linux-kernel - Re: [PATCH v3] PCI: Check for PCIe downtraining conditions

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Date:   Thu, 19 Jul 2018 10:49:55 -0500
From:   "Alex G." <mr.nuke.me@...il.com>
To:     Tal Gilboa <talgi@...lanox.com>, Bjorn Helgaas <helgaas@...nel.org>
Cc:     bhelgaas@...gle.com, alex_gagniuc@...lteam.com,
        austin_bolen@...l.com, shyam_iyer@...l.com, keith.busch@...el.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Ariel Elior <ariel.elior@...ium.com>,
        Michael Chan <michael.chan@...adcom.com>,
        Ganesh Goudar <ganeshgr@...lsio.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Dave Airlie <airlied@...il.com>,
        Alex Deucher <alexander.deucher@....com>
Subject: Re: [PATCH v3] PCI: Check for PCIe downtraining conditions



On 07/18/2018 08:38 AM, Tal Gilboa wrote:
> On 7/16/2018 5:17 PM, Bjorn Helgaas wrote:
>> [+cc maintainers of drivers that already use pcie_print_link_status()
>> and GPU folks]
[snip]
>>
>>> +    /* Multi-function PCIe share the same link/status. */
>>> +    if ((PCI_FUNC(dev->devfn) != 0) || dev->is_virtfn)
>>> +        return;
>>> +
>>> +    pcie_print_link_status(dev);
>>> +}
> 
> Is this function called by default for every PCIe device? What about 
> VFs? We make an exception for them on our driver since a VF doesn't have 
> access to the needed information in order to provide a meaningful message.

I'm assuming VF means virtual function. pcie_print_link_status() doesn't 
care if it's passed a virtual function. It will try to do its job. 
That's why I bail out three lines above, with 'dev->is_virtfn' check.

Alex