Re: [RFT PATCH 2/2] Revert "usb: dwc2: Fix probe problem on bcm2835"

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From	Martin Sperl <kernel@martin.sperl.org>
Newsgroups	linux.kernel
Subject	Re: [RFT PATCH 2/2] Revert "usb: dwc2: Fix probe problem on bcm2835"
Date	Sat, 19 Mar 2016 08:50:02 +0100
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X-Original-Cc	Stefan Wahren <stefan.wahren@i2se.com>, John Youn <John.Youn@synopsys.com>, Doug Anderson <dianders@chromium.org>, Michael Niewoehner <linux@mniewoehner.de>, Tao Huang <huangtao@rock-chips.com>, Julius Werner <jwerner@chromium.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>, Caesar Wang <caesar.upstream@gmail.com>, Heiko Stuebner <heiko@sntech.de>, Felipe Balbi <balbi@kernel.org>, Remi Pommarel <repk@triplefau.lt>
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> On 19.03.2016, at 03:17, Eric Anholt <eric@anholt.net> wrote:
> 
> Stefan Wahren <stefan.wahren@i2se.com> writes:
> 
>> Hi Eric,
>> hi Martin,
>> 
>>> John Youn <John.Youn@synopsys.com> hat am 16. März 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.
> 
Isn’t it possible that this clock (probably BCM2835_CLOCK_VPU) is 
changed by the firmware due to overclocking settings in /boot/config.txt?

Martin

Thread

Re: [RFT PATCH 2/2] Revert "usb: dwc2: Fix probe problem on  bcm2835" Stefan Wahren <stefan.wahren@i2se.com> - 2016-03-19 00:20 +0100
  Re: [RFT PATCH 2/2] Revert "usb: dwc2: Fix probe problem on bcm2835" Eric Anholt <eric@anholt.net> - 2016-03-19 03:20 +0100
    Re: [RFT PATCH 2/2] Revert "usb: dwc2: Fix probe problem on bcm2835" Martin Sperl <kernel@martin.sperl.org> - 2016-03-19 08:50 +0100
      Re: [RFT PATCH 2/2] Revert "usb: dwc2: Fix probe problem on  bcm2835" Stefan Wahren <stefan.wahren@i2se.com> - 2016-03-19 11:00 +0100
        Re: [RFT PATCH 2/2] Revert "usb: dwc2: Fix probe problem on bcm2835" Martin Sperl <kernel@martin.sperl.org> - 2016-03-19 11:20 +0100
          Re: [RFT PATCH 2/2] Revert "usb: dwc2: Fix probe problem on  bcm2835" Stefan Wahren <stefan.wahren@i2se.com> - 2016-03-19 13:20 +0100
    Re: [RFT PATCH 2/2] Revert "usb: dwc2: Fix probe problem on  bcm2835" Stefan Wahren <stefan.wahren@i2se.com> - 2016-03-19 10:50 +0100

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