Re: musb is broken in master

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 2/18/20 12:19 PM, Yegor Yefremov wrote:
> Hello Ahmad,
> 
> On Tue, Feb 18, 2020 at 11:57 AM Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
>>
>> Hello Yegor,
>>
>> On 2/18/20 10:58 AM, Yegor Yefremov wrote:
>>> I have bisected the musb driver on am335x (baltos system
>>> arch/arm/dts/am335x-baltos-minimal.dts) from v2019.11.0 and this is
>>> the result:
>>>
>>> 574eed3f6fcf056aa4c9e46c4b5224e3f7844d8d is the first bad commit
>>> commit 574eed3f6fcf056aa4c9e46c4b5224e3f7844d8d
>>> Author: Sascha Hauer <s.hauer@pengutronix.de>
>>> Date:   Thu Dec 19 05:46:54 2019 +0100
>>>
>>>     dts: update to v5.5-rc1
>>>
>>>     Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
>>>
>>> :040000 040000 4f6416a5af14d6328ef2c8ac46d9ac4a17a37404
>>> 525e33dda1e735ef2f633f4d99c501ba938a7263 M      dts
>>>
>>> I need only the host functionality to mount a USB drive. My defconfig
>>> can be found here [1].
>>>
>>> Any idea what could have happened?
>>
>> git log v5.4..v5.5-rc1 arch/arm/boot/dts/am335x*.dtsi
>> gives me kernel commit 12afc0cf81 ("ARM: dts: Drop pointless status changing for am3 musb").
>> Does reverting it fix the issue for you?
> 
> Yes, it does. Though the revert result is a little bit ugly i.e. at
> least one conflict.

yes, it's not meant as permanent solution.
Which status = "okay" is the one that 'fixes' it?
 
> But when I start the kernel 5.6-rc2 that already incorporates these
> DTS changes, I have no problems with USB. So far only the barebox is
> affected by this change.

Possibly a device driver in barebox for the now-disabled peripheral
turns on a clock, enables a regulator, toggles a reset or initializes
some register that also affects the USB working at all.

Best course of action would be to check which driver it is, check whether
Linux uses it, comment out stuff to find what the magic sauce is that
the driver does and add that to the driver that misses it.

(sometimes it's just that the device tree binding changed. In that case,
you can either patch in a missing property in arch/arm/dts or patch
barebox drivers to accept the new binding as well)

Cheers
Ahmad

> 
> Cheers,
> Yegor
> 


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