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[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>
This commit is contained in:
Bill Gatliff 2007-05-31 22:02:22 +01:00 committed by Russell King
parent 7d09e85448
commit 9d20fdd58e
3 changed files with 48 additions and 5 deletions
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40
arch/arm/kernel/head-common.S
View File

@ -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

7
arch/arm/kernel/head.S
View File

@ -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
/*

6
arch/arm/kernel/setup.c
View File

@ -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);
/*