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Subject: Re: EHCI debug documentation
From: Yinghai Lu <yinghai@kernel.org>
To: Sarah Sharp <sarah.a.sharp@intel.com>, Greg KH <gregkh@suse.de>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Ingo Molnar <mingo@elte.hu>
Cc: linux-usb@vger.kernel.org,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>
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On Tue, Mar 3, 2009 at 3:53 PM, Sarah Sharp <sarah.a.sharp@intel.com> wrote:
> Greetings,
>
> You wrote the EHCI debug port patch for early printk back in July 2008
> (commit 5c05917e7fe313a187ad6ebb94c1c6cf42862a0b). ?Can you add some
> documentation to the Documentation directory about how a Linux user
> would set up a system (cables, files to open to get the printks, etc.)?

please check

==========================================================================================
USB Debug port using Howto

1. HW:

a. target system need to have debug port

00:1d.7 USB Controller: Intel Corporation 82801H (ICH8 Family) USB2
EHCI Controller #1 (rev 03) (prog-if 20 [EHCI])
        Subsystem: Lenovo ThinkPad T61
        Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
ParErr- Stepping- SERR+ FastB2B- DisINTx-
        Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium
>TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 0
        Interrupt: pin D routed to IRQ 19
        Region 0: Memory at fe227000 (32-bit, non-prefetchable) [size=1K]
        Capabilities: [50] Power Management version 2
                Flags: PMEClk- DSI- D1- D2- AuxCurrent=375mA
PME(D0+,D1-,D2-,D3hot+,D3cold+)
                Status: D0 PME-Enable- DSel=0 DScale=0 PME+
        Capabilities: [58] Debug port: BAR=1 offset=00a0
        Kernel driver in use: ehci_hcd
        Kernel modules: ehci-hcd
00: 86 80 36 28 06 01 90 02 03 20 03 0c 00 00 00 00
10: 00 70 22 fe 00 00 00 00 00 00 00 00 00 00 00 00
20: 00 00 00 00 00 00 00 00 00 00 00 00 aa 17 ab 20
30: 00 00 00 00 50 00 00 00 00 00 00 00 0b 04 00 00
40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
50: 01 58 c2 c9 00 80 00 00 0a 00 a0 20 00 00 00 00
60: 20 20 9f 01 00 00 00 00 01 00 00 01 00 00 08 80
70: c0 00 17 3f 00 00 00 00 00 00 00 00 00 00 00 00
80: 00 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00
90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
d0: 00 00 00 00 00 aa ff 00 00 00 00 00 00 00 00 00
e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
f0: 00 00 00 00 88 85 40 00 86 0f 05 00 06 17 02 20

b. netchip USB debug cable

c. console system: have USB port

2. SW setting
a. console system: need to have kernel config
   CONFIG_USB_SERIAL_DEBUG
   you should get /dev/ttyUSBx

   # cat /dev/ttyUSBx could get output

b. target system: need to have kernel config
   CONFIG_EARLY_PRINTK_DBGP

   boot command line: earlyprintk=dbgp

c. for Nvidia Southbridge based system: kernel will try to probe and
find out which port has debug device connected.
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