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-rw-r--r--cpu/mpc8xx/interrupts.c20
1 files changed, 15 insertions, 5 deletions
diff --git a/cpu/mpc8xx/interrupts.c b/cpu/mpc8xx/interrupts.c
index 558dc09..20e7012 100644
--- a/cpu/mpc8xx/interrupts.c
+++ b/cpu/mpc8xx/interrupts.c
@@ -274,11 +274,21 @@ void timer_interrupt_cpu (struct pt_regs *regs)
/* Reset Timer Expired and Timers Interrupt Status */
immr->im_clkrstk.cark_plprcrk = KAPWR_KEY;
__asm__ ("nop");
-#ifdef CONFIG_MPC866_et_al
- immr->im_clkrst.car_plprcr |= PLPRCR_TEXPS;
-#else
- immr->im_clkrst.car_plprcr |= PLPRCR_TEXPS | PLPRCR_TMIST;
-#endif
+ /*
+ Clear TEXPS (and TMIST on older chips). SPLSS (on older
+ chips) is cleared too.
+
+ Bitwise OR is a read-modify-write operation so ALL bits
+ which are cleared by writing `1' would be cleared by
+ operations like
+
+ immr->im_clkrst.car_plprcr |= PLPRCR_TEXPS;
+
+ The same can be achieved by simple writing of the PLPRCR
+ to itself. If a bit value should be preserved, read the
+ register, ZERO the bit and write, not OR, the result back.
+ */
+ immr->im_clkrst.car_plprcr = immr->im_clkrst.car_plprcr;
}
/************************************************************************/