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From:   Dan Williams <dan.j.williams@intel.com>
Date:   Tue, 15 Oct 2019 14:26:29 -0700
Message-ID: <CAPcyv4iRFZ3AZ6WOduDPxBu2sNUY3AJLO-81sWhkDityoeQAiw@mail.gmail.com>
Subject: Re: [PATCH] libata/ahci: Fix PCS quirk application
To:     Stephen Douthit <stephend@silicom-usa.com>
Cc:     "axboe@kernel.dk" <axboe@kernel.dk>,
        Andreas Friedrich <afrie@gmx.net>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Tue, Oct 15, 2019 at 2:02 PM Stephen Douthit
<stephend@silicom-usa.com> wrote:
>
> On 10/15/19 3:54 PM, Dan Williams wrote:
> > Commit c312ef176399 "libata/ahci: Drop PCS quirk for Denverton and
> > beyond" got the polarity wrong on the check for which board-ids should
> > have the quirk applied. The board type board_ahci_pcs7 is defined at the
> > end of the list such that "pcs7" boards can be special cased in the
> > future if they need the quirk. All prior Intel board ids "<
> > board_ahci_pcs7" should proceed with applying the quirk.
> >
> > Reported-by: Andreas Friedrich <afrie@gmx.net>
> > Reported-by: Stephen Douthit <stephend@silicom-usa.com>
> > Fixes: c312ef176399 ("libata/ahci: Drop PCS quirk for Denverton and beyond")
> > Cc: <stable@vger.kernel.org>
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> > ---
> >   drivers/ata/ahci.c |    4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> > index dd92faf197d5..05c2b32dcc4d 100644
> > --- a/drivers/ata/ahci.c
> > +++ b/drivers/ata/ahci.c
> > @@ -1600,7 +1600,9 @@ static void ahci_intel_pcs_quirk(struct pci_dev *pdev, struct ahci_host_priv *hp
> >        */
> >       if (!id || id->vendor != PCI_VENDOR_ID_INTEL)
> >               return;
>
> Unless I'm missing something this will short-circuit if there are any
> older Intel controllers not explicitly listed with a PCI_VDEVICE entry
> in ahci_pci_tbl.  Those will match on:
>
>         /* Generic, PCI class code for AHCI */
>         { PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID,
>           PCI_CLASS_STORAGE_SATA_AHCI, 0xffffff, board_ahci },

You're not missing anything, but I think we should stick with explicit
mapping as only newer controllers tend to match on class id rather
than pci-id, and there's no way to know if that class-id match is for
PCS_6 or PCS_7. Hopefully newer controllers are tested with Linux and
the BIOS fixed prior to the breakage leaking into the wild.