[linuxsh-dev] SH-4 RTC

[NIIBE Y. <gn...@m1...>]

While implementing RTC routine in SH IPL+g:
--------------------------
static unsigned long get_tick_1 (void)
{
  unsigned int cnt128, sec, min, hour;

  while (1)
    {
      p4_outb (RCR1, 0);  /* Clear CF-bit */

      cnt128 = (p4_inb (R64CNT) ^ RTC_BIT_CHANGE);
      sec = p4_inb (RSECCNT);
      min = p4_inb (RMINCNT);
      hour = p4_inb (RHRCNT);

      if ((p4_inb (RCR1) & RCR1_CF) == 0)
      break;
    }

  BCD_TO_BIN(sec);
  BCD_TO_BIN(min);
  BCD_TO_BIN(hour);

  return cnt128 + 128*(sec+60*(min+60*hour));
}
--------------------------

I think I've found a hardware bug(? or feature) of SH-4.  I need to
set RTC_BIT_CHANGE as 0x40, to get the straight value of the tick.
Without this, the tick value goes backward(!) sometime.

I see no problem for SH7709A, so I set RTC_BIT_CHANGE as 0 on SH7709A.

If it's true, we need to fix our RTC related code.  Could you please
check your CPU?  How about chips by ST?

I've checked my CqREEK SH-4 and SolutionEngine SH7750 and
SolutionEngine SH7750S.  Both of SH7750 and SH7750S has this issue.
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