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From: Bill Gatliff <bgat@billgatliff.com>
Date: Thu, 31 May 2007 21:02:22 +0000 (+0100)
Subject: [ARM] 4423/1: add ATAGS support
X-Git-Tag: v2.6.23-rc1~1101^2^7~5
X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=9d20fdd58e74d4d26dc5216efaaa0f800c23dd3a
[ARM] 4423/1: add ATAGS support
Examines the ATAGS pointer (r2) at boot, and interprets
a nonzero value as a reference to an ATAGS structure. A
suitable ATAGS structure replaces the kernel's command line.
Signed-off-by: Bill Gatliff <bgat@billgatliff.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index a52da0d..024a9cf 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -20,7 +20,8 @@ __switch_data:
.long _end @ r7
.long processor_id @ r4
.long __machine_arch_type @ r5
- .long cr_alignment @ r6
+ .long __atags_pointer @ r6
+ .long cr_alignment @ r7
.long init_thread_union + THREAD_START_SP @ sp
/*
@@ -29,6 +30,7 @@ __switch_data:
*
* r0 = cp#15 control register
* r1 = machine ID
+ * r2 = atags pointer
* r9 = processor ID
*/
.type __mmap_switched, %function
@@ -47,11 +49,12 @@ __mmap_switched:
strcc fp, [r6],#4
bcc 1b
- ldmia r3, {r4, r5, r6, sp}
+ ldmia r3, {r4, r5, r6, r7, sp}
str r9, [r4] @ Save processor ID
str r1, [r5] @ Save machine type
+ str r2, [r6] @ Save atags pointer
bic r4, r0, #CR_A @ Clear 'A' bit
- stmia r6, {r0, r4} @ Save control register values
+ stmia r7, {r0, r4} @ Save control register values
b start_kernel
/*
@@ -215,3 +218,34 @@ ENTRY(lookup_machine_type)
bl __lookup_machine_type
mov r0, r5
ldmfd sp!, {r4 - r6, pc}
+
+/* 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
+ * of this function may be more lenient with the physical address and
+ * may also be able to move the ATAGS block if necessary.
+ *
+ * r8 = machinfo
+ *
+ * Returns:
+ * r2 either valid atags pointer, or zero
+ * r5, r6 corrupted
+ */
+
+ .type __vet_atags, %function
+__vet_atags:
+ tst r2, #0x3 @ aligned?
+ bne 1f
+
+ ldr r5, [r2, #0] @ is first tag ATAG_CORE?
+ subs r5, r5, #ATAG_CORE_SIZE
+ bne 1f
+ ldr r5, [r2, #4]
+ ldr r6, =ATAG_CORE
+ cmp r5, r6
+ bne 1f
+
+ mov pc, lr @ atag pointer is ok
+
+1: mov r2, #0
+ mov pc, lr
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 41f98b4..7898cbc 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -29,6 +29,10 @@
#define KERNEL_RAM_VADDR (PAGE_OFFSET + TEXT_OFFSET)
#define KERNEL_RAM_PADDR (PHYS_OFFSET + TEXT_OFFSET)
+#define ATAG_CORE 0x54410001
+#define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
+
+
/*
* swapper_pg_dir is the virtual address of the initial page table.
* We place the page tables 16K below KERNEL_RAM_VADDR. Therefore, we must
@@ -61,7 +65,7 @@
*
* 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.
+ * r1 = machine nr, r2 = atags pointer.
*
* This code is mostly position independent, so if you link the kernel at
* 0xc0008000, you call this at __pa(0xc0008000).
@@ -85,6 +89,7 @@ ENTRY(stext)
bl __lookup_machine_type @ r5=machinfo
movs r8, r5 @ invalid machine (r5=0)?
beq __error_a @ yes, error 'a'
+ bl __vet_atags
bl __create_page_tables
/*
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 650eac1..5be2e98 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -63,6 +63,8 @@ unsigned int processor_id;
unsigned int __machine_arch_type;
EXPORT_SYMBOL(__machine_arch_type);
+unsigned int __atags_pointer __initdata;
+
unsigned int system_rev;
EXPORT_SYMBOL(system_rev);
@@ -780,7 +782,9 @@ void __init setup_arch(char **cmdline_p)
if (mdesc->soft_reboot)
reboot_setup("s");
- if (mdesc->boot_params)
+ if (__atags_pointer)
+ tags = phys_to_virt(__atags_pointer);
+ else if (mdesc->boot_params)
tags = phys_to_virt(mdesc->boot_params);
/*
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