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

From: "Chocron, Jonathan" <jonnyc@amazon.com>
To: "andrew.murray@arm.com" <andrew.murray@arm.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"robh+dt@kernel.org" <robh+dt@kernel.org>,
	"jingoohan1@gmail.com" <jingoohan1@gmail.com>,
	"Woodhouse, David" <dwmw@amazon.co.uk>,
	"Hanoch, Uri" <hanochu@amazon.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"lorenzo.pieralisi@arm.com" <lorenzo.pieralisi@arm.com>,
	"gustavo.pimentel@synopsys.com" <gustavo.pimentel@synopsys.com>,
	"Wasserstrom, Barak" <barakw@amazon.com>,
	"Saidi, Ali" <alisaidi@amazon.com>,
	"mark.rutland@arm.com" <mark.rutland@arm.com>,
	"Hawa, Hanna" <hhhawa@amazon.com>,
	"Shenhar, Talel" <talel@amazon.com>,
	"Krupnik, Ronen" <ronenk@amazon.com>,
	"bhelgaas@google.com" <bhelgaas@google.com>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	"benh@kernel.crashing.org" <benh@kernel.crashing.org>,
	"Chocron, Jonathan" <jonnyc@amazon.com>
Subject: Re: [PATCH v4 2/7] PCI: Add ACS quirk for Amazon Annapurna Labs root ports
Date: Wed, 4 Sep 2019 13:33:20 +0000	[thread overview]
Message-ID: <81d37cda067a9880a261cbddf6051f9a89a3bc76.camel@amazon.com> (raw)
In-Reply-To: <20190822083144.GL23903@e119886-lin.cambridge.arm.com>

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
> >