Partial fix for a bug in rev.1.231. If suspend/resume clobbers the

RTC state, then it may clobber the RTC index register, so the index
register must be restored before using it to restore control registers
in rtc_restore().

The following problems remain:
- rtc_restore() is only called if pmtimer is configured.  Buggy
  suspend/resumes are more likely to clobber the index register than
  a control register, so pmtimer is more needed than it used to be.
- pmtimer doesn't exist for amd64.
- Restoring of the RTC state may race with rtcintr().  If an RTC
  interrupt is handled before the state is restored, then rtcin(RTC_INTR)
  in rtcintr() may read from the wrong register, so rtcintr() may spin
  forever.  This may be mitigated by the most common state clobbering
  being to turn off RTC interrupts.

2 files changed, 2 insertions, 0 deletions

diff --git a/sys/i386/isa/clock.c b/sys/i386/isa/clock.c
index f2de4f5..3125bd1 100644
--- a/sys/i386/isa/clock.c
+++ b/sys/i386/isa/clock.c
@@ -579,6 +579,7 @@ rtc_restore(void)
 
 	/* Restore all of the RTC's "status" (actually, control) registers. */
 	/* XXX locking is needed for RTC access. */
+	rtc_reg = -1;
 	writertc(RTC_STATUSB, RTCSB_24HR);
 	writertc(RTC_STATUSA, rtc_statusa);
 	writertc(RTC_STATUSB, rtc_statusb);
diff --git a/sys/isa/atrtc.c b/sys/isa/atrtc.c
index f2de4f5..3125bd1 100644
--- a/sys/isa/atrtc.c
+++ b/sys/isa/atrtc.c
@@ -579,6 +579,7 @@ rtc_restore(void)
 
 	/* Restore all of the RTC's "status" (actually, control) registers. */
 	/* XXX locking is needed for RTC access. */
+	rtc_reg = -1;
 	writertc(RTC_STATUSB, RTCSB_24HR);
 	writertc(RTC_STATUSA, rtc_statusa);
 	writertc(RTC_STATUSB, rtc_statusb);