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From: Srinath Mannam <srinath.mannam@broadcom.com>
Date: Thu, 14 Sep 2017 22:58:24 +0530
Message-ID: <CABe79T7WObM+LOGdPFfYC7hf0dKrhm5NwMgQ3DpcWst3eP6kNg@mail.gmail.com> (sfid-20170914_192830_595503_92F2E0FA)
Subject: Re: iwlwifi firmware load broken in current -git
To: Jens Axboe <axboe@kernel.dk>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
        Johannes Berg <johannes@sipsolutions.net>,
        Luca Coelho <luca@coelho.fi>,
        "Grumbach, Emmanuel" <emmanuel.grumbach@intel.com>,
        linuxwifi <linuxwifi@intel.com>,
        "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>
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Sender: linux-wireless-owner@vger.kernel.org

Hi Bjorn,

On Thu, Sep 14, 2017 at 10:52 PM, Jens Axboe <axboe@kernel.dk> wrote:
>
> On 09/14/2017 11:11 AM, Bjorn Helgaas wrote:
> > [+cc linux-pci]
> >
> > On Thu, Sep 14, 2017 at 12:00 PM, Jens Axboe <axboe@kernel.dk> wrote:
> >> On 09/12/2017 02:04 PM, Johannes Berg wrote:
> >>> On Tue, 2017-09-12 at 13:43 -0600, Jens Axboe wrote:
> >>>
> >>>> CC'ing the guilty part and Bjorn. I'm assuming it's the
> >>>> pci_is_enabled() check, since the rest of the patch shouldn't have
> >>>> functional changes.
> >>>
> >>> and pci_enable_bridge() already checks if it's already enabled, but
> >>> still enables mastering in that case if it isn't:
> >>>
> >>> static void pci_enable_bridge(struct pci_dev *dev)
> >>> {
> >>> [...]
> >>>         if (pci_is_enabled(dev)) {
> >>>                 if (!dev->is_busmaster)
> >>>                         pci_set_master(dev);
> >>>                 return;
> >>>         }
> >>>
> >>> so I guess due to the new check we end up with mastering disabled, and
> >>> thus the firmware can't load since that's a DMA thing?
> >>
> >> Bjorn/Srinath, any input here? This is a regression that prevents wifi
> >> from working on a pretty standard laptop. It'd suck to have this be in
> >> -rc1. Seems like the trivial fix would be:
> >>
> >>
> >> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> >> index b0002daa50f3..ffbe11dbdd61 100644
> >> --- a/drivers/pci/pci.c
> >> +++ b/drivers/pci/pci.c
> >> @@ -1394,7 +1394,7 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
> >>                 return 0;               /* already enabled */
> >>
> >>         bridge = pci_upstream_bridge(dev);
> >> -       if (bridge && !pci_is_enabled(bridge))
> >> +       if (bridge)
With this change and keeping "mutex_lock(&pci_bridge_mutex);" in
pci_enable_bridge functoin will causes a nexted lock.

> >>                 pci_enable_bridge(bridge);
> >>
> >>         /* only skip sriov related */
> >>
> >>
> >
> > Looks like a reasonable fix.  I assume it works for you?  I don't have
> > a way to test it, so if you can verify that it works and supply a
> > Signed-off-by, I can merge it.
>
> Booting it right now, I'll send out a proper version in a few minutes.
>
> --
> Jens Axboe
>