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

From: Tal Gilboa <talgi@mellanox.com>
To: "Alex G." <mr.nuke.me@gmail.com>, Bjorn Helgaas <helgaas@kernel.org>
Cc: bhelgaas@google.com, alex_gagniuc@dellteam.com,
	austin_bolen@dell.com, shyam_iyer@dell.com,
	keith.busch@intel.com, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
	Ariel Elior <ariel.elior@cavium.com>,
	Michael Chan <michael.chan@broadcom.com>,
	Ganesh Goudar <ganeshgr@chelsio.com>,
	Tariq Toukan <tariqt@mellanox.com>,
	Jakub Kicinski <jakub.kicinski@netronome.com>,
	Dave Airlie <airlied@gmail.com>,
	Alex Deucher <alexander.deucher@amd.com>
Subject: Re: [PATCH v3] PCI: Check for PCIe downtraining conditions
Date: Tue, 24 Jul 2018 00:35:39 +0300	[thread overview]
Message-ID: <d7da53d3-1631-7d3f-5b78-15a8af30a759@mellanox.com> (raw)
In-Reply-To: <757729fb-1eb5-e1fa-899b-5cef0cc3106c@gmail.com>

On 7/23/2018 8:01 PM, Alex G. wrote:
> On 07/23/2018 12:21 AM, Tal Gilboa wrote:
>> On 7/19/2018 6:49 PM, Alex G. wrote:
>>>
>>>
>>> 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
>>
>> That's the point - we don't want to call pcie_print_link_status() for 
>> virtual functions. We make the distinction in our driver. If you want 
>> to change the code to call this function by default it shouldn't 
>> affect the current usage.
> 
> I'm not understanding very well what you're asking. I understand you 
> want to avoid printing this message on virtual functions, and that's 
> already taken care of. I'm also not changing current behavior.  Let's 
> get v2 out and start the discussion again based on that.
> 
> Alex

Oh ok I see. In this case, please remove the explicit call in mlx4/5 
drivers so it won't be duplicated.