diff options
| author | Catalin Marinas <catalin.marinas@arm.com> | 2012-10-23 14:55:08 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2013-01-22 17:51:01 +0000 |
| commit | 2475ff9d2c6ea3bbfed55c4635426c371f9ad327 (patch) | |
| tree | c705c9a55b2d9ea2d270b7002f568b6be0465ecd /arch/arm64/include/asm/memory.h | |
| parent | d6bafb9b821a3a5ddeb600a9fd015085760d818e (diff) | |
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>
Diffstat (limited to 'arch/arm64/include/asm/memory.h')
| -rw-r--r-- | arch/arm64/include/asm/memory.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index 1cac16a001c..381f556b664 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -43,6 +43,7 @@ #define PAGE_OFFSET UL(0xffffffc000000000) #define MODULES_END (PAGE_OFFSET) #define MODULES_VADDR (MODULES_END - SZ_64M) +#define EARLYCON_IOBASE (MODULES_VADDR - SZ_4M) #define VA_BITS (39) #define TASK_SIZE_64 (UL(1) << VA_BITS) |