arm64: Add simple earlyprintk support
authorCatalin Marinas <catalin.marinas@arm.com>
Tue, 23 Oct 2012 13:55:08 +0000 (14:55 +0100)
committerCatalin Marinas <catalin.marinas@arm.com>
Tue, 22 Jan 2013 17:51:01 +0000 (17:51 +0000)
commit2475ff9d2c6ea3bbfed55c4635426c371f9ad327
treec705c9a55b2d9ea2d270b7002f568b6be0465ecd
parentd6bafb9b821a3a5ddeb600a9fd015085760d818e
arm64: Add simple earlyprintk support

This patch adds support for "earlyprintk=" parameter on the kernel
command line. The format is:

  earlyprintk=<name>[,<addr>][,<options>]

where <name> is the name of the (UART) device, e.g. "pl011", <addr> is
the I/O address. The <options> aren't currently used.

The mapping of the earlyprintk device is done very early during kernel
boot and there are restrictions on which functions it can call. A
special early_io_map() function is added which creates the mapping from
the pre-defined EARLY_IOBASE to the device I/O address passed via the
kernel parameter. The pgd entry corresponding to EARLY_IOBASE is
pre-populated in head.S during kernel boot.

Only PL011 is currently supported and it is assumed that the interface
is already initialised by the boot loader before the kernel is started.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Documentation/arm64/memory.txt
arch/arm64/Kconfig.debug
arch/arm64/include/asm/io.h
arch/arm64/include/asm/memory.h
arch/arm64/include/asm/mmu.h
arch/arm64/kernel/Makefile
arch/arm64/kernel/early_printk.c [new file with mode: 0644]
arch/arm64/kernel/head.S
arch/arm64/mm/mmu.c