linux-kernel - Re: [PATCH] PCI: Add ACS quirk for Cavium ThunderX 2 root port devices

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Date:   Thu, 25 Jul 2019 16:35:02 +0000
From:   Jayachandran Chandrasekharan Nair <jnair@...vell.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     Shannon Zhao <shenglong.zsl@...baba-inc.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Guiping Duan <gduan@...vell.com>,
        George Cherian <gcherian@...vell.com>,
        "Sunil Kovvuri Goutham" <sgoutham@...vell.com>
Subject: Re: [PATCH] PCI: Add ACS quirk for Cavium ThunderX 2 root port
 devices

On Wed, Jul 24, 2019 at 01:55:35PM -0500, Bjorn Helgaas wrote:
> See
> https://lkml.kernel.org/r/20171026223701.GA25649@bhelgaas-glaptop.roam.corp.google.com
> for incidental hints (subject, commit log, commit reference).  Your
> patch basically extends that commit, so the subject should be very
> similar.
> 
> On Fri, Jul 19, 2019 at 09:10:35PM +0800, Shannon Zhao wrote:
> > From: Shannon Zhao <shannon.zhao@...ux.alibaba.com>
> > 
> > Like commit f2ddaf8(PCI: Apply Cavium ThunderX ACS quirk to more Root
> > Ports), it should apply ACS quirk to ThunderX 2 root port devices.
> 
> s/root port/Root Port/ to be consistent
> 
> > Signed-off-by: Shannon Zhao <shannon.zhao@...ux.alibaba.com>
> 
> I suppose this should have the same stable tag as f2ddaf8dfd4a ("PCI:
> Apply Cavium ThunderX ACS quirk to more Root Ports") itself?
> > ---
> >  drivers/pci/quirks.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> > index 28c64f8..ea7848b 100644
> > --- a/drivers/pci/quirks.c
> > +++ b/drivers/pci/quirks.c
> > @@ -4224,10 +4224,12 @@ static bool pci_quirk_cavium_acs_match(struct pci_dev *dev)
> >  	 * family by 0xf800 mask (which represents 8 SoCs), while the lower
> >  	 * bits of device ID are used to indicate which subdevice is used
> >  	 * within the SoC.
> > +	 * Effectively selects the ThunderX 2 root ports whose device ID
> > +	 * is 0xaf84.
> >  	 */
> >  	return (pci_is_pcie(dev) &&
> >  		(pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT) &&
> > -		((dev->device & 0xf800) == 0xa000));
> > +		((dev->device & 0xf800) == 0xa000 || dev->device == 0xaf84));
> 
> I'm somewhat doubtful about this because previously we at least
> selected a whole class of ThunderX 1 devices:
> 
>   ((dev->device & 0xf800) == 0xa000)
> 
> while you're adding only a *single* ThunderX device.
> 
> I don't want a constant trickle of adding new devices.  Can somebody
> from Cavium or Marvell provide a corresponding mask for ThunderX 2, or
> confirm that 0xaf84 is really the single device we expect to need
> here?
 
We are working on a patch to fix this quirk to handle more Marvell
(Cavium) PCI IDs. Ideally we should be handling ThunderX1, ThunderX2
and the Octeon-TX families here.

Adding the folks working on this reduce the churn here, hopefully
we can get all of it sorted in one patch.
 
JC