[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 <galak@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

3 files changed, 16 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index 4ff74414356..e581524d85b 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -371,6 +371,17 @@ skpinv:	addi	r6,r6,1				/* Increment */
 
 	bl	early_init
 
+#ifdef CONFIG_RELOCATABLE
+	lis	r3,kernstart_addr@ha
+	la	r3,kernstart_addr@l(r3)
+#ifdef CONFIG_PHYS_64BIT
+	stw	r23,0(r3)
+	stw	r25,4(r3)
+#else
+	stw	r25,0(r3)
+#endif
+#endif
+
 	mfspr	r3,SPRN_TLB1CFG
 	andi.	r3,r3,0xfff
 	lis	r4,num_tlbcam_entries@ha
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 3bfe7837e82..2aefe2a4129 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -53,6 +53,7 @@
 #include <asm/pci-bridge.h>
 #include <asm/phyp_dump.h>
 #include <asm/kexec.h>
+#include <mm/mmu_decl.h>
 
 #ifdef DEBUG
 #define DBG(fmt...) printk(KERN_ERR fmt)
@@ -978,7 +979,10 @@ static int __init early_init_dt_scan_memory(unsigned long node,
 		}
 #endif
 		lmb_add(base, size);
+
+		memstart_addr = min((u64)memstart_addr, base);
 	}
+
 	return 0;
 }
 
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 31ada9fdfc5..153a48dc8f4 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -435,7 +435,7 @@ void __init setup_system(void)
 		printk("htab_address                  = 0x%p\n", htab_address);
 	printk("htab_hash_mask                = 0x%lx\n", htab_hash_mask);
 #if PHYSICAL_START > 0
-	printk("physical_start                = 0x%x\n", PHYSICAL_START);
+	printk("physical_start                = 0x%lx\n", PHYSICAL_START);
 #endif
 	printk("-----------------------------------------------------\n");