Bug fix from Gunter Magin <magin@@skil.camelot.de>:

    in libcpu/powerpc/mpc860/clock/clock.c:InstallClock() the reload value for
    the PIT is defined as:

      pit_value = (BSP_Configuration.microseconds_per_tick *
                 Cpu_table.clicks_per_usec) - 1 ;

    What exactly is a tick, and what is a click?

    My confusion stems from the fact, that Jay defines clicks_per_usec to 1
    which is correct for his configuration, where a 4MHz clock is predivided
    by 4 and then fed to the PIT. So I assume a "click" is just the period of
    the PIT input frequency.

    However, our HW config seems to have 32.768 kHz crystal input for PIT.
    Mandatory division by 4 means 8.196kHz (122usec) at the PIT.

    I think, the above assignment should read:

      pit_value = (BSP_Configuration.microseconds_per_tick /
                 Cpu_table.clicks_per_usec) - 1;

    where I can define Cpu_table.clicks_per_usec in bspstart.c to 122
    (clicks_per_usec). That would lead to a PIT reload value of
    10000/122 - 1 = 81 to reach a 10ms "tick" period.

1 files changed, 1 insertions, 1 deletions

diff --git a/c/src/lib/libcpu/powerpc/mpc821/clock/clock.c b/c/src/lib/libcpu/powerpc/mpc821/clock/clock.c
index 6aa88d36e3..bf11c9bcbb 100644
--- a/c/src/lib/libcpu/powerpc/mpc821/clock/clock.c
+++ b/c/src/lib/libcpu/powerpc/mpc821/clock/clock.c
@@ -74,7 +74,7 @@ void Install_clock(rtems_isr_entry clock_isr)
   
   Clock_driver_ticks = 0;
   
-  pit_value = BSP_Configuration.microseconds_per_tick *
+  pit_value = BSP_Configuration.microseconds_per_tick /
                Cpu_table.clicks_per_usec;
   if (pit_value == 0) {
     pit_value = 0xffff;