path: root/arch/arm64/Kconfig.debug
diff options
authorCatalin Marinas <>2012-10-23 14:55:08 +0100
committerCatalin Marinas <>2013-01-22 17:51:01 +0000
commit2475ff9d2c6ea3bbfed55c4635426c371f9ad327 (patch)
treec705c9a55b2d9ea2d270b7002f568b6be0465ecd /arch/arm64/Kconfig.debug
parentd6bafb9b821a3a5ddeb600a9fd015085760d818e (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 <> Acked-by: Arnd Bergmann <>
Diffstat (limited to 'arch/arm64/Kconfig.debug')
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index d7553f2bda66..79871cd78da8 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -24,4 +24,13 @@ config DEBUG_STACK_USAGE
Enables the display of the minimum amount of free stack which each
task has ever had available in the sysrq-T output.
+ bool "Early printk support"
+ default y
+ help
+ Say Y here if you want to have an early console using the
+ earlyprintk=<name>[,<addr>][,<options>] kernel parameter. It
+ is assumed that the early console device has been initialised
+ by the boot loader prior to starting the Linux kernel.