linux-kernel - Re: [PATCH] driver core: Don't try to create links if they are not needed

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Message-ID: <2c42677c-5e8e-4805-b6a5-0a5baa3e55b5@nvidia.com>
Date: Thu, 3 Oct 2024 11:25:22 +0100
From: Jon Hunter <jonathanh@...dia.com>
To: Saravana Kannan <saravanak@...gle.com>,
 Nícolas F. R. A. Prado <nfraprado@...labora.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J . Wysocki" <rafael@...nel.org>, linux-kernel@...r.kernel.org,
 linux-tegra@...r.kernel.org
Subject: Re: [PATCH] driver core: Don't try to create links if they are not
 needed


On 02/10/2024 21:38, Saravana Kannan wrote:
> On Wed, Oct 2, 2024 at 11:30 AM Jon Hunter <jonathanh@...dia.com> wrote:
>>
>> Hi Greg,
>>
>> On 16/09/2024 18:49, Greg Kroah-Hartman wrote:
>>> On Mon, Sep 16, 2024 at 03:50:34PM +0100, Jon Hunter wrote:
>>>>
>>>> On 11/09/2024 15:32, Greg Kroah-Hartman wrote:
>>>>> On Tue, Sep 10, 2024 at 02:00:19PM +0100, Jon Hunter wrote:
>>>>>> The following error messages are observed on boot with the Tegra234
>>>>>> Jetson AGX Orin board ...
>>>>>>
>>>>>>     tegra-xusb-padctl 3520000.padctl: Failed to create device link (0x180)
>>>>>>       with 1-0008
>>>>>>     tegra-xusb-padctl 3520000.padctl: Failed to create device link (0x180)
>>>>>>       with 1-0008
>>>>>>     tegra-xusb-padctl 3520000.padctl: Failed to create device link (0x180)
>>>>>>       with 1-0008
>>>>>>
>>>>>> In the above case, device_link_add() intentionally returns NULL because
>>>>>> these are SYNC_STATE_ONLY links and the device is already probed.
>>>>>> Therefore, the above messages are not actually errors. Fix this by
>>>>>> replicating the test from device_link_add() in the function
>>>>>> fw_devlink_create_devlink() and don't call device_link_add() if there
>>>>>> are no links to create.
>>>>>>
>>>>>> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
>>>>>
>>>>> What commit id does this fix?
>>>>
>>>>
>>>> Hard to say exactly. The above error message was first added with commit
>>>> 3fb16866b51d ("driver core: fw_devlink: Make cycle detection more robust")
>>>> but at this time we did not have the support in place for Tegra234 USB. I am
>>>> guessing we first started seeing this when I enabled support for the type-c
>>>> controller in commit 16744314ee57 ("arm64: tegra: Populate USB Type-C
>>>> Controller for Jetson AGX Orin"). I can confirm if that is helpful?
>>>>
>>>
>>> That helps, I'll look at this after -rc1 is out, thanks!
>>
>>
>> Let me know if there is anything else I can answer on this one.
> 
> Hi Jon,
> 
> See this.
> https://lore.kernel.org/all/c622df86-0372-450e-b3dd-ab93cd051d6f@notapiano/
> 
> Ignore my point 1. My point 2 still stands. I got busy and forgot to
> reply to Nícolas.
> 
> I'm fine with either one of your patches as long as we define a
> "useless link" function and use it in all the places.


Thanks! Yes I am also fine with Nicolas' fix too. I quite like the 
dev_dbg() in Nicolas' version. I was wondering if we should define a 
function for this check too.

Nicolas do you want to update your patch with a 'useless link' function? 
I will be happy to test on my side. Looks like you identified the exact 
patch that introduced this and have the appropriate fixes tag too.

Thanks
Jon

-- 
nvpublic