Eric Lee / smarc-ti-linux-kernel

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Commit 9780bc41dca728f9b082a42d9e1f1716d5057081

Authored by Jason Wessel
Committed by Greg Kroah-Hartman
1 parent 68d2956a81
Exists in master and in 20 other branches dlt-processor-sdk-linux-03.00.00.04, newt-ti-linux-3.12.y, processor-sdk-linux-01.00.00, processor-sdk-linux-02.00.01, smarc-ti-linux-3.12.10, smarc-ti-linux-3.12.y, smarc-ti-linux-3.14.y, smarc-ti-linux-3.15.y, smarc-ti-lsk-linux-4.1.y, smarct3x-processor-sdk-04.01.00.06, smarct3x-processor-sdk-linux-02.00.01, smarct3x-processor-sdk-linux-03.00.00.04, smarct4x-800-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-04.01.00.06, smarct4x-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-linux-03.00.00.04, ti-linux-3.12.y, ti-linux-3.14.y, ti-linux-3.15.y, ti-lsk-linux-4.1.y

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: Jason 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: Greg Kroah-Hartman <gregkh@suse.de>

Showing 2 changed files with 38 additions and 3 deletions Side-by-side Diff

Documentation/kernel-parameters.txt
Diff comments   View file @ 9780bc4
... ... @@ -671,7 +671,7 @@
671 671 earlyprintk= [X86,SH,BLACKFIN]
672 672 earlyprintk=vga
673 673 earlyprintk=serial[,ttySn[,baudrate]]
674   - earlyprintk=dbgp
  674 + earlyprintk=dbgp[debugController#]
675 675  
676 676 Append ",keep" to not disable it when the real console
677 677 takes over.
Documentation/x86/earlyprintk.txt
Diff comments   View file @ 9780bc4
... ... @@ -7,7 +7,7 @@
7 7  
8 8 [host/target] <-------> [USB debug key] <-------> [client/console]
9 9  
10   -1. There are three specific hardware requirements:
  10 +1. There are a number of specific hardware requirements:
11 11  
12 12 a.) Host/target system needs to have USB debug port capability.
13 13  
14 14  
... ... @@ -42,8 +42,36 @@
42 42 This is a small blue plastic connector with two USB connections,
43 43 it draws power from its USB connections.
44 44  
45   - c.) Thirdly, you need a second client/console system with a regular USB port.
  45 + c.) You need a second client/console system with a high speed USB 2.0
  46 + port.
46 47  
  48 + d.) The Netchip device must be plugged directly into the physical
  49 + debug port on the "host/target" system. You cannot use a USB hub in
  50 + between the physical debug port and the "host/target" system.
  51 +
  52 + The EHCI debug controller is bound to a specific physical USB
  53 + port and the Netchip device will only work as an early printk
  54 + device in this port. The EHCI host controllers are electrically
  55 + wired such that the EHCI debug controller is hooked up to the
  56 + first physical and there is no way to change this via software.
  57 + You can find the physical port through experimentation by trying
  58 + each physical port on the system and rebooting. Or you can try
  59 + and use lsusb or look at the kernel info messages emitted by the
  60 + usb stack when you plug a usb device into various ports on the
  61 + "host/target" system.
  62 +
  63 + Some hardware vendors do not expose the usb debug port with a
  64 + physical connector and if you find such a device send a complaint
  65 + to the hardware vendor, because there is no reason not to wire
  66 + this port into one of the physically accessible ports.
  67 +
  68 + e.) It is also important to note, that many versions of the Netchip
  69 + device require the "client/console" system to be plugged into the
  70 + right and side of the device (with the product logo facing up and
  71 + readable left to right). The reason being is that the 5 volt
  72 + power supply is taken from only one side of the device and it
  73 + must be the side that does not get rebooted.
  74 +
47 75 2. Software requirements:
48 76  
49 77 a.) On the host/target system:
... ... @@ -55,6 +83,13 @@
55 83 And you need to add the boot command line: "earlyprintk=dbgp".
56 84 (If you are using Grub, append it to the 'kernel' line in
57 85 /etc/grub.conf)
  86 +
  87 + On systems with more than one EHCI debug controller you must
  88 + specify the correct EHCI debug controller number. The ordering
  89 + comes from the PCI bus enumeration of the EHCI controllers. The
  90 + default with no number argument is "0" the first EHCI debug
  91 + controller. To use the second EHCI debug controller, you would
  92 + use the command line: "earlyprintk=dbgp1"
58 93  
59 94 NOTE: normally earlyprintk console gets turned off once the
60 95 regular console is alive - use "earlyprintk=dbgp,keep" to keep