Re: [PATCH 0/2] Adjust AMD GPU ATS quirks

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Jan 14, 2020 at 05:41:44PM -0600, Bjorn Helgaas wrote:
> On Tue, Jan 14, 2020 at 03:55:21PM -0500, Alex Deucher wrote:
> > We've root caused the issue and clarified the quirk.
> > This also adds a new quirk for a new GPU.
> > 
> > Alex Deucher (2):
> >   pci: Clarify ATS quirk
> >   pci: add ATS quirk for navi14 board (v2)
> > 
> >  drivers/pci/quirks.c | 32 +++++++++++++++++++++++++-------
> >  1 file changed, 25 insertions(+), 7 deletions(-)
> 
> I propose the following, which I intend to be functionally identical.
> It just doesn't repeat the pci_info() and pdev->ats_cap = 0.

Applied to pci/misc for v5.6, thanks!

> commit 998c4f7975b0 ("PCI: Mark AMD Navi14 GPU rev 0xc5 ATS as broken")
> Author: Bjorn Helgaas <bhelgaas@google.com>
> Date:   Tue Jan 14 17:09:28 2020 -0600
> 
>     PCI: Mark AMD Navi14 GPU rev 0xc5 ATS as broken
>     
>     To account for parts of the chip that are "harvested" (disabled) due to
>     silicon flaws, caches on some AMD GPUs must be initialized before ATS is
>     enabled.
>     
>     ATS is normally enabled by the IOMMU driver before the GPU driver loads, so
>     this cache initialization would have to be done in a quirk, but that's too
>     complex to be practical.
>     
>     For Navi14 (device ID 0x7340), this initialization is done by the VBIOS,
>     but apparently some boards went to production with an older VBIOS that
>     doesn't do it.  Disable ATS for those boards.
>     
>     https://lore.kernel.org/r/20200114205523.1054271-3-alexander.deucher@amd.com
>     Bug: https://gitlab.freedesktop.org/drm/amd/issues/1015
>     See-also: d28ca864c493 ("PCI: Mark AMD Stoney Radeon R7 GPU ATS as broken")
>     See-also: 9b44b0b09dec ("PCI: Mark AMD Stoney GPU ATS as broken")
>     Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
>     Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 4937a088d7d8..fbeb9f73ef28 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -5074,18 +5074,25 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, 0x0422, quirk_no_ext_tags);
>  
>  #ifdef CONFIG_PCI_ATS
>  /*
> - * Some devices have a broken ATS implementation causing IOMMU stalls.
> - * Don't use ATS for those devices.
> + * Some devices require additional driver setup to enable ATS.  Don't use
> + * ATS for those devices as ATS will be enabled before the driver has had a
> + * chance to load and configure the device.
>   */
> -static void quirk_no_ats(struct pci_dev *pdev)
> +static void quirk_amd_harvest_no_ats(struct pci_dev *pdev)
>  {
> -	pci_info(pdev, "disabling ATS (broken on this device)\n");
> +	if (pdev->device == 0x7340 && pdev->revision != 0xc5)
> +		return;
> +
> +	pci_info(pdev, "disabling ATS\n");
>  	pdev->ats_cap = 0;
>  }
>  
>  /* 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);
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x98e4, quirk_amd_harvest_no_ats);
> +/* AMD Iceland dGPU */
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x6900, quirk_amd_harvest_no_ats);
> +/* AMD Navi14 dGPU */
> +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_ATI, 0x7340, quirk_amd_harvest_no_ats);
>  #endif /* CONFIG_PCI_ATS */
>  
>  /* Freescale PCIe doesn't support MSI in RC mode */