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

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Message-ID: <CAGETcx8E9FddpwMO4+oqeEc0RVMLbUOs2m+=B900xzrLvEkSXw@mail.gmail.com>
Date: Wed, 2 Oct 2024 13:38:23 -0700
From: Saravana Kannan <saravanak@...gle.com>
To: Jon Hunter <jonathanh@...dia.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 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,
Saravana