linux-kernel - Re: [PATCH] PCI: Add quirk for Cavium Thunder-X2 PCIe erratum #173

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Message-ID: <20180222083543.GA14945@wunner.de>
Date:   Thu, 22 Feb 2018 09:35:43 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     George Cherian <gcherian@...iumnetworks.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        bhelgaas@...gle.com, Jayachandran.Nair@...ium.com,
        Robert.Richter@...ium.com,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Huang Ying <ying.huang@...el.com>
Subject: Re: [PATCH] PCI: Add quirk for Cavium Thunder-X2 PCIe erratum #173

On Wed, Feb 21, 2018 at 05:20:40PM -0600, Bjorn Helgaas wrote:
> On Wed, Feb 21, 2018 at 04:25:08PM +0530, George Cherian wrote:
> > I have found another configuration where this fails.
> > Following is the configuration
> > 1) Connected a PCIe Intel i40 card under the root port.
> > 2) unbind the i40 driver and bind with vfio-pci driver.
> > 3) Run lspci in a loop. "lspci -s xx:xx.xx -vvv"
> > 
> > I get the same synchronous external abort.
> > In this case the vfio-pci driver probe it moves the device (i40) to
> > D3hot provided disable_idle_d3 is not set. lspci tries to do
> > the config_access which fails with synchronous external abort when
> > the root port transitions to D3hot.
> 
> It *looks* like rpm_resume() should resume parent devices, i.e., the
> root port, but I don't know that code at all.

It does that unless the ignore_children flag is set, which only few
drivers do.

Sounds to me like another missing pci_config_pm_runtime_get() somewhere
but it's hard to tell without a stacktrace.

Thanks,

Lukas