arm: Allow lr to be saved by board code

The link register value can be required on some boards (e.g. FEL mode on sunxi) so use a branch instruction to jump to save_boot_params() instead of a branch link. This requires a branch back to save_boot_params_ret so adjust the users to deal with this. For exynos just drop the function since it doesn't do anything. Signed-off-by: Simon Glass <sjg@chromium.org> Acked-by: Siarhei Siamashka <siarhei.siamashka@gmail.com> Acked-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

arm: Allow lr to be saved by board code
The link register value can be required on some boards (e.g. FEL mode on sunxi) so use a branch instruction to jump to save_boot_params() instead of a branch link. This requires a branch back to save_boot_params_ret so adjust the users to deal with this. For exynos just drop the function since it doesn't do anything. Signed-off-by: Simon Glass <sjg@chromium.org> Acked-by: Siarhei Siamashka <siarhei.siamashka@gmail.com> Acked-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Simon Glass · Hans de Goede · Eric Lee · Eric Lee · Eric Lee · Eric Lee
1 parent c924e2a803
Showing 6 changed files with 24 additions and 6 deletions Side-by-side Diff
arch/arm/cpu/armv7/exynos/spl_boot.c
arch/arm/cpu/armv7/omap-common/lowlevel_init.S
arch/arm/cpu/armv7/omap3/lowlevel_init.S
arch/arm/cpu/armv7/start.S
arch/arm/include/asm/system.h
board/nokia/rx51/lowlevel_init.S
@@ -309,5 +309,4 @@
 	while (1)
 		;
 }
-void save_boot_params(u32 r0, u32 r1, u32 r2, u32 r3) {}
@@ -19,7 +19,7 @@
 ENTRY(save_boot_params)
 	ldr	r1, =OMAP_SRAM_SCRATCH_BOOT_PARAMS
 	str	r0, [r1]
-	bx	lr
+	b	save_boot_params_ret
 ENDPROC(save_boot_params)
  
 ENTRY(set_pl310_ctrl_reg)
@@ -23,7 +23,7 @@
 	ldr	r5, [r0, #0x4]
 	and	r5, r5, #0xff
 	str	r5, [r4]
-	bx	lr
+	b	save_boot_params_ret
 ENDPROC(save_boot_params)
 #endif
  
@@ -31,9 +31,12 @@
  *************************************************************************/
  
 	.globl	reset
+	.globl	save_boot_params_ret
  
 reset:
-	bl	save_boot_params
+	/* Allow the board to save important registers */
+	b	save_boot_params
+save_boot_params_ret:
 	/*
 	 * disable interrupts (FIQ and IRQ), also set the cpu to SVC32 mode,
 	 * except if in HYP mode already
@@ -96,7 +99,7 @@
  *
  *************************************************************************/
 ENTRY(save_boot_params)
-	bx	lr			@ back to my caller
+	b	save_boot_params_ret		@ back to my caller
 ENDPROC(save_boot_params)
 	.weak	save_boot_params
  
@@ -142,6 +142,21 @@
  
 #ifndef __ASSEMBLY__
  
+/**
+ * save_boot_params() - Save boot parameters before starting reset sequence
+ *
+ * If you provide this function it will be called immediately U-Boot starts,
+ * both for SPL and U-Boot proper.
+ *
+ * All registers are unchanged from U-Boot entry. No registers need be
+ * preserved.
+ *
+ * This is not a normal C function. There is no stack. Return by branching to
+ * save_boot_params_ret.
+ *
+ * void save_boot_params(u32 r0, u32 r1, u32 r2, u32 r3);
+ */
+
 #define isb() __asm__ __volatile__ ("" : : : "memory")
  
 #define nop() __asm__ __volatile__("mov\tr0,r0\t@ nop\n\t");
@@ -37,7 +37,8 @@
  
 .global save_boot_params
 save_boot_params:
-
+	/* Get return address */
+	ldr	lr, =save_boot_params_ret
  
 /* Copy valid attached kernel to address KERNEL_ADDRESS */
...	...	@@ -309,5 +309,4 @@
309	309	while (1)
310	310	;
311	311	}
312		-void save_boot_params(u32 r0, u32 r1, u32 r2, u32 r3) {}
...	...	@@ -19,7 +19,7 @@
19	19	ENTRY(save_boot_params)
20	20	ldr r1, =OMAP_SRAM_SCRATCH_BOOT_PARAMS
21	21	str r0, [r1]
22		- bx lr
	22	+ b save_boot_params_ret
23	23	ENDPROC(save_boot_params)
24	24
25	25	ENTRY(set_pl310_ctrl_reg)
...	...	@@ -23,7 +23,7 @@
23	23	ldr r5, [r0, #0x4]
24	24	and r5, r5, #0xff
25	25	str r5, [r4]
26		- bx lr
	26	+ b save_boot_params_ret
27	27	ENDPROC(save_boot_params)
28	28	#endif
29	29
...	...	@@ -31,9 +31,12 @@
31	31	*************************************************************************/
32	32
33	33	.globl reset
	34	+ .globl save_boot_params_ret
34	35
35	36	reset:
36		- bl save_boot_params
	37	+ /* Allow the board to save important registers */
	38	+ b save_boot_params
	39	+save_boot_params_ret:
37	40	/*
38	41	* disable interrupts (FIQ and IRQ), also set the cpu to SVC32 mode,
39	42	* except if in HYP mode already
...	...	@@ -96,7 +99,7 @@
96	99	*
97	100	*************************************************************************/
98	101	ENTRY(save_boot_params)
99		- bx lr @ back to my caller
	102	+ b save_boot_params_ret @ back to my caller
100	103	ENDPROC(save_boot_params)
101	104	.weak save_boot_params
102	105
...	...	@@ -142,6 +142,21 @@
142	142
143	143	#ifndef __ASSEMBLY__
144	144
	145	+/**
	146	+ * save_boot_params() - Save boot parameters before starting reset sequence
	147	+ *
	148	+ * If you provide this function it will be called immediately U-Boot starts,
	149	+ * both for SPL and U-Boot proper.
	150	+ *
	151	+ * All registers are unchanged from U-Boot entry. No registers need be
	152	+ * preserved.
	153	+ *
	154	+ * This is not a normal C function. There is no stack. Return by branching to
	155	+ * save_boot_params_ret.
	156	+ *
	157	+ * void save_boot_params(u32 r0, u32 r1, u32 r2, u32 r3);
	158	+ */
	159	+
145	160	#define isb() __asm__ __volatile__ ("" : : : "memory")
146	161
147	162	#define nop() __asm__ __volatile__("mov\tr0,r0\t@ nop\n\t");
...	...	@@ -37,7 +37,8 @@
37	37
38	38	.global save_boot_params
39	39	save_boot_params:
40		-
	40	+ /* Get return address */
	41	+ ldr lr, =save_boot_params_ret
41	42
42	43	/* Copy valid attached kernel to address KERNEL_ADDRESS */
43	44