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

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Message-ID: <20230330021016.GA30164@L-PF27918B-1352.localdomain>
Date:   Thu, 30 Mar 2023 10:10:16 +0800
From:   Wu Zongyong <wuzongyong@...ux.alibaba.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
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 12:05:15PM -0500, Bjorn Helgaas wrote:
> 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.
Will be fixed.
> 
> 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.
Yes, this problem occurs only when the T4 card is direct attached to a
Root Port.
I have test it with a T4 card attached to a PCIe Switch or a PCI Bridge,
and it works well.

> 
> > 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
Will be fixed too.
> 
> Are there any problem reports or bugzilla issues you can include a URL
> to?
No, I just find the problem in our test environment and I didn't find a
similar report.
> 
> > 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
> >