From 37dd2badcfcec35f5e21a0926968d77a404f03c3 Mon Sep 17 00:00:00 2001 From: Kumar Gala Date: Tue, 22 Apr 2008 04:22:34 +1000 Subject: [POWERPC] 85xx: Add support for relocatable kernel (and booting at non-zero) Added support to allow an 85xx kernel to be run from a non-zero physical address (useful for cooperative asymmetric multiprocessing situations and kdump). The support can be configured at compile time by setting CONFIG_PAGE_OFFSET, CONFIG_KERNEL_START, and CONFIG_PHYSICAL_START as desired. Alternatively, the kernel build can set CONFIG_RELOCATABLE. Setting this config option causes the kernel to determine at runtime the physical addresses of CONFIG_PAGE_OFFSET and CONFIG_KERNEL_START. If CONFIG_RELOCATABLE is set, then CONFIG_PHYSICAL_START has no meaning. However, CONFIG_PHYSICAL_START will always be used to set the LOAD program header physical address field in the resulting ELF image. Currently we are limited to running at a physical address that is a multiple of 256M. This is due to how we map TLBs to cover lowmem. This should be fixed to allow 64M or maybe even 16M alignment in the future. It is considered an error to try and run a kernel at a non-aligned physical address. All the magic for this support is accomplished by proper initialization of the kernel memory subsystem and use of ARCH_PFN_OFFSET. The use of ARCH_PFN_OFFSET only affects normal memory and not IO mappings. ioremap uses map_page and isn't affected by ARCH_PFN_OFFSET. /dev/mem continues to allow access to any physical address in the system regardless of how CONFIG_PHYSICAL_START is set. Signed-off-by: Kumar Gala Signed-off-by: Paul Mackerras --- arch/powerpc/mm/init_64.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/powerpc/mm/init_64.c') diff --git a/arch/powerpc/mm/init_64.c b/arch/powerpc/mm/init_64.c index 698bd000f98b..c5ac532a0161 100644 --- a/arch/powerpc/mm/init_64.c +++ b/arch/powerpc/mm/init_64.c @@ -72,7 +72,8 @@ #warning TASK_SIZE is smaller than it needs to be. #endif -phys_addr_t memstart_addr; +phys_addr_t memstart_addr = ~0; +phys_addr_t kernstart_addr; void free_initmem(void) { -- cgit v1.2.3