Re: [PATCH v4 2/7] PCI: Add ACS quirk for Amazon Annapurna Labs root ports

Chocron, Jonathan
2019-09-04T13:33:33Z

On Thu, 2019-08-22 at 09:31 +0100, Andrew Murray wrote:
> On Wed, Aug 21, 2019 at 06:35:42PM +0300, Jonathan Chocron wrote:
> > From: Ali Saidi <alisaidi@amazon.com>
> >
> > The Amazon's Annapurna Labs root ports don't advertise an ACS
> > capability, but they don't allow peer-to-peer transactions and do
> > validate bus numbers through the SMMU. Additionally, it's not
> > possible
> > for one RP to pass traffic to another RP.
> >
> > Signed-off-by: Ali Saidi <alisaidi@amazon.com>
> > Signed-off-by: Jonathan Chocron <jonnyc@amazon.com>
> > Reviewed-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
> > ---
> > drivers/pci/quirks.c | 19 +++++++++++++++++++
> > 1 file changed, 19 insertions(+)
> >
> > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > index 208aacf39329..23672680dba7 100644
> > --- a/drivers/pci/quirks.c
> > +++ b/drivers/pci/quirks.c
> > @@ -4366,6 +4366,23 @@ static int pci_quirk_qcom_rp_acs(struct
> > pci_dev *dev, u16 acs_flags)
> > return ret;
> > }
> >
> > +static int pci_quirk_al_acs(struct pci_dev *dev, u16 acs_flags)
> > +{
> > + /*
> > + * Amazon's Annapurna Labs root ports don't include an ACS
> > capability,
> > + * but do include ACS-like functionality. The hardware doesn't
> > support
> > + * peer-to-peer transactions via the root port and each has a
> > unique
> > + * segment number.
> > + * Additionally, the root ports cannot send traffic to each
> > other.
>
> Nit: I'd probably put a new line between the above two lines, or
> start the
> 'Additionally' sentence on the first line. But either way...
>
Added a newline.

> Reviewed-by: Andrew Murray <andrew.murray@arm.com>
>
>
> > + */
> > + acs_flags &= ~(PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_SV |
> > PCI_ACS_UF);
> > +
> > + if (pci_pcie_type(dev) != PCI_EXP_TYPE_ROOT_PORT)
> > + return -ENOTTY;
> > +
> > + return acs_flags ? 0 : 1;
> > +}
> > +
> > /*
> > * Sunrise Point PCH root ports implement ACS, but unfortunately
> > as shown in
> > * the datasheet (Intel 100 Series Chipset Family PCH Datasheet,
> > Vol. 2,
> > @@ -4559,6 +4576,8 @@ static const struct pci_dev_acs_enabled {
> > { PCI_VENDOR_ID_AMPERE, 0xE00A, pci_quirk_xgene_acs },
> > { PCI_VENDOR_ID_AMPERE, 0xE00B, pci_quirk_xgene_acs },
> > { PCI_VENDOR_ID_AMPERE, 0xE00C, pci_quirk_xgene_acs },
> > + /* Amazon Annapurna Labs */
> > + { PCI_VENDOR_ID_AMAZON_ANNAPURNA_LABS, 0x0031, pci_quirk_al_acs
> > },
> > { 0 }
> > };
> >
> > --
> > 2.17.1
> >