- Add a workaround for a bug in BlackBird CPUs (said to be part of the

  SpitFire erratum #54) which can cause writes to the TICK_CMPR register
  to fail. This seems to fix the dying clocks problem reported by jhb@
  and kris@. [1]
- In tick_start() don't reset the tick counter of the boot processor to
  zero. It's initially reset in _start() and afterwards but _before_
  tick_start() is called on the BSP the APs synchronise with the tick
  counter of the BSP in mp_startup(). Resetting the tick counter of the
  BSP in tick_start() probably also was the cause of problems seen when
  using the CPU tick counter as timecounter on SMP machines.
  Not resetting the tick counter of the BSP in mp_startup() makes the
  tick counters and tick interrupts between the BSP and APs be pretty
  much in sync as it's supposed to be. This also means there's no longer
  a real reason to have separate tick_start() and tick_start_ap() so
  merge them and zap tick_start_ap(). This is also a first step in
  simplifying the interface to the tick counters in preparation to use
  alternate clock hardware where available.
- Switch to the algorithm used on FreeBSD/ia64 for updating the tick
  interrupt register and which compensates the clock drift caused by
  varying delays between when the tick interrupts actually trigger and
  when they are serviced. Not compensating the clock drift mainly hurts
  interactive performance especially when using WITNESS. [2]
  For further information about the algorithm also see the commit log
  of sys/ia64/ia64/interrupt.c rev. 1.38.
  On sparc64 the sysctls for monitoring the behaviour of the tick
  interrupts are machdep.tick.adjust_edges, machdep.tick.adjust_excess,
  machdep.tick.adjust_missed and machdep.tick.adjust_ticks.
- In tick_init() just use tick_stop() for stopping the tick interrupts
  until a proper handler is set up later. This also stops the system
  tick interrupt on USIII systems earlier.
- In tick_start() check for a rough upper limit of HZ.
- Some minor changes, e.g. use FBSDID, remove unused headers, etc.

Info obtained from:	Linux [1]
Ok'ed by:		marcel [2]
Additional testing by:	kris (earlier version of the workaround), jhb
X-MFC after:		3 days [1]

3 files changed, 20 insertions, 8 deletions

diff --git a/sys/sparc64/include/cpufunc.h b/sys/sparc64/include/cpufunc.h
index 763741d..fc50e20 100644
--- a/sys/sparc64/include/cpufunc.h
+++ b/sys/sparc64/include/cpufunc.h
@@ -171,6 +171,23 @@ int fasword32(u_long asi, void *addr, uint32_t *val);
 	    : : "r" (val), "rI" (xor));					\
 } while (0)
 
+/*
+ * Macro intended to be used instead of wr(asr23, val, xor) for writing to
+ * the TICK_CMPR register in order to avoid a bug in BlackBird CPUs that
+ * can cause these writes to fail under certain condidtions which in turn
+ * causes the hardclock to stop. The workaround is to perform the write
+ * at the beginning of an I-Cache line directly followed by a dummy read.
+ */
+#define	wrtickcmpr(val, xor) ({						\
+	__asm __volatile(						\
+	"	ba,pt	%%xcc, 1f ;		"			\
+	"	 nop	 ;			"			\
+	"	.align	64 ;			"			\
+	"1:	wr	%0, %1, %%asr23 ;	"			\
+	"	rd	%%asr23, %%g0 ;		"			\
+	: : "r" (val), "rI" (xor));					\
+})
+
 static __inline void
 breakpoint(void)
 {
diff --git a/sys/sparc64/include/pcpu.h b/sys/sparc64/include/pcpu.h
index b854921..4e025c1 100644
--- a/sys/sparc64/include/pcpu.h
+++ b/sys/sparc64/include/pcpu.h
@@ -51,6 +51,8 @@ struct pmap;
 	struct	intr_request *pc_irfree;				\
 	struct 	pmap *pc_pmap;						\
 	vm_offset_t pc_addr;						\
+	u_long	pc_tickref;						\
+	u_long	pc_tickadj;						\
 	u_int 	pc_mid;							\
 	u_int	pc_node;						\
 	u_int	pc_tlb_ctx;						\
diff --git a/sys/sparc64/include/tick.h b/sys/sparc64/include/tick.h
index e317bd8..8586a0d 100644
--- a/sys/sparc64/include/tick.h
+++ b/sys/sparc64/include/tick.h
@@ -29,15 +29,8 @@
 #ifndef _MACHINE_TICK_H_
 #define	_MACHINE_TICK_H_
 
-typedef void tick_func_t(struct clockframe *);
-
 void	tick_init(u_long clock);
-void	tick_start(tick_func_t *func);
-#ifdef SMP
-void	tick_start_ap(void);
-#endif
+void	tick_start(void);
 void	tick_stop(void);
 
-tick_func_t tick_hardclock;
-
 #endif