linux-kernel - Re: [PATCH 4/4] PCI: quirk Atheros AR93xx to avoid bus reset

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Date:	Thu, 8 Jan 2015 09:07:33 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] PCI: quirk Atheros AR93xx to avoid bus reset

On Fri, Nov 21, 2014 at 11:24:27AM -0700, Alex Williamson wrote:
> Reports against the TL-WDN4800 card indicate that PCI bus reset of
> this Atheros device cause system lock-ups and resets.  I've also
> been able to confirm this behavior on multiple systems.  The device
> never returns from reset and attempts to access config space of the
> device after reset result in hangs.  Blacklist bus reset for the
> device to avoid this issue.
> 
> Reported-by: Andreas Hartmann <andihartmann@...enet.de>
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> Tested-by: Andreas Hartmann <andihartmann@...enet.de>

If I understand correctly, these two (patches 3 & 4) fix a v3.14 regression
caused by 425c1b223dac ("PCI: Add Virtual Channel to save/restore support").

If so, these should go to for-linus for v3.19.  What about patches 1 & 2?
Do they fix a regression?  Is there a pointer to a bugzilla or problem
report about that issue?

I don't understand the connection between 425c1b223dac and
PCI_DEV_FLAGS_NO_BUS_RESET, because 425c1b223dac doesn't seem to do any
resets.  Is that the wrong commit, or can you outline the connection for
me?

Bjorn

> ---
> 
>  drivers/pci/quirks.c |   14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 561e10d..ebbd5b4 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -3029,6 +3029,20 @@ static void quirk_no_pm_reset(struct pci_dev *dev)
>  DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_VENDOR_ID_ATI, PCI_ANY_ID,
>  			       PCI_CLASS_DISPLAY_VGA, 8, quirk_no_pm_reset);
>  
> +static void quirk_no_bus_reset(struct pci_dev *dev)
> +{
> +	dev->dev_flags |= PCI_DEV_FLAGS_NO_BUS_RESET;
> +}
> +
> +/*
> + * Atheros AR93xx chips do not behave after a bus reset.  The device will
> + * throw a Link Down error on AER capable system and regardless of AER,
> + * config space of the device is never accessible again and typically
> + * causes the system to hang or reset when access is attempted.
> + * http://www.spinics.net/lists/linux-pci/msg34797.html
> + */
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATHEROS, 0x0030, quirk_no_bus_reset);
> +
>  #ifdef CONFIG_ACPI
>  /*
>   * Apple: Shutdown Cactus Ridge Thunderbolt controller.
> 
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