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From: Lukas Wunner <lukas@wunner.de>
To: Yicong Yang <yangyicong@hisilicon.com>
Cc: Bjorn Helgaas <helgaas@kernel.org>,
	Sathyanarayanan Kuppuswamy 
	<sathyanarayanan.kuppuswamy@linux.intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Ethan Zhao <haifeng.zhao@intel.com>,
	Sinan Kaya <okaya@kernel.org>, Ashok Raj <ashok.raj@intel.com>,
	Keith Busch <kbusch@kernel.org>,
	linux-pci@vger.kernel.org, Russell Currey <ruscur@russell.cc>,
	Oliver O'Halloran <oohall@gmail.com>,
	Stuart Hayes <stuart.w.hayes@gmail.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Linuxarm <linuxarm@huawei.com>
Subject: Re: [PATCH] PCI: pciehp: Ignore Link Down/Up caused by DPC
Date: Thu, 29 Apr 2021 21:42:14 +0200	[thread overview]
Message-ID: <20210429194214.GA22639@wunner.de> (raw)
In-Reply-To: <c7932c4e-81b1-279d-48df-5d621efff757@hisilicon.com>

On Thu, Apr 29, 2021 at 07:29:59PM +0800, Yicong Yang wrote:
> On 2021/4/28 22:40, Lukas Wunner wrote:
> > If DPC doesn't recover within 3 seconds, pciehp will consider the
> > error unrecoverable and bring down the slot, no matter what.
> > 
> > I can't tell you why DPC is unable to recover.  Does it help if you
> > raise the timeout to, say, 5000 msec?
> 
> I raise the timeout to 4s and it works well. I dump the remained jiffies in
> the log and find sometimes the recovery will take a bit more than 3s:

Thanks for testing.  I'll respin the patch and raise the timeout
to 4000 msec.

The 3000 msec were chosen arbitrarily.  I couldn't imagine that
it would ever take longer than that.  The spec does not seem to
mandate a time limit for DPC recovery.  But we do need a timeout
because the DPC Trigger Status bit may never clear and then pciehp
would wait indefinitely.  This can happen if dpc_wait_rp_inactive()
fails or perhaps because the hardware is buggy.

I'll amend the patch to clarify that the timeout is just a reasonable
heuristic and not a value provided by the spec.

Which hardware did you test this on?  Is this a HiSilicon platform
or Intel?

Thanks!

Lukas

  parent reply	other threads:[~2021-04-29 19:42 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-28  8:52 Lukas Wunner
2021-03-30 20:53 ` Kuppuswamy, Sathyanarayanan
2021-04-28  0:39   ` Kuppuswamy, Sathyanarayanan
2021-04-28  1:42     ` Zhao, Haifeng
2021-04-28 10:08 ` Yicong Yang
2021-04-28 14:40   ` Lukas Wunner
2021-04-29 11:29     ` Yicong Yang
2021-04-29 12:40       ` Zhao, Haifeng
2021-04-29 19:42       ` Lukas Wunner [this message]
2021-04-30  8:47         ` Yicong Yang
2021-04-30 12:15           ` Lukas Wunner
2021-04-29 19:36 ` Keith Busch
2021-04-29 20:16   ` Lukas Wunner
2021-04-29 21:16     ` Keith Busch

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