[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>

[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>
Bill Gatliff · Russell King
1 parent 7d09e85448
Showing 3 changed files with 48 additions and 5 deletions Side-by-side Diff
arch/arm/kernel/head-common.S
arch/arm/kernel/head.S
arch/arm/kernel/setup.c
@@ -20,7 +20,8 @@
 	.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 @@
  *
  *  r0  = cp#15 control register
  *  r1  = machine ID
+ *  r2  = atags pointer
  *  r9  = processor ID
  */
 	.type	__mmap_switched, %function
  
  
@@ -47,11 +49,12 @@
 	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
  
 /*
@@ -215,4 +218,35 @@
 	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
@@ -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 @@
 	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
  
 	/*
@@ -63,6 +63,8 @@
 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 @@
 	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);
  
 	/*
...	...	@@ -20,7 +20,8 @@
20	20	.long _end @ r7
21	21	.long processor_id @ r4
22	22	.long __machine_arch_type @ r5
23		- .long cr_alignment @ r6
	23	+ .long __atags_pointer @ r6
	24	+ .long cr_alignment @ r7
24	25	.long init_thread_union + THREAD_START_SP @ sp
25	26
26	27	/*
...	...	@@ -29,6 +30,7 @@
29	30	*
30	31	* r0 = cp#15 control register
31	32	* r1 = machine ID
	33	+ * r2 = atags pointer
32	34	* r9 = processor ID
33	35	*/
34	36	.type __mmap_switched, %function
35	37
36	38
...	...	@@ -47,11 +49,12 @@
47	49	strcc fp, [r6],#4
48	50	bcc 1b
49	51
50		- ldmia r3, {r4, r5, r6, sp}
	52	+ ldmia r3, {r4, r5, r6, r7, sp}
51	53	str r9, [r4] @ Save processor ID
52	54	str r1, [r5] @ Save machine type
	55	+ str r2, [r6] @ Save atags pointer
53	56	bic r4, r0, #CR_A @ Clear 'A' bit
54		- stmia r6, {r0, r4} @ Save control register values
	57	+ stmia r7, {r0, r4} @ Save control register values
55	58	b start_kernel
56	59
57	60	/*
...	...	@@ -215,4 +218,35 @@
215	218	bl __lookup_machine_type
216	219	mov r0, r5
217	220	ldmfd sp!, {r4 - r6, pc}
	221	+
	222	+/* Determine validity of the r2 atags pointer. The heuristic requires
	223	+ * that the pointer be aligned, in the first 16k of physical RAM and
	224	+ * that the ATAG_CORE marker is first and present. Future revisions
	225	+ * of this function may be more lenient with the physical address and
	226	+ * may also be able to move the ATAGS block if necessary.
	227	+ *
	228	+ * r8 = machinfo
	229	+ *
	230	+ * Returns:
	231	+ * r2 either valid atags pointer, or zero
	232	+ * r5, r6 corrupted
	233	+ */
	234	+
	235	+ .type __vet_atags, %function
	236	+__vet_atags:
	237	+ tst r2, #0x3 @ aligned?
	238	+ bne 1f
	239	+
	240	+ ldr r5, [r2, #0] @ is first tag ATAG_CORE?
	241	+ subs r5, r5, #ATAG_CORE_SIZE
	242	+ bne 1f
	243	+ ldr r5, [r2, #4]
	244	+ ldr r6, =ATAG_CORE
	245	+ cmp r5, r6
	246	+ bne 1f
	247	+
	248	+ mov pc, lr @ atag pointer is ok
	249	+
	250	+1: mov r2, #0
	251	+ mov pc, lr
...	...	@@ -29,6 +29,10 @@
29	29	#define KERNEL_RAM_VADDR (PAGE_OFFSET + TEXT_OFFSET)
30	30	#define KERNEL_RAM_PADDR (PHYS_OFFSET + TEXT_OFFSET)
31	31
	32	+#define ATAG_CORE 0x54410001
	33	+#define ATAG_CORE_SIZE ((24 + 34) >> 2)
	34	+
	35	+
32	36	/*
33	37	* swapper_pg_dir is the virtual address of the initial page table.
34	38	* We place the page tables 16K below KERNEL_RAM_VADDR. Therefore, we must
...	...	@@ -61,7 +65,7 @@
61	65	*
62	66	* This is normally called from the decompressor code. The requirements
63	67	* are: MMU = off, D-cache = off, I-cache = dont care, r0 = 0,
64		- * r1 = machine nr.
	68	+ * r1 = machine nr, r2 = atags pointer.
65	69	*
66	70	* This code is mostly position independent, so if you link the kernel at
67	71	* 0xc0008000, you call this at __pa(0xc0008000).
...	...	@@ -85,6 +89,7 @@
85	89	bl __lookup_machine_type @ r5=machinfo
86	90	movs r8, r5 @ invalid machine (r5=0)?
87	91	beq __error_a @ yes, error 'a'
	92	+ bl __vet_atags
88	93	bl __create_page_tables
89	94
90	95	/*
...	...	@@ -63,6 +63,8 @@
63	63	unsigned int __machine_arch_type;
64	64	EXPORT_SYMBOL(__machine_arch_type);
65	65
	66	+unsigned int __atags_pointer __initdata;
	67	+
66	68	unsigned int system_rev;
67	69	EXPORT_SYMBOL(system_rev);
68	70
...	...	@@ -780,7 +782,9 @@
780	782	if (mdesc->soft_reboot)
781	783	reboot_setup("s");
782	784
783		- if (mdesc->boot_params)
	785	+ if (__atags_pointer)
	786	+ tags = phys_to_virt(__atags_pointer);
	787	+ else if (mdesc->boot_params)
784	788	tags = phys_to_virt(mdesc->boot_params);
785	789
786	790	/*