Hi, On 10/20/2016 04:30 PM, Jani Nikula wrote: > On Thu, 20 Oct 2016, Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote: >> Hi Jani, >> >> On 10/19/2016 03:48 PM, Jani Nikula wrote: >>> On Wed, 19 Oct 2016, Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote: >>>> Add Documentation/usb/usb3-debug-port.txt. This document includes >>>> the user guide for USB3 debug port. >>> If you're adding completely new files, please at least consider writing >>> them in reStructuredText, so we can easily bolt them to the Sphinx >>> build. Just a few tweaks would be required, comments inline below. >> Thanks for your comments. I will refactor my document according >> to your comments. >> >> By the way, are there any tools that I can use to check the document >> format? > Read Documentation/kernel-documentation.rxt. Install Sphinx. Run 'make > htmldocs'. Got it. Thank you. Best regards, Lu Baolu > > BR, > Jani. > > >> Best regards, >> Lu Baolu >> >>> BR, >>> Jani. >>> >>>> Cc: linux-doc@xxxxxxxxxxxxxxx >>>> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> >>>> --- >>>> Documentation/usb/usb3-debug-port.txt | 87 +++++++++++++++++++++++++++++++++++ >>>> 1 file changed, 87 insertions(+) >>>> create mode 100644 Documentation/usb/usb3-debug-port.txt >>>> >>>> diff --git a/Documentation/usb/usb3-debug-port.txt b/Documentation/usb/usb3-debug-port.txt >>>> new file mode 100644 >>>> index 0000000..df5ce27 >>>> --- /dev/null >>>> +++ b/Documentation/usb/usb3-debug-port.txt >>>> @@ -0,0 +1,87 @@ >>>> + USB3 debug port >>> Make that a title with >>> >>> =============== >>> USB3 debug port >>> =============== >>> >>>> + >>>> + Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> >>> :Author: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> >>> >>> Although git blame will give a more accurate idea after the file's been >>> edited by others. >>> >>>> + >>>> + Last-updated: October 2016 >>> :Date: October 2016 >>> >>> Again, this is what git does. >>> >>>> + >>>> +GENERAL >>>> +======= >>>> + >>>> +This is a HOWTO for using USB3 debug port on x86 systems. >>>> + >>>> +Before using any kernel debugging functionalities based on USB3 >>>> +debug port, you need to check 1) whether debug port is supported >>>> +by the xHCI host, 2) which port is used for debugging purpose >>>> +(normally the first USB3 root port). You must have a USB 3.0 >>>> +super-speed A-to-A debugging cable to connect the debug target >>>> +with a debug host. In this document, a debug target stands for >>>> +the system under debugging; while, a debug host stands for a >>>> +stand-alone system that is able to talk to the debugging target >>>> +through the USB3 debug port. >>>> + >>>> +EARLY PRINTK >>>> +============ >>>> + >>>> +On debug target system, you need to customize a debugging kernel >>>> +with CONFIG_EARLY_PRINTK_XDBC enabled. And add below kernel boot >>>> +parameter. >>> Add :: at the end of previous line to make the below indented block >>> preformatted text. Ditto for the others. >>> >>>> + >>>> + "earlyprintk=xdbc" >>>> + >>>> +If there are multiple xHCI controllers in the system, you can >>>> +append a host contoller index to this kernel parameter. This >>>> +index is started from 0. >>>> + >>>> +If you are going to leverage the keep option defined by the >>>> +early printk framework to keep the boot console alive after >>>> +early boot, you'd better add below kernel boot parameter. >>>> + >>>> + "usbcore.autosuspend=-1" >>>> + >>>> +On debug host side, you don't need to customize the kernel, but >>>> +you need to disable usb subsystem runtime power management by >>>> +adding below kernel boot parameter. >>>> + >>>> + "usbcore.autosuspend=-1" >>>> + >>>> +Before starting the debug target, you should connect the debug >>>> +port on debug target with a root port or port of any external hub >>>> +on the debug host. The cable used to connect these two ports >>>> +should be a USB 3.0 super-speed A-to-A debugging cable. >>>> + >>>> +During early boot of debug target, DbC (the debug engine for USB3 >>>> +debug port) hardware gets initialized. Debug host should be able >>>> +to enumerate the debug target as a debug device. Debug host will >>>> +then bind the debug device with the usb_debug driver module and >>>> +create the /dev/ttyUSB0 device. >>>> + >>>> +If device enumeration goes smoothly, you should be able to see >>>> +below kernel messages on debug host. >>> Again, add :: and indent the below lines by some spaces. >>> >>>> + >>>> +# tail -f /var/log/kern.log >>>> + >>>> +[ 1815.983374] usb 4-3: new SuperSpeed USB device number 4 using xhci_hcd >>>> +[ 1815.999595] usb 4-3: LPM exit latency is zeroed, disabling LPM. >>>> +[ 1815.999899] usb 4-3: New USB device found, idVendor=1d6b, idProduct=0004 >>>> +[ 1815.999902] usb 4-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3 >>>> +[ 1815.999903] usb 4-3: Product: Remote GDB >>>> +[ 1815.999904] usb 4-3: Manufacturer: Linux >>>> +[ 1815.999905] usb 4-3: SerialNumber: 0001 >>>> +[ 1816.000240] usb_debug 4-3:1.0: xhci_dbc converter detected >>>> +[ 1816.000360] usb 4-3: xhci_dbc converter now attached to ttyUSB0 >>>> + >>>> +You can run below bash scripts on debug host to read the kernel >>>> +log sent from debug target. >>> Same here. Alternatively, if you do >>> >>> .. code-block:: sh >>> >>> and indent the block, you'll get syntax highlighting in the output. >>> >>>> + >>>> +===== start of bash scripts ============= >>>> +#!/bin/bash >>>> + >>>> +while true ; do >>>> + while [ ! -d /sys/class/tty/ttyUSB0 ] ; do >>>> + : >>>> + done >>>> + cat /dev/ttyUSB0 >> xdbc.log >>>> +done >>>> +===== end of bash scripts =============== >>>> + >>>> +You should be able to see the early boot message in xdbc.log. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
