[PATCH v3 1/6] arm/dt: Make __vet_atags also accept a dtb image

Grant Likely
2011-02-12T08:14:32Z

The dtb is passed to the kernel via register r2, which is the same
method that is used to pass an atags pointer. This patch modifies
__vet_atags to not clear r2 when it encounters a dtb image.

v2: fixed bugs pointed out by Nicolas Pitre

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
---
arch/arm/kernel/head-common.S | 24 ++++++++++++++++++------
arch/arm/kernel/head.S | 8 ++++----
2 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index c84b57d..854bd22 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -15,6 +15,12 @@
#define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
#define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)

+#ifdef CONFIG_CPU_BIG_ENDIAN
+#define OF_DT_MAGIC 0xd00dfeed
+#else
+#define OF_DT_MAGIC 0xedfe0dd0 /* 0xd00dfeed in big-endian */
+#endif
+
/*
* Exception handling. Something went wrong and we can't proceed. We
* ought to tell the user, but since we don't have any guarantee that
@@ -28,20 +34,26 @@

/* Determine validity of the r2 atags pointer. The heuristic requires
* that the pointer be aligned, in the first 16k of physical RAM and
- * that the ATAG_CORE marker is first and present. Future revisions
+ * that the ATAG_CORE marker is first and present. If CONFIG_OF_FLATTREE
+ * is selected, then it will also accept a dtb pointer. Future revisions
* of this function may be more lenient with the physical address and
* may also be able to move the ATAGS block if necessary.
*
* Returns:
- * r2 either valid atags pointer, or zero
+ * r2 either valid atags pointer, valid dtb pointer, or zero
* r5, r6 corrupted
*/
__vet_atags:
tst r2, #0x3 @ aligned?
bne 1f

- ldr r5, [r2, #0] @ is first tag ATAG_CORE?
- cmp r5, #ATAG_CORE_SIZE
+ ldr r5, [r2, #0]
+#ifdef CONFIG_OF_FLATTREE
+ ldr r6, =OF_DT_MAGIC @ is it a DTB?
+ cmp r5, r6
+ beq 2f
+#endif
+ cmp r5, #ATAG_CORE_SIZE @ is first tag ATAG_CORE?
cmpne r5, #ATAG_CORE_SIZE_EMPTY
bne 1f
ldr r5, [r2, #4]
@@ -49,7 +61,7 @@ __vet_atags:
cmp r5, r6
bne 1f

- mov pc, lr @ atag pointer is ok
+2: mov pc, lr @ atag/dtb pointer is ok

1: mov r2, #0
mov pc, lr
@@ -61,7 +73,7 @@ ENDPROC(__vet_atags)
*
* r0 = cp#15 control register
* r1 = machine ID
- * r2 = atags pointer
+ * r2 = atags/dtb pointer
* r9 = processor ID
*/
__INIT
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 941f6ea..180427d 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -66,7 +66,7 @@
*
* This is normally called from the decompressor code. The requirements
* are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
- * r1 = machine nr, r2 = atags pointer.
+ * r1 = machine nr, r2 = atags or dtb pointer.
*
* This code is mostly position independent, so if you link the kernel at
* 0xc0008000, you call this at __pa(0xc0008000).
@@ -89,7 +89,7 @@ ENTRY(stext)
beq __error_p @ yes, error 'p'

/*
- * r1 = machine no, r2 = atags,
+ * r1 = machine no, r2 = atags or dtb,
* r9 = cpuid, r10 = procinfo
*/
bl __vet_atags
@@ -347,7 +347,7 @@ __secondary_data:
*
* r0 = cp#15 control register
* r1 = machine ID
- * r2 = atags pointer
+ * r2 = atags or dtb pointer
* r4 = page table pointer
* r9 = processor ID
* r13 = *virtual* address to jump to upon completion
@@ -384,7 +384,7 @@ ENDPROC(__enable_mmu)
*
* r0 = cp#15 control register
* r1 = machine ID
- * r2 = atags pointer
+ * r2 = atags or dtb pointer
* r9 = processor ID
* r13 = *virtual* address to jump to upon completion
*