Bug#810894: src:linux: GPIO probe failure on Linkstation LS-WXL/WSXL

[Roger Shimizu <rogershimizu@gmail.com>]

Thanks for your feedback, Uwe!

On Thu, Jan 14, 2016 at 4:19 AM, Uwe Kleine-König
<uwe+debian@kleine-koenig.org> wrote:
> Hello Roger,
>
> On 01/13/2016 02:11 PM, Roger Shimizu wrote:
>> Package: src:linux
>> Version: 3.16.7-ckt20-1+deb8u1
>> Severity: normal
>> Control: notfound -1 3.16.7-ckt4-3
>> Control: found -1 3.16.7-ckt7-1
>> Control: found -1 3.16.7-ckt20-1+deb8u1
>> Control: notfound -1 4.2.6-3~bpo8+2
>> Control: notfound -1 4.3.3-5~bpo8+1
>> Control: notfound -1 4.4~rc8-1~exp1
>>
>> I need to run the following command to enable USB port on Linkstation
>> LS-WXL/WSXL (armel/kirkwood with DTS [0] ):
>>   echo 37 >/sys/class/gpio/export
>>   echo out > /sys/class/gpio/gpio37/direction
>>   echo 1 > /sys/class/gpio/gpio37/value
>
> Side note: you can shorten that to:
>
>         echo 37 > /sys/class/gpio/export
>         echo high > /sys/class/gpio/gpio37/direction

Learned new tips. Thank you!

>> The 3-line script runs well on Jessie rootfs + kernel listed below:
>> - 3.16.7-ckt4-3
>> - 4.2.6-3~bpo8+2
>> - 4.4~rc8-1~exp1
>> But fails from 3.16.7-ckt7-1 to 3.16.7-ckt20-1+deb8u1 (latest jessie kernel).
>>
>> The error message is like this:
>> # echo 37 >/sys/class/gpio/export
>> -bash: echo: write error: Device or resource busy
>
> Looking at the device tree I'd say it's correct that the gpio cannot be
> controlled from user space because it's used to enable usb.

I don't understand why it's not able to control the gpio.
Could you please explain in detail?

I'm the upstream contributor for this DTS.
I know there may be something wrong with the gpio part, but I don't
know how to know which part is not working.

> A quick look at the provided dmesg for 3.16.7-ckt7-1 makes me expect
> that usb works there without the gpio commands above? If so there is no
> bug, right?

Yes, dmesg shows USB is recognized. But actually it's not working
until user land's gpio export and setting.
If gpio export fails, the USB won't work at all.
I guess the gpio pin is to set whether to give USB power.

Cheers,
Roger