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Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability

From Ingo Molnar <mingo@kernel.org>
Newsgroups linux.kernel
Subject Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability
Date 2017-01-26 08:30 +0100
Message-ID <t3MFj-4sB-7@gated-at.bofh.it> (permalink)
References (5 earlier) <t3s3U-8nC-19@gated-at.bofh.it> <t3swW-6x-23@gated-at.bofh.it> <t3uS6-1Hz-15@gated-at.bofh.it> <t3wTT-2VB-9@gated-at.bofh.it> <t3y9k-3Do-25@gated-at.bofh.it>
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* Lu Baolu <baolu.lu@linux.intel.com> wrote:

> 
> Hi,
> 
> On 01/25/2017 10:38 PM, Peter Zijlstra wrote:
> > On Wed, Jan 25, 2017 at 08:27:38PM +0800, Lu Baolu wrote:
> >> In my driver, udelay() is mostly used to handle time out.
> >>
> >> Xdbc hides most USB things in its firmware. Early printk driver only needs
> >> to setup the registers/data structures and wait until link ready or time out.
> >> Without udelay(), I have no means to convert the polling times into waiting
> >> time.
> > What is timeout and why?
> 
> Put it in simple:
> 
> The driver sets the RUN bit in control register and polls READY
> bit in status register for the successful USB device enumeration.
> As the USB device enumeration might fail and the READY bit will
> never be set, the driver must have a timeout logic to avoid
> endless loop.

Is there any error status available in the host registers anywhere that tells us 
that enumeration did not succeed?

Thanks,

	Ingo

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Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Ingo Molnar <mingo@kernel.org> - 2017-01-19 10:50 +0100
  Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Lu Baolu <baolu.lu@linux.intel.com> - 2017-01-20 03:50 +0100
    Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Ingo Molnar <mingo@kernel.org> - 2017-01-22 10:10 +0100
      Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Lu Baolu <baolu.lu@linux.intel.com> - 2017-01-24 05:50 +0100
        Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Ingo Molnar <mingo@kernel.org> - 2017-01-24 09:30 +0100
          Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Lu Baolu <baolu.lu@linux.intel.com> - 2017-01-25 06:30 +0100
            Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Ingo Molnar <mingo@kernel.org> - 2017-01-25 10:30 +0100
              Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Peter Zijlstra <peterz@infradead.org> - 2017-01-25 11:00 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Lu Baolu <baolu.lu@linux.intel.com> - 2017-01-25 13:30 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Peter Zijlstra <peterz@infradead.org> - 2017-01-25 15:40 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Lu Baolu <baolu.lu@linux.intel.com> - 2017-01-25 17:00 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Peter Zijlstra <peterz@infradead.org> - 2017-01-25 17:20 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Lu Baolu <baolu.lu@linux.intel.com> - 2017-01-26 04:40 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Ingo Molnar <mingo@kernel.org> - 2017-01-26 08:20 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Lu Baolu <baolu.lu@linux.intel.com> - 2017-01-26 08:50 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Ingo Molnar <mingo@kernel.org> - 2017-01-26 09:20 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Peter Zijlstra <peterz@infradead.org> - 2017-01-26 11:30 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Ingo Molnar <mingo@kernel.org> - 2017-01-26 17:10 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Peter Zijlstra <peterz@infradead.org> - 2017-01-26 18:50 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Ingo Molnar <mingo@kernel.org> - 2017-01-27 08:00 +0100
                Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Ingo Molnar <mingo@kernel.org> - 2017-01-26 08:30 +0100
              Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Lu Baolu <baolu.lu@linux.intel.com> - 2017-01-25 13:20 +0100
              Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Lu Baolu <baolu.lu@linux.intel.com> - 2017-01-26 04:30 +0100

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