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From: Ingo Molnar <mingo@kernel.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Mathias Nyman <mathias.nyman@linux.intel.com>,
	Ingo Molnar <mingo@redhat.com>,
	tglx@linutronix.de, linux-usb@vger.kernel.org, x86@kernel.org,
	linux-kernel@vger.kernel.org, Jiri Slaby <jslaby@suse.cz>
Subject: Re: [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability
Date: Thu, 26 Jan 2017 08:22:19 +0100	[thread overview]
Message-ID: <20170126072219.GB3399@gmail.com> (raw)
In-Reply-To: <5888C986.4020809@linux.intel.com>


* 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

  parent reply	other threads:[~2017-01-26  7:22 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-11-15  6:02 [PATCH v5 0/4] usb: early: add support for early printk through USB3 debug port Lu Baolu
2016-11-15  6:02 ` [PATCH v5 1/4] usb: dbc: early driver for xhci debug capability Lu Baolu
2017-01-19  9:37   ` Ingo Molnar
2017-01-20  2:47     ` Lu Baolu
2017-01-22  9:04       ` Ingo Molnar
2017-01-24  4:44         ` Lu Baolu
2017-01-24  8:20           ` Ingo Molnar
2017-01-25  5:28             ` Lu Baolu
2017-01-25  9:23               ` Ingo Molnar
2017-01-25  9:57                 ` Peter Zijlstra
2017-01-25 12:27                   ` Lu Baolu
2017-01-25 14:38                     ` Peter Zijlstra
2017-01-25 15:51                       ` Lu Baolu
2017-01-25 16:16                         ` Peter Zijlstra
2017-01-26  3:37                           ` Lu Baolu
2017-01-26  7:19                             ` Ingo Molnar
2017-01-26  7:49                               ` Lu Baolu
2017-01-26  8:17                                 ` Ingo Molnar
2017-01-26 10:28                               ` Peter Zijlstra
2017-01-26 16:01                                 ` Ingo Molnar
2017-01-26 17:39                                   ` Peter Zijlstra
2017-01-27  6:51                                     ` Ingo Molnar
2017-02-09  5:59                               ` Lu Baolu
2017-01-26  7:22                         ` Ingo Molnar [this message]
2017-02-09  7:37                           ` Lu Baolu
2017-01-25 12:17                 ` Lu Baolu
2017-01-26  3:26                 ` Lu Baolu
2016-11-15  6:02 ` [PATCH v5 2/4] x86: add support for earlyprintk via USB3 debug port Lu Baolu
2017-01-19  9:38   ` Ingo Molnar
2017-01-20  2:48     ` Lu Baolu
2016-11-15  6:02 ` [PATCH v5 3/4] usb: serial: usb_debug: add support for dbc debug device Lu Baolu
2017-01-19  9:39   ` Ingo Molnar
2017-01-20  2:50     ` Lu Baolu
2016-11-15  6:02 ` [PATCH v5 4/4] usb: doc: add document for USB3 debug port usage Lu Baolu
2017-01-19  9:41   ` Ingo Molnar
2017-01-20  2:53     ` Lu Baolu
2017-01-18  6:20 ` [PATCH v5 0/4] usb: early: add support for early printk through USB3 debug port Lu Baolu
2017-01-19  9:06   ` Greg Kroah-Hartman
2017-01-19  9:09     ` Ingo Molnar
2017-01-19 11:24       ` Mathias Nyman
2017-01-19  9:12 ` Ingo Molnar
2017-01-20  2:56   ` Lu Baolu

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