Re: [RFT PATCH 2/2] Revert "usb: dwc2: Fix probe problem on bcm2835"
From: Martin Sperl
Date: Sat Mar 19 2016 - 06:10:31 EST
> On 19.03.2016, at 10:52, Stefan Wahren <stefan.wahren@xxxxxxxx> wrote:
>
> Hi,
>
>> Martin Sperl <kernel@xxxxxxxxxxxxxxxx> hat am 19. MÃrz 2016 um 08:44
>> geschrieben:
>>
>>
>>
>>> On 19.03.2016, at 03:17, Eric Anholt <eric@xxxxxxxxxx> wrote:
>>>
>>> Stefan Wahren <stefan.wahren@xxxxxxxx> writes:
>>>
>>>> Hi Eric,
>>>> hi Martin,
>>>>
>>>>> John Youn <John.Youn@xxxxxxxxxxxx> hat am 16. MÃrz 2016 um 19:28
>>>>> geschrieben:
>>>>>
>>>>>
>>>>> On 3/10/2016 11:14 AM, John Youn wrote:
>>>>>> On 3/9/2016 11:06 AM, Doug Anderson wrote:
>>>>>>>
>>>>>>> John: it's pretty clear that there's something taking almost exactly
>>>>>>> 10ms on my system and almost exactly 50ms on Stefan's system. Is
>>>>>>> there some register we could poll to see when this process is done?
>>>>>>> ...or can we look at the dwc2 revision number / feature register and
>>>>>>> detect how long to delay?
>>>>>>>
>>
>> Maybe this difference is related to overclocking settings in the firmware?
>>
>>>>>
>>>>> 1. What is the AHB Clock frequency? Is the AHB Clock gated during
>>>>> Reset?
>>>
>>> Low confidence here as I'm tracing lines across a ton of modules, but it
>>> looks like it comes from the USB AXI clock in peri_image, which is a
>>> gate on the normal 250Mhz APB clock, but nothing should be touching that
>>> gate register as part of USB reset as far as I know.
>>>
>> Isnât it possible that this clock (probably BCM2835_CLOCK_VPU) is
>> changed by the firmware due to overclocking settings in /boot/config.txt?
>
> i don't use any overclocking settings.
>
> Are you able to reproduce the behavior on your Pi?
I did not have any problems with USB recently (using 4.5),
so I would not have any idea how to reproduce it.
Note that I am using it with an AXIS USB-ethernet dongle plus USB-stick
all the time on my Compute Module connected via a tiny hub,
so I wonder if that qualifies as being able to trigger the issue...
Martin