linux-kernel - Re: [RFC PATCH] PCI: avoid SBR for NVIDIA T4

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Date:   Wed, 29 Mar 2023 12:05:15 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Wu Zongyong <wuzongyong@...ux.alibaba.com>
Cc:     sdonthineni@...dia.com, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        wllenyj@...ux.alibaba.com, wutu.xq2@...ux.alibaba.com,
        gerry@...ux.alibaba.com
Subject: Re: [RFC PATCH] PCI: avoid SBR for NVIDIA T4

On Wed, Mar 29, 2023 at 07:58:45PM +0800, Wu Zongyong wrote:
> Secondary bus reset will fail if NVIDIA T4 card is direct attached to a
> root port.

Blank line between paragraphs.  Rewrap to fill 75 columns if it's a
single paragraph.

Is this only a problem when direct attached to a Root Port?  Why would
that be?  If it's *not* related to being directly under a Root Port,
don't mention that at all.

> So avoid to do bus reset,  pci_parent_bus_reset() works nomarlly.
> 
> Maybe NVIDIA guys can do some detailed explanation abount the SBR
> behaviour of GPUs.

This is a follow-on to 4c207e7121fa ("PCI: Mark some NVIDIA GPUs to
avoid bus reset"), so probably should have a Fixes: tag so it goes
whereever that commit goes.

Also copy the subject line from 4c207e7121fa, e.g.,

  PCI: Mark NVIDIA T4 GPUs to avoid bus reset

Are there any problem reports or bugzilla issues you can include a URL
to?

> Signed-off-by: Wu Zongyong <wuzongyong@...ux.alibaba.com>
> ---
>  drivers/pci/quirks.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 44cab813bf95..be86b93b9e38 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -3618,7 +3618,7 @@ static void quirk_no_bus_reset(struct pci_dev *dev)
>   */
>  static void quirk_nvidia_no_bus_reset(struct pci_dev *dev)
>  {
> -	if ((dev->device & 0xffc0) == 0x2340)
> +	if ((dev->device & 0xffc0) == 0x2340 || dev->device == 0x1eb8)
>  		quirk_no_bus_reset(dev);
>  }
>  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_NVIDIA, PCI_ANY_ID,
> -- 
> 2.34.3
>