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x86, early-printk: Update earlyprintk documentation (and kill x86 copy)

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Documentation/kernel-parameters.txt and
Documentation/x86/x86_64/boot-options.txt contain virtually
identical text describing earlyprintk.

This consolidates the two copies and updates the documentation a
bit.  No one ever documented the:

	earlyprintk=serial,0x1008,115200

syntax, nor mentioned that ARM is now a supported earlyprintk
arch.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Rob Landley <rob@landley.net>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave@sr71.net>
Link: http://lkml.kernel.org/r/20130410210338.E2930E98@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Dave Hansen
2013-04-10 14:03:38 -07:00
committed by Ingo Molnar
parent c391c78846
commit 147ea09119
2 changed files with 14 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
Documentation/kernel-parameters.txt
View File

@@ -757,19 +757,31 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
(mmio) or 32-bit (mmio32). (mmio) or 32-bit (mmio32).
The options are the same as for ttyS, above. The options are the same as for ttyS, above.
earlyprintk= [X86,SH,BLACKFIN] earlyprintk= [X86,SH,BLACKFIN,ARM]
earlyprintk=vga earlyprintk=vga
earlyprintk=xen earlyprintk=xen
earlyprintk=serial[,ttySn[,baudrate]] earlyprintk=serial[,ttySn[,baudrate]]
earlyprintk=serial[,0x...[,baudrate]]
earlyprintk=ttySn[,baudrate] earlyprintk=ttySn[,baudrate]
earlyprintk=dbgp[debugController#] 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 Append ",keep" to not disable it when the real console
takes over. takes over.
Only vga or serial or usb debug port at a time. 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 Interaction with the standard serial driver is not
very good. very good.

14
Documentation/x86/x86_64/boot-options.txt
View File

@@ -91,20 +91,6 @@ APICs
apicmaintimer. Useful when your PIT timer is totally apicmaintimer. Useful when your PIT timer is totally
broken. broken.
Early Console
syntax: earlyprintk=vga
earlyprintk=serial[,ttySn[,baudrate]]
The early console 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 at a time, not both.
Currently only ttyS0 and ttyS1 are supported.
Interaction with the standard serial driver is not very good.
The VGA output is eventually overwritten by the real console.
Timing Timing
notsc notsc