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'. 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. > -- Jani Nikula, Intel Open Source Technology Center -- 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
