[U-Boot] A20-olinuxino-micro hangs in U-boot if powered from MINI-USB only.

[U-Boot] A20-olinuxino-micro hangs in U-boot if powered from MINI-USB only.

[Nikolai Zhubr]

Hi all,

I'm observing that the said A20-onlinuxino-micro board hangs in U-boot 
in probing USB2 (see example below) in case it is powered by connecting 
its mini-usb connector to a computer. The problem does not happen if 12V 
power connector is also empoyed. (Note: the example attached below is 
for RC1, but RC2 is no different)
I can't say if such problem was also present in previous version of 
u-boot or not.


Thank you,

Regards,
Nikolai

U-Boot 2019.01-rc1 (Dec 13 2018 - 15:11:11 +0300) Allwinner Technology

CPU:   Allwinner A20 (SUN7I)
Model: Olimex A20-Olinuxino Micro
I2C:   ready
DRAM:  1 GiB
MMC:   SUNXI SD/MMC: 0, SUNXI SD/MMC: 1
Loading Environment from FAT... MMC: no card present
In:    serial
Out:   serial
Err:   serial
Net:   eth0: ethernet at 1c50000
starting USB...
USB0:   USB EHCI 1.00
USB1:   USB OHCI 1.0
USB2:

[U-Boot] [linux-sunxi] A20-olinuxino-micro hangs in U-boot if powered from MINI-USB only.

[Diego Roversi]

On Mon, 24 Dec 2018 01:04:04 +0300
Nikolai Zhubr <n-a-zhubr@yandex.ru> wrote:

> Hi all,
> 
> I'm observing that the said A20-onlinuxino-micro board hangs in U-boot 
> in probing USB2 (see example below) in case it is powered by connecting 

I think it's normal. During the boot, u-boot initialize the usb otg, and for a fraction of second the power is disconnected. I solved it by attaching a battery (and I have a PSU as a side effect :) ).

Regards,
  Diego.

-- 
Diego Roversi <diegor@tiscali.it>

[U-Boot] [linux-sunxi] A20-olinuxino-micro hangs in U-boot if powered from MINI-USB only.

[Nikolai Zhubr]

Hi,
24.12.2018 20:32, Diego Roversi:
>> I'm observing that the said A20-onlinuxino-micro board hangs in U-boot
>> in probing USB2 (see example below) in case it is powered by connecting
>
> I think it's normal. During the boot, u-boot initialize the usb otg, and for a fraction of second the power is disconnected. I solved it by attaching a battery (and I have a PSU as a side effect :) ).

Ah, got it. Thats a funny issue then. Its not the software to blame. Ok.
(Ideally, this peculiarity should probably have been mentioned by Olimex 
in their docs, but maybe I've overlooked it.)
Solved it for now by disabling USB altogether.


Thank you,

Regards,
Nikolai

>
> Regards,
>    Diego.
>

[U-Boot] [linux-sunxi] A20-olinuxino-micro hangs in U-boot if powered from MINI-USB only.

[John S]

On Monday, 24 December 2018, 19:10:24 GMT, Nikolai Zhubr <n-a-zhubr@yandex.ru> wrote: 
>>Hi,24.12.2018 20:32, Diego Roversi:
>>> I'm observing that the said A20-onlinuxino-micro board hangs in U-boot
>> in probing USB2 (see example below) in case it is powered by connecting
>>
>> I think it's normal. During the boot, u-boot initialize the usb otg, and for a
>> fraction of second the power is disconnected. I solved it by attaching a
>> battery (and I have a PSU as a side effect :) ).

> Ah, got it. Thats a funny issue then. Its not the software to blame. Ok.
> (Ideally, this peculiarity should probably have been mentioned by Olimex
> in their docs, but maybe I've overlooked it.)
> Solved it for now by disabling USB altogether.

Isn't it caused by the software as stated above, i.e. nothing to do with Olimex?

John

[U-Boot] [linux-sunxi] A20-olinuxino-micro hangs in U-boot if powered from MINI-USB only.

[Nikolai Zhubr]

Hi,
24.12.2018 22:54, John S:
> On Monday, 24 December 2018, 19:10:24 GMT, Nikolai Zhubr<n-a-zhubr@yandex.ru>  wrote:
>>> Hi,24.12.2018 20:32, Diego Roversi:
>>>> I'm observing that the said A20-onlinuxino-micro board hangs in U-boot
>>> in probing USB2 (see example below) in case it is powered by connecting
>>>
>>> I think it's normal. During the boot, u-boot initialize the usb otg, and for a
>>> fraction of second the power is disconnected. I solved it by attaching a
>>> battery (and I have a PSU as a side effect :) ).
>
>> Ah, got it. Thats a funny issue then. Its not the software to blame. Ok.
>> (Ideally, this peculiarity should probably have been mentioned by Olimex
>> in their docs, but maybe I've overlooked it.)
>> Solved it for now by disabling USB altogether.
>
> Isn't it caused by the software as stated above, i.e. nothing to do with Olimex?

Well, IMHO is has to do with Olimex because they designed this specific 
circuitry, and the circuitry is such that 5V voltage constantly applied 
to the micro-usb connector might essentially become disconnected (at the 
board side) by programming -- if I understood it correctly. I suppose 
this certainly could be prevented in hardware, by e.g. just wiring the 
5V usb line to a power unit through a diode, whatever, unless it is 
prohibited by some sort of usb compatability requirements. I don't know 
if it would be good though. Of course the effect is caused by software 
in some sence, but the software can not know that there is no other 
power supply line present when it probes this usb port? Or could it 
indeed? I'm not sure if AXP state could be somehow probed to do a 
workaround, in theory, but that would be an extreme overcomplication anyway.


Thank you,

Regards,
Nikolai



>
> John
>

[U-Boot] [linux-sunxi] A20-olinuxino-micro hangs in U-boot if powered from MINI-USB only.

[John S]

On Monday, 24 December 2018, 21:37:01 GMT, Nikolai Zhubr <n-a-zhubr@yandex.ru> wrote: 
>>24.12.2018 22:54, John S:
>> Isn't it caused by the software as stated above, i.e. nothing to do with
>> Olimex?
> Well, IMHO is has to do with Olimex because they designed this specific
> circuitry, and the circuitry is such that 5V voltage constantly applied
> to the micro-usb connector might essentially become disconnected (at the
> board side) by programming -- if I understood it correctly.

The software needs to be responsible for its own actions.

Does the problem you reported occur with the Olimex image(s)?  If so it may be wise to report it to Olimex.

If not, which commit or change caused it?

BTW I read in the Olimex documentation that best practice is to power it differently than the way you mention.

John

[U-Boot] [linux-sunxi] A20-olinuxino-micro hangs in U-boot if powered from MINI-USB only.

[Nikolai Zhubr]

Hi,

27.12.2018 23:48, 'John S' via linux-sunxi:
>> Well, IMHO is has to do with Olimex because they designed this specific
>> circuitry, and the circuitry is such that 5V voltage constantly applied
>> to the micro-usb connector might essentially become disconnected (at the
>> board side) by programming -- if I understood it correctly.
>
> The software needs to be responsible for its own actions.

Sure, ideally. That's why I reported.

> Does the problem you reported occur with the Olimex image(s)?  If so it may be wise to report it to Olimex.

I can't say about Olimex images at the moment because I switched to more 
current (alternative) images and subsequently to mainline openwrt and 
the board is already mounted for intended operation. Maybe I do some 
experiments later. I'd like to clarify, I don't blame Olimex, they are 
nice. Keeping close to mainline is not always easy.

> If not, which commit or change caused it?

Again, I can't say at the moment. Not even sure if it could be fixed on 
the software side.

> BTW I read in the Olimex documentation that best practice is to power it differently than the way you mention.

Yes, that is true.
But powering through mini-usb is so wonderfully handy!


Thank you,

Regards,
Nikolai

> John
>