powerpc/47x: allow kernel to be loaded in higher physical memory

The 44x code (which is shared by 47x) assumes the available physical memory
begins at 0x00000000.  This is not necessarily the case in an AMP
environment.

Support CONFIG_RELOCATABLE for 476 in order to allow the kernel to be
loaded into a higher memory range.

Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>
Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>

1 files changed, 34 insertions, 8 deletions

diff --git a/arch/powerpc/kernel/head_44x.S b/arch/powerpc/kernel/head_44x.S
index 5e12b741ba5f..f8e971ba94f5 100644
--- a/arch/powerpc/kernel/head_44x.S
+++ b/arch/powerpc/kernel/head_44x.S
@@ -93,6 +93,30 @@ _ENTRY(_start);
 
 	bl	early_init
 
+#ifdef CONFIG_RELOCATABLE
+	/*
+	 * r25 will contain RPN/ERPN for the start address of memory
+	 *
+	 * Add the difference between KERNELBASE and PAGE_OFFSET to the
+	 * start of physical memory to get kernstart_addr.
+	 */
+	lis	r3,kernstart_addr@ha
+	la	r3,kernstart_addr@l(r3)
+
+	lis	r4,KERNELBASE@h
+	ori	r4,r4,KERNELBASE@l
+	lis	r5,PAGE_OFFSET@h
+	ori	r5,r5,PAGE_OFFSET@l
+	subf	r4,r5,r4
+
+	rlwinm	r6,r25,0,28,31	/* ERPN */
+	rlwinm	r7,r25,0,0,3	/* RPN - assuming 256 MB page size */
+	add	r7,r7,r4
+
+	stw	r6,0(r3)
+	stw	r7,4(r3)
+#endif
+
 /*
  * Decide what sort of machine this is and initialize the MMU.
  */
@@ -1001,9 +1025,6 @@ clear_utlb_entry:
 	lis	r3,PAGE_OFFSET@h
 	ori	r3,r3,PAGE_OFFSET@l
 
-	/* Kernel is at the base of RAM */
-	li r4, 0			/* Load the kernel physical address */
-
 	/* Load the kernel PID = 0 */
 	li	r0,0
 	mtspr	SPRN_PID,r0
@@ -1013,9 +1034,8 @@ clear_utlb_entry:
 	clrrwi	r3,r3,12		/* Mask off the effective page number */
 	ori	r3,r3,PPC47x_TLB0_VALID | PPC47x_TLB0_256M
 
-	/* Word 1 */
-	clrrwi	r4,r4,12		/* Mask off the real page number */
-					/* ERPN is 0 for first 4GB page */
+	/* Word 1 - use r25.  RPN is the same as the original entry */
+
 	/* Word 2 */
 	li	r5,0
 	ori	r5,r5,PPC47x_TLB2_S_RWX
@@ -1026,7 +1046,7 @@ clear_utlb_entry:
 	/* We write to way 0 and bolted 0 */
 	lis	r0,0x8800
 	tlbwe	r3,r0,0
-	tlbwe	r4,r0,1
+	tlbwe	r25,r0,1
 	tlbwe	r5,r0,2
 
 /*
@@ -1124,7 +1144,13 @@ head_start_common:
 	lis	r4,interrupt_base@h	/* IVPR only uses the high 16-bits */
 	mtspr	SPRN_IVPR,r4
 
-	addis	r22,r22,KERNELBASE@h
+	/*
+	 * If the kernel was loaded at a non-zero 256 MB page, we need to
+	 * mask off the most significant 4 bits to get the relative address
+	 * from the start of physical memory
+	 */
+	rlwinm	r22,r22,0,4,31
+	addis	r22,r22,PAGE_OFFSET@h
 	mtlr	r22
 	isync
 	blr