--- /dev/null
+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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