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Commit 9780bc41 authored by Jason Wessel's avatar Jason Wessel Committed by Greg Kroah-Hartman
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USB: ehci-dbgp,documentation: Documentation updates for ehci-dbgp 



Add missing information about requirements of using the EHCI usb debug
controller as well as to mention you can use a debug controller other
than the first one in the system.

Signed-off-by: default avatarJason Wessel <jason.wessel@windriver.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Sarah Sharp <sarah.a.sharp@intel.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 68d2956a

Documentation/kernel-parameters.txt

+1 −1
Original line number Original line Diff line number Diff line
@@ -671,7 +671,7 @@ and is between 256 and 4096 characters. It is defined in the file 
	earlyprintk=	[X86,SH,BLACKFIN]

	earlyprintk=	[X86,SH,BLACKFIN]

			earlyprintk=vga

			earlyprintk=vga

			earlyprintk=serial[,ttySn[,baudrate]]

			earlyprintk=serial[,ttySn[,baudrate]]

			earlyprintk=dbgp

			earlyprintk=dbgp[debugController#]





			Append ",keep" to not disable it when the real console

			Append ",keep" to not disable it when the real console

			takes over.

			takes over.

Documentation/x86/earlyprintk.txt

+37 −2
Original line number Original line Diff line number Diff line
@@ -7,7 +7,7 @@ and two USB cables, connected like this: 




  [host/target] <-------> [USB debug key] <-------> [client/console]

  [host/target] <-------> [USB debug key] <-------> [client/console]





1. There are three specific hardware requirements:

1. There are a number of specific hardware requirements:





 a.) Host/target system needs to have USB debug port capability.

 a.) Host/target system needs to have USB debug port capability.
@@ -42,7 +42,35 @@ and two USB cables, connected like this: 
     This is a small blue plastic connector with two USB connections,

     This is a small blue plastic connector with two USB connections,

     it draws power from its USB connections.

     it draws power from its USB connections.





 c.) Thirdly, you need a second client/console system with a regular USB port.

 c.) You need a second client/console system with a high speed USB 2.0

     port.



 d.) The Netchip device must be plugged directly into the physical

     debug port on the "host/target" system.  You cannot use a USB hub in

     between the physical debug port and the "host/target" system.



     The EHCI debug controller is bound to a specific physical USB

     port and the Netchip device will only work as an early printk

     device in this port.  The EHCI host controllers are electrically

     wired such that the EHCI debug controller is hooked up to the

     first physical and there is no way to change this via software.

     You can find the physical port through experimentation by trying

     each physical port on the system and rebooting.  Or you can try

     and use lsusb or look at the kernel info messages emitted by the

     usb stack when you plug a usb device into various ports on the

     "host/target" system.



     Some hardware vendors do not expose the usb debug port with a

     physical connector and if you find such a device send a complaint

     to the hardware vendor, because there is no reason not to wire

     this port into one of the physically accessible ports.



 e.) It is also important to note, that many versions of the Netchip

     device require the "client/console" system to be plugged into the

     right and side of the device (with the product logo facing up and

     readable left to right).  The reason being is that the 5 volt

     power supply is taken from only one side of the device and it

     must be the side that does not get rebooted.





2. Software requirements:

2. Software requirements:
@@ -56,6 +84,13 @@ and two USB cables, connected like this: 
    (If you are using Grub, append it to the 'kernel' line in

    (If you are using Grub, append it to the 'kernel' line in

     /etc/grub.conf)

     /etc/grub.conf)





    On systems with more than one EHCI debug controller you must

    specify the correct EHCI debug controller number.  The ordering

    comes from the PCI bus enumeration of the EHCI controllers.  The

    default with no number argument is "0" the first EHCI debug

    controller.  To use the second EHCI debug controller, you would

    use the command line: "earlyprintk=dbgp1"



    NOTE: normally earlyprintk console gets turned off once the

    NOTE: normally earlyprintk console gets turned off once the

    regular console is alive - use "earlyprintk=dbgp,keep" to keep

    regular console is alive - use "earlyprintk=dbgp,keep" to keep

    this channel open beyond early bootup. This can be useful for

    this channel open beyond early bootup. This can be useful for