[PATCH] Fix data abort in startup for at91 machines based on ARM926EJS

[Martin Townsend]

The startup code in arm/cpu/arm926ejs preserves the link register across
the call to lowlevel_init by using r4:

mov	r4, lr		/* perserve link reg across call */
bl	lowlevel_init	/* go setup pll,mux,memory */
mov	lr, r4		/* restore link */

The lowlevel_init function for at91 machines based on the same CPU uses r4
and hence corrupts it causing a data abort when it returns to the startup
code. This patch fixes this by using r6 instead of r4 in the lowlevel_init
function.

Discovered and the fix was tested on a AT91SAM9261 based board.

Signed-off-by: Martin Townsend <martin at rufilla.com>
---
 arch/arm/mach-at91/arm926ejs/lowlevel_init.S | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/arm/mach-at91/arm926ejs/lowlevel_init.S b/arch/arm/mach-at91/arm926ejs/lowlevel_init.S
index 71d7582ce0..994f42eb4a 100644
--- a/arch/arm/mach-at91/arm926ejs/lowlevel_init.S
+++ b/arch/arm/mach-at91/arm926ejs/lowlevel_init.S
@@ -71,10 +71,10 @@ POS1:
 	str	r0, [r1]
 
 	/* Reading the PMC Status to detect when the Main Oscillator is enabled */
-	mov	r4, #AT91_PMC_IXR_MOSCS
+	mov	r6, #AT91_PMC_IXR_MOSCS
 MOSCS_Loop:
 	ldr	r3, [r2]
-	and	r3, r4, r3
+	and	r3, r6, r3
 	cmp	r3, #AT91_PMC_IXR_MOSCS
 	bne	MOSCS_Loop
 
@@ -89,10 +89,10 @@ MOSCS_Loop:
 	str	r0, [r1]
 
 	/* Reading the PMC Status register to detect when the PLLA is locked */
-	mov	r4, #AT91_PMC_IXR_LOCKA
+	mov	r6, #AT91_PMC_IXR_LOCKA
 MOSCS_Loop1:
 	ldr	r3, [r2]
-	and	r3, r4, r3
+	and	r3, r6, r3
 	cmp	r3, #AT91_PMC_IXR_LOCKA
 	bne	MOSCS_Loop1
 
@@ -109,10 +109,10 @@ MOSCS_Loop1:
 	str	r0, [r1]
 
 	/* Reading the PMC Status to detect when the Master clock is ready */
-	mov	r4, #AT91_PMC_IXR_MCKRDY
+	mov	r6, #AT91_PMC_IXR_MCKRDY
 MCKRDY_Loop:
 	ldr	r3, [r2]
-	and	r3, r4, r3
+	and	r3, r6, r3
 	cmp	r3, #AT91_PMC_IXR_MCKRDY
 	bne	MCKRDY_Loop
 
@@ -120,10 +120,10 @@ MCKRDY_Loop:
 	str	r0, [r1]
 
 	/* Reading the PMC Status to detect when the Master clock is ready */
-	mov	r4, #AT91_PMC_IXR_MCKRDY
+	mov	r6, #AT91_PMC_IXR_MCKRDY
 MCKRDY_Loop1:
 	ldr	r3, [r2]
-	and	r3, r4, r3
+	and	r3, r6, r3
 	cmp	r3, #AT91_PMC_IXR_MCKRDY
 	bne	MCKRDY_Loop1
 PLL_setup_end:
-- 
2.25.1