MUSB dual-role on AM335x behaving weirdly

[Bin Liu]

Alexandre,

On Thu, May 14, 2015 at 4:26 PM, Alexandre Belloni
<alexandre.belloni at free-electrons.com> wrote:
> On 14/05/2015 at 16:16:12 -0500, Bin Liu wrote :
>> I think I found the root cause of the problem: board design issue - I
>> bet the custom board has too much cap on VBUS line. It should be <
>> 10uF.
>>
>
> We have a custom board that exhibits the issue but it only has a 100nF
> cap on VBUS.

Have you measured the VBUS discharging? Is there any way to share your
schematics?

Regards,
-Bin.

>
>> I just noticed I have the Jumper 36 on on my EVM, which adds 154.7uF
>> cap on VBUS causing discharge takes ~20sec. After removed the jumper,
>> which leaves only 4.7uF cap on VBUS, now it only takes ~0.4sec to
>> generate Disconnect IRQ. Here is the log.
>>
>> root@:~# [ 2504.893123] musb-hdrc musb-hdrc.0.auto: usbintr (1) epintr(0)
>> [ 2504.899198] musb-hdrc musb-hdrc.0.auto: <== DevCtl=99, int_usb=0x1
>> [ 2504.912751] zero gadget: suspend
>> [ 2504.916145] zero gadget: zero_suspend
>> [ 2505.303937] musb-hdrc musb-hdrc.0.auto: usbintr (20) epintr(0)
>> [ 2505.310072] musb-hdrc musb-hdrc.0.auto: <== DevCtl=88, int_usb=0x20
>> [ 2505.325355] zero gadget: reset config
>> [ 2507.303288] musb-hdrc musb-hdrc.0.auto: Poll devctl 80 (b_idle)
>>
>
> --
> Alexandre Belloni, Free Electrons
> Embedded Linux, Kernel and Android engineering
> http://free-electrons.com