[U-Boot] [PATCH] powerpc/lib: fix unsafe register handling in wait_ticks

[Stefan Roese <sr@denx.de>]

On 01/27/2013 06:03 PM, Mats K?rrman wrote:
> If watchdog is enabled, the arch/powerpc/lib/ticks.S::wait_ticks() function
> calls the function specified by the WATCHDOG_RESET macro.
> The wait_ticks function depends on the registers r0, r6 and r7 being
> preserved however that is not guaranteed, e.g. if the reset function is a
> C function this will probably overwrite r0 and cause an endless loop.
> 
> The following patch changes to using r14+r15 instead of r6+r7 (to resemble
> what would have been generated by a C compiler) and saves all necessary
> registers on the stack.
> 
> The patch has been tested on a custom MPC5125 based machine using the 512x
> powerpc architecture.
> 
> Signed-off-by: Mats Karrman <mats.karrman@tritech.se>
> Cc: Wolfgang Denk <wd@denx.de>
> Acked-by: Joakim Tjernlund <joakim.tjernlund@transmode.se>

Thanks for this fix. I just reproduced this problem on another MPC5200
based board (a4m2k) while implementing watchdog support. And this patch
fixes the problem (hangup in wait_ticks).

So:

Tested-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan