ARM: mach-at91: arm926ejs: fix data abort in startup returning from lowlevel_init

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@rufilla.com>
Reviewed-by: Eugen Hristev <eugen.hristev@microchip.com>

diff --git a/arch/arm/mach-at91/arm926ejs/lowlevel_init.S b/arch/arm/mach-at91/arm926ejs/lowlevel_init.S
index 71d7582..994f42e 100644 (file)
--- 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: