linux-kernel - Re: [PATCH v6] PCI: quirks: update Cavium ThunderX ACS quirk implementation

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Date:   Wed, 27 Sep 2017 14:18:54 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Vadim Lomovtsev <Vadim.Lomovtsev@...iumnetworks.com>
Cc:     bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, Wilson.Snyder@...ium.com
Subject: Re: [PATCH v6] PCI: quirks: update Cavium ThunderX ACS quirk
 implementation

On Wed, 27 Sep 2017 11:20:39 -0700
Vadim Lomovtsev <Vadim.Lomovtsev@...iumnetworks.com> wrote:

> This commit makes Cavium PCI ACS quirk applicable only to Cavium
> ThunderX (CN8XXX) family PCIE Root Ports which has limited PCI capabilities
> in terms of no ACS support advertisement. However, the RTL internally
> implements similar protection as if ACS had completion/request redirection,
> upstream forwarding and validation features enabled.
> 
> Current quirk implementation doesn't take into account PCIERCs which
> also needs to be quirked. So the pci device id check mask is updated
> and check of device ID moved into separate function.
> 
> Signed-off-by: Vadim Lomovtsev <Vadim.Lomovtsev@...iumnetworks.com>
> ---
> 	v5 -> v6: comment typo fix: change 0xa00 to 0xa000

Reviewed-by: Alex Williamson <alex.williamson@...hat.com>

 
>  drivers/pci/quirks.c | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index a4d3361..ed6c76d 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -4211,20 +4211,33 @@ static int pci_quirk_amd_sb_acs(struct pci_dev *dev, u16 acs_flags)
>  #endif
>  }
>  
> -static int pci_quirk_cavium_acs(struct pci_dev *dev, u16 acs_flags)
> +/*
> + * The Cavium downstream ports doesn't advertise their ACS capability registers.
> + * However, the RTL internally implements similar protection as if
> + * ACS had completion redirection, forwarding and validation features enabled.
> + * So by this flags we're asserting that the hardware implements and
> + * enables equivalent ACS functionality for these flags.
> + */
> +#define CAVIUM_CN8XXX_ACS_FLAGS (PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_SV | PCI_ACS_UF)
> +
> +static __inline__  bool pci_quirk_cavium_acs_match(struct pci_dev *dev)
>  {
>  	/*
> -	 * Cavium devices matching this quirk do not perform peer-to-peer
> -	 * with other functions, allowing masking out these bits as if they
> -	 * were unimplemented in the ACS capability.
> +	 * Effectively selects all downstream ports for whole ThunderX 1 family
> +	 * by 0xa000 mask (which represents 8 SoCs), while the lower bits of device ID
> +	 * are used to indicate which subdevice is used within the SoC.
>  	 */
> -	acs_flags &= ~(PCI_ACS_SV | PCI_ACS_TB | PCI_ACS_RR |
> -		       PCI_ACS_CR | PCI_ACS_UF | PCI_ACS_DT);
> +	return (pci_is_pcie(dev) &&
> +		(pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT) &&
> +		((dev->device & 0xf800) == 0xa000));
> +}
>  
> -	if (!((dev->device >= 0xa000) && (dev->device <= 0xa0ff)))
> +static int pci_quirk_cavium_acs(struct pci_dev *dev, u16 acs_flags)
> +{
> +	if (!pci_quirk_cavium_acs_match(dev))
>  		return -ENOTTY;
>  
> -	return acs_flags ? 0 : 1;
> +	return acs_flags & ~(CAVIUM_CN8XXX_ACS_FLAGS) ? 0 : 1;
>  }
>  
>  static int pci_quirk_xgene_acs(struct pci_dev *dev, u16 acs_flags)