Hi,
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 if the reset function is a
C function.
The following patch changes to using r14+r15 instead of r6+r7 and
saves all necessary registers on the stack.
As I'm quite fresh to PowerPC assembly language I would appreciate
any feedback on the implementation.
On a side note, one could wonder why this function is not written in
C language to start with.
Best regards,
Mats Kärrman
--- a/arch/powerpc/lib/ticks.S
+++ b/arch/powerpc/lib/ticks.S
@@ -50,19 +50,24 @@ wait_ticks:
stwu r1, -16(r1)
mflr r0 /* save link register */
stw r0, 20(r1) /* Use r0 or GDB will be unhappy */
- mr r7, r3 /* save tick count */
+ stw r14, 12(r1) /* save used registers */
+ stw r15, 8(r1)
+ mr r14, r3 /* save tick count */
bl get_ticks /* Get start time */
/* Calculate end time */
- addc r7, r4, r7 /* Compute end time lower */
- addze r6, r3 /* and end time upper */
+ addc r14, r4, r14 /* Compute end time lower */
+ addze r15, r3 /* and end time upper */
WATCHDOG_RESET /* Trigger watchdog, if needed */
1: bl get_ticks /* Get current time */
- subfc r4, r4, r7 /* Subtract current time from end time */
- subfe. r3, r3, r6
+ subfc r4, r4, r14 /* Subtract current time from end time */
+ subfe. r3, r3, r15
bge 1b /* Loop until time expired */
- mtlr r0 /* restore link register */
+ lwz r15, 8(r1) /* restore saved registers */
+ lwz r14, 12(r1)
+ lwz r0, 20(r1)
addi r1,r1,16
+ mtlr r0
blr
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