RE: [PATCH v2] PCI: Add ATS-disable quirk for AMD Stoney GPUs

[Deucher, Alexander]

> -----Original Message-----
> From: Joerg Roedel [mailto:joro@xxxxxxxxxx]
> Sent: Friday, April 07, 2017 10:32 AM
> To: Bjorn Helgaas
> Cc: linux-pci@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Daniel Drake;
> Deucher, Alexander; Samuel Sieb; David Woodhouse; Joerg Roedel
> Subject: [PATCH v2] PCI: Add ATS-disable quirk for AMD Stoney GPUs
> 
> From: Joerg Roedel <jroedel@xxxxxxx>
> 
> ATS is broken on this hardware and causes IOMMU stalls and
> system failure. Disable ATS on these devices to make them
> usable again with IOMMU enabled.
> 
> Note that the commit in the Fixes-tag is not buggy, it
> just uncovers the problem in the hardware by increasing
> the ATS-flush rate.
> 
> Fixes: b1516a14657a ('iommu/amd: Implement flush queue')
> Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>

Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>

> ---
>  drivers/pci/quirks.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 6736836..7cbe316 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -4634,3 +4634,22 @@ static void quirk_no_aersid(struct pci_dev *pdev)
>  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x2031,
> quirk_no_aersid);
>  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x2032,
> quirk_no_aersid);
>  DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x2033,
> quirk_no_aersid);
> +
> +#ifdef CONFIG_PCI_ATS
> +/*
> + * Some devices have a broken ATS implementation causing IOMMU stalls.
> + * Don't use ATS for those devices.
> + */
> +static void quirk_disable_ats(struct pci_dev *pdev)
> +{
> +	/*
> +	 * Set pdev->ats_cap = 0 to make pci_enable_ats() bail out
> +	 * early.
> +	 */
> +	dev_info(&pdev->dev, "QUIRK: Disabling ATS");
> +	pdev->ats_cap = 0;
> +}
> +
> +/* AMD Stoney platform GPU */
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x98e4,
> quirk_disable_ats);
> +#endif /* CONFIG_PCI_ATS */
> --
> 1.9.1