From: Keith Busch <kbusch@kernel.org>
To: Lukas Wunner <lukas@wunner.de>
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>,
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>
Subject: Re: [PATCH] PCI: pciehp: Ignore Link Down/Up caused by DPC
Date: Fri, 30 Apr 2021 04:36:48 +0900 [thread overview]
Message-ID: <20210429193648.GA26517@redsun51.ssa.fujisawa.hgst.com> (raw)
In-Reply-To: <b70e19324bbdded90b728a5687aa78dc17c20306.1616921228.git.lukas@wunner.de>
On Sun, Mar 28, 2021 at 10:52:00AM +0200, Lukas Wunner wrote:
> Downstream Port Containment (PCIe Base Spec, sec. 6.2.10) disables the
> link upon an error and attempts to re-enable it when instructed by the
> DPC driver.
>
> A slot which is both DPC- and hotplug-capable is currently brought down
> by pciehp once DPC is triggered (due to the link change) and brought up
> on successful recovery. That's undesirable, the slot should remain up
> so that the hotplugged device remains bound to its driver. DPC notifies
> the driver of the error and of successful recovery in pcie_do_recovery()
> and the driver may then restore the device to working state.
This is a bit strange. The PCIe spec says DPC capable ports suppress
Link Down events specifically because it will confuse hot-plug
surprise ports if you don't do that. I'm specifically looking at the
"Implementation Note" in PCIe Base Spec 5.0 section 6.10.2.4.
Do these ports have out-of-band Precense Detect capabilities? If so, we
can ignore Link Down events on DPC capable ports as long as PCIe Slot
Status PDC isn't set.
next prev parent reply other threads:[~2021-04-29 19:37 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-28 8:52 [PATCH] PCI: pciehp: Ignore Link Down/Up caused by DPC 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
2021-04-30 8:47 ` Yicong Yang
2021-04-30 12:15 ` Lukas Wunner
2021-04-29 19:36 ` Keith Busch [this message]
2021-04-29 20:16 ` Lukas Wunner
2021-04-29 21:16 ` Keith Busch
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