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

Andrew Murray
2019-08-22T08:31:49Z

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...

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
>