linux-kernel - Re: [PATCH v5 2/7] PCI: Add ACS quirk for Amazon Annapurna Labs root ports

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Message-ID: <329373c70adfe37fc5288b9fac9e438447412693.camel@amazon.com>
Date:   Wed, 11 Sep 2019 14:59:29 +0000
From:   "Chocron, Jonathan" <jonnyc@...zon.com>
To:     "helgaas@...nel.org" <helgaas@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "jingoohan1@...il.com" <jingoohan1@...il.com>,
        "Woodhouse, David" <dwmw@...zon.co.uk>,
        "Hanoch, Uri" <hanochu@...zon.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "gustavo.pimentel@...opsys.com" <gustavo.pimentel@...opsys.com>,
        "Wasserstrom, Barak" <barakw@...zon.com>,
        "Saidi, Ali" <alisaidi@...zon.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "andrew.murray@....com" <andrew.murray@....com>,
        "Hawa, Hanna" <hhhawa@...zon.com>,
        "Shenhar, Talel" <talel@...zon.com>,
        "Krupnik, Ronen" <ronenk@...zon.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        "Chocron, Jonathan" <jonnyc@...zon.com>
Subject: Re: [PATCH v5 2/7] PCI: Add ACS quirk for Amazon Annapurna Labs root
 ports

On Sat, 2019-09-07 at 11:54 -0500, Bjorn Helgaas wrote:
> On Thu, Sep 05, 2019 at 05:00:16PM +0300, Jonathan Chocron wrote:
> > From: Ali Saidi <alisaidi@...zon.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@...zon.com>
> > Signed-off-by: Jonathan Chocron <jonnyc@...zon.com>
> > Reviewed-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>
> > Reviewed-by: Andrew Murray <andrew.murray@....com>
> 
> Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>
> 
> But please tweak it as below ...
> 
Will be part of v6.

> > ---
> >  drivers/pci/quirks.c | 20 ++++++++++++++++++++
> >  1 file changed, 20 insertions(+)
> > 
> > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > index ded60757a573..8fe765592943 100644
> > --- a/drivers/pci/quirks.c
> > +++ b/drivers/pci/quirks.c
> > @@ -4418,6 +4418,24 @@ 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.
> > +	 */
> > +	acs_flags &= ~(PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_SV |
> > PCI_ACS_UF);
> 
> There are several quirks that use this same set of bits, but they
> don't use the same order, which is a needless difference.
> 
> Can you reorder them in the bit 0 ... bit 7 order?  I.e.,
> 
>     PCI_ACS_SV | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF
> 
Done.

> > +	if (pci_pcie_type(dev) != PCI_EXP_TYPE_ROOT_PORT)
> > +		return -ENOTTY;
> 
> This could go first (above the comment) so all the acs_flags stuff is
> together.
> 
Done.

> > +	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,
> > @@ -4611,6 +4629,8 @@ 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
> >