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-rw-r--r--Documentation/kernel-parameters.txt16
1 files changed, 14 insertions, 2 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4609e81dbc37..b5cfd047becb 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -757,19 +757,31 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
(mmio) or 32-bit (mmio32).
The options are the same as for ttyS, above.
- earlyprintk= [X86,SH,BLACKFIN]
+ earlyprintk= [X86,SH,BLACKFIN,ARM]
earlyprintk=vga
earlyprintk=xen
earlyprintk=serial[,ttySn[,baudrate]]
+ earlyprintk=serial[,0x...[,baudrate]]
earlyprintk=ttySn[,baudrate]
earlyprintk=dbgp[debugController#]
+ earlyprintk is useful when the kernel crashes before
+ the normal console is initialized. It is not enabled by
+ default because it has some cosmetic problems.
+
Append ",keep" to not disable it when the real console
takes over.
Only vga or serial or usb debug port at a time.
- Currently only ttyS0 and ttyS1 are supported.
+ Currently only ttyS0 and ttyS1 may be specified by
+ name. Other I/O ports may be explicitly specified
+ on some architectures (x86 and arm at least) by
+ replacing ttySn with an I/O port address, like this:
+ earlyprintk=serial,0x1008,115200
+ You can find the port for a given device in
+ /proc/tty/driver/serial:
+ 2: uart:ST16650V2 port:00001008 irq:18 ...
Interaction with the standard serial driver is not
very good.

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