[Letux-kernel] Ethernet interface on Beaglebone Black broken since 5.15.0-rc1-letux+

[H. Nikolaus Schaller]

Hi Jean Rene,

> Am 24.09.2021 um 00:06 schrieb Jean Rene Dawin <jdawin at math.uni-bielefeld.de>:
> 
> Hi,
> 
> since 5.15.0-rc1-letux+ the ethernet interface on Beaglebone Black no
> longer works.

I think I briefly tried but I am not sure if it was -rc2.

> 
> In the boot messages for 5.14.6-letux+ there is
> 
> [    0.867514] random: fast init done
> [    0.867704] random: crng init done
> [    0.956608] davinci_mdio 4a101000.mdio: davinci mdio revision 1.6, bus freq 1000000
> [    0.956721] libphy: 4a101000.mdio: probed
> [    0.958786] davinci_mdio 4a101000.mdio: phy[0]: device 4a101000.mdio:00, driver SMSC LAN8710/LAN8720
> [    0.959188] cpsw 4a100000.ethernet: initialized cpsw ale version 1.4
> [    0.959234] cpsw 4a100000.ethernet: ALE Table size 1024
> [    0.959389] cpsw 4a100000.ethernet: Detected MACID = 54:4a:16:bb:86:e9
> [    0.974126] am335x-bandgap 44e10448.bandgap: hwmon_device_register() is deprecated. Please convert the driver to use hwmon_device_register_with_info().
> 
> but with 5.15.0-rc1-letux+ there is just
> 
> [    0.725388] random: fast init done
> [    0.729446] random: crng init done
> [    0.768411] am335x-bandgap 44e10448.bandgap: hwmon_device_register() is deprecated. Please convert the driver to use hwmon_device_register_with_info().

this is fixed in 5.15-rc2.

> 
> and the interface is not present after boot.
> 
> I would like to bisect the issue but I'm not sure how.
> If I do for example
> 
> git bisect good a47fe0df52b98d2eb381ce282ba0208fed446acd
> git bisect bad dd2caf156ef189647af40d92a587d4c59a2f8442
> 
> it says
> 
> Bisecting: a merge base must be tested
> [7d2a07b769330c34b4deabeed939325c77a7ec2f] Linux 5.14
> 
> But 7d2a07b769330c34b4deabeed939325c77a7ec2f is the upstream Linux
> commit without the letux-patches, right?
> 
> What would be the best way to find the commit which caused the issue?

Well, bisecting Letux is a nightmare and there is no simple answer.

The problem is that there is
v5.14.0 + letux
...
v5.15-rc1 + letux

And the +letux is not even identical since rebasing to v5.15-rc1 involves some conflict resolutions or code adaptations.

The result is in any case that v5.14.0 + letux is not a direct ancestor of v5.15-rc1 + letux and bisect finds another one. This does not include any Letux feature branches.

In theory it would be possible to

git checkout letux-5.15-rc1
git rebase letux-5.14

The result should be a "migration path" which can be bisected.

But this rebases tenthousands of commits and some need manual conflict resolution. And I have not found a way to automate.

So my strategy is usually to check git diff --stat of relevant subsystems and try to understand what has changed.

BR,
Nikolaus