PATCH RESEND 1/1] PCI: Add ATS-disable quirk for AMD Radeon R7
 GPUs
Message-ID: <20190409215927.GC256045@google.com>
References: <20190408103725.30426-1-nickel@altlinux.org>
 <20190408103725.30426-2-nickel@altlinux.org>
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[+cc Alex]

This claims to be a resend, but I don't see a previous posting.

There *was* discussion when the quirk was added two years ago for a
different device.  As part of that, Alex thought only that device
would be affected and ATS was validated on other GPUs:

  https://lore.kernel.org/lkml/BN6PR12MB165278346BE8A76B1E4412AFF7EA0@BN6PR12MB1652.namprd12.prod.outlook.com/

On Mon, Apr 08, 2019 at 01:37:25PM +0300, Nikolai Kostrigin wrote:
> ATS is broken on this hardware (at least for Stoney Ridge
> based laptop) and causes IOMMU stalls and
> system failure. Disable ATS on these devices to make them
> usable again with IOMMU enabled
> Thanks to Joerg Roedel <jroedel@suse.de> for help.
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=194521
> 
> Signed-off-by: Nikolai Kostrigin <nickel@altlinux.org>

Joerg, I'm happy to merge this if you would review or ack it.  I don't
know enough to conclude that this is the root cause.  It'd be nice to
have an actual AMD erratum.  Maybe it would even have a list of
affected devices so we could get them all at once so people wouldn't
have to trip over them one by one.

> ---
>  drivers/pci/quirks.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 4700d24e5d55..abb2532e16bf 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -4876,6 +4876,7 @@ static void quirk_no_ats(struct pci_dev *pdev)
>  
>  /* AMD Stoney platform GPU */
>  DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x98e4, quirk_no_ats);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x6900, quirk_no_ats);
>  #endif /* CONFIG_PCI_ATS */
>  
>  /* Freescale PCIe doesn't support MSI in RC mode */
> -- 
> 2.21.0
>