Subject: Re: [PATCH] ARM: mvebu_v7_defconfig: fix Ethernet on Clearfog

From: Gregory CLEMENT <[email-masked]>
Date: Tue, 11 Jun 2019 17:04:38 +0200

Hello Russell King,

> On Tue, Jun 11, 2019 at 01:28:32PM +0200, Gregory CLEMENT wrote:
>> Jan Kundrát <[email-masked]> writes:
>> 
>> > On sobota 18. května 2019 0:50:28 CEST, Jan Kundrát wrote:
>> >>> Well, this is just about configuration, I don't consider this is
>> >>> something that is a candidate for a fix.
>> >>> 
>> >>> If there is a regression, then, it is maybe located in the Kconfig
>> >>> dependency.
>> >>> 
>> >>> Of course I can change my mind with good arguments :)
>> >>
>> >> Hi Gregory,
>> >> I agree that it's just a config bug, but it's also something 
>> >> which can silently produce broken systems. If this is not fixed, 
>> >> people building their 5.2 kernels will not have working network 
>> >> on Clearfog unless they take an extra action. For example, a 
>> >> Buildroot defconfig that's been available for quite some time 
>> >> (and which uses just `mvebu_v7_defconfig` for kernel) suddenly 
>> >> becomes broken.
>> >>
>> >> Isn't the whole point of the -rc release to find *and* fix bugs 
>> >> early? This trivial patch does not introduce any new or untested 
>> >> code. I made a choice to test a pre-release kernel, I hit a bug 
>> >> -- no big deal. I found the root cause, I sent a trivial fix 
>> >> upstream, and now I'm told by a maintainer that they will let 
>> >> the next kernel version, which is about seven -rc releases away, 
>> >> be released without a fully functioning network, I am surprised 
>> >> by that. I would have understood this better if we were at the 
>> >> final -rc stage, but during the merge window? Or is that perhaps 
>> >> a misunderstanding and you're planning to send this in time 
>> >> after -rc1?
>> >
>> > Hi Gregory,
>> > was I successful in persuading you that this patch should be included in 
>> > the 5.2 tree, so that Clearfog Base has all three Ethernet interfaces?
>> 
>> Finally I moved the commit from mvebu/arm to mvebu/fixes. I still think
>> the problem is at driver level, but I didn't take enough time to find
>> where and we didn't have any feedback from the author of the initila
>> patch.
>
> I don't see that there's much that I need to say, and I'm at a total
> loss to work out why you think it's a problem at driver level.
>
> Why do you think it's appropriate for mvneta to know whether the a38x
> comphy driver is configured for the current kernel or not, given that
> mvneta is not exclusively used on Armada 38x systems?
>
> We're already doing the best we can do with ignoring the comphy if
> not present; the only case that we defer probe is when
> devm_of_phy_get() returns -EPROBE_DEFER, which could mean "the comphy
> driver is a module but is not loaded yet" or "the comphy driver has
> not been probed yet" - we can't ignore those.
>
>> So let's try to push it to fixes, I will do the pull request for arm-soc
>> before end of the week.
>
> That's the correct solution, and it should also have a Fixes: tag on
> it.  Unfortunately, keeping the defconfigs up to date is quite a hard
> problem unless you have lots of computing power to build and boot all
> the defconfigs on all platforms (I don't.)

Thanks for the explanation and confirmation. As the issue appeared only
in 5.2-rc1 then it won't be backported and for my point of view the main
interest of Fixes is for the backport, that's I though that not having a
Fixes tag was an issue.

But I don't mind adding a Fixes: tag.

Jan, do you find which exact commit cause this regression?

Thanks,

Gregory

>
> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
> According to speedtest.net: 11.9Mbps down 500kbps up

-- 
Gregory Clement, Bootlin
Embedded Linux and Kernel engineering
http://bootlin.com

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