[PATCH] fix IBM cyclone clock and some cleanup

 - fix broken IBM cyclone time interpolator support
 - add support for cyclic timers through an addition of a mask
   in the timer interpolator structure
 - Allow time_interpolator_update() and time_interpolator_get_offset()
   to be invoked without an active time interpolator
   (necessary since the cyclone clock is initialized late in ACPI
   processing)
 - remove obsolete function time_interpolator_resolution()
 - add a mask to all struct time_interpolator setups in the
   kernel
 - Make time interpolators work on 32bit platforms
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Documentation/time_interpolators.txt

@@ -9,32 +9,33 @@ The architecture specific code typically provides gettimeofday and
 settimeofday under Linux. The time interpolator provides both if an arch
 defines CONFIG_TIME_INTERPOLATION. The arch still must set up timer tick
 operations and call the necessary functions to advance the clock.
+
 With the time interpolator a standardized interface exists for time
-interpolation between ticks which also allows the determination
-of time in a hardware independent way. The provided logic is highly scalable
+interpolation between ticks. The provided logic is highly scalable
 and has been tested in SMP situations of up to 512 CPUs.
 
 If CONFIG_TIME_INTERPOLATION is defined then the architecture specific code
-(or the device drivers - like HPET) must register time interpolators.
+(or the device drivers - like HPET) may register time interpolators.
 These are typically defined in the following way:
 
-static struct time_interpolator my_interpolator;
+static struct time_interpolator my_interpolator {
+	.frequency = MY_FREQUENCY,
+	.source = TIME_SOURCE_MMIO32,
+	.shift = 8,		/* scaling for higher accuracy */
+	.drift = -1,		/* Unknown drift */
+	.jitter = 0		/* time source is stable */
+};
 
 void time_init(void)
 {
 	....
 	/* Initialization of the timer *.
-	my_interpolator.frequency = MY_FREQUENCY;
-	my_interpolator.source = TIME_SOURCE_MMIO32;
 	my_interpolator.address = &my_timer;
-	my_interpolator.shift = 32;		/* increase accuracy of scaling */
-	my_interpolator.drift = -1;		/* Unknown */
-	my_interpolator.jitter = 0;		/* A stable time source */
 	register_time_interpolator(&my_interpolator);
 	....
 }
 
-For more details see include/linux/timex.h.
+For more details see include/linux/timex.h and kernel/timer.c.
 
-Christoph Lameter <christoph@lameter.com>, September 8, 2004
+Christoph Lameter <christoph@lameter.com>, October 31, 2004
 

arch/ia64/kernel/asm-offsets.c

@@ -217,6 +217,7 @@ void foo(void)
 	DEFINE(IA64_TIME_INTERPOLATOR_LAST_CYCLE_OFFSET, offsetof (struct time_interpolator, last_cycle));
 	DEFINE(IA64_TIME_INTERPOLATOR_LAST_COUNTER_OFFSET, offsetof (struct time_interpolator, last_counter));
 	DEFINE(IA64_TIME_INTERPOLATOR_JITTER_OFFSET, offsetof (struct time_interpolator, jitter));
+	DEFINE(IA64_TIME_INTERPOLATOR_MASK_OFFSET, offsetof (struct time_interpolator, mask));
 	DEFINE(IA64_TIME_SOURCE_CPU, TIME_SOURCE_CPU);
 	DEFINE(IA64_TIME_SOURCE_MMIO64, TIME_SOURCE_MMIO64);
 	DEFINE(IA64_TIME_SOURCE_MMIO32, TIME_SOURCE_MMIO32);

arch/ia64/kernel/cyclone.c

@@ -19,10 +19,11 @@ void __init cyclone_setup(void)
 
 
 struct time_interpolator cyclone_interpolator = {
-	.source =	TIME_SOURCE_MMIO32,
-	.shift =	32,
+	.source =	TIME_SOURCE_MMIO64,
+	.shift =	16,
 	.frequency =	CYCLONE_TIMER_FREQ,
 	.drift =	-100,
+	.mask =		(1LL << 40) - 1
 };
 
 int __init init_cyclone_clock(void)

arch/ia64/kernel/fsys.S

@@ -177,7 +177,7 @@ ENTRY(fsys_gettimeofday)
 	// r11 = preserved: saved ar.pfs
 	// r12 = preserved: memory stack
 	// r13 = preserved: thread pointer
-	// r14 = debug pointer / usable
+	// r14 = address of mask / mask
 	// r15 = preserved: system call number
 	// r16 = preserved: current task pointer
 	// r17 = wall to monotonic use
@@ -226,7 +226,6 @@ ENTRY(fsys_gettimeofday)
 	add r10 = IA64_TIME_INTERPOLATOR_ADDRESS_OFFSET,r20
 	extr r3 = r21,32,32	// time_interpolator->nsec_per_cyc
 	extr r8 = r21,0,16	// time_interpolator->source
-	nop.i 123
 	cmp.ne p6, p0 = 0, r2	// Fallback if work is scheduled
 (p6)    br.cond.spnt.many fsys_fallback_syscall
 	;;
@@ -257,17 +256,20 @@ ENTRY(fsys_gettimeofday)
 	add r24 = IA64_TIME_INTERPOLATOR_OFFSET_OFFSET,r20
 (p15)	ld8 r17 = [r19],IA64_TIMESPEC_TV_NSEC_OFFSET
  	ld8 r9 = [r27],IA64_TIMESPEC_TV_NSEC_OFFSET
-	nop.i 123
+	add r14 = IA64_TIME_INTERPOLATOR_MASK_OFFSET, r20
 	;;
 	ld8 r18 = [r24]		// time_interpolator->offset
 	ld8 r8 = [r27],-IA64_TIMESPEC_TV_NSEC_OFFSET	// xtime.tv_nsec
 (p13)	sub r3 = r25,r2	// Diff needed before comparison (thanks davidm)
 	;;
+	ld8 r14 = [r14]		// time_interpolator->mask
 (p13)	cmp.gt.unc p6,p7 = r3,r0	// check if it is less than last. p6,p7 cleared
 	sub r10 = r2,r26	// current_counter - last_counter
 	;;
 (p6)	sub r10 = r25,r26	// time we got was less than last_cycle
 (p7)	mov ar.ccv = r25	// more than last_cycle. Prep for cmpxchg
+	;;
+	and r10 = r10,r14	// Apply mask
 	;;
 	setf.sig f8 = r10
 	nop.i 123

arch/ia64/kernel/time.c

@@ -45,7 +45,11 @@ EXPORT_SYMBOL(last_cli_ip);
 
 #endif
 
-static struct time_interpolator itc_interpolator;
+static struct time_interpolator itc_interpolator = {
+	.shift = 16,
+	.mask = 0xffffffffffffffffLL,
+	.source = TIME_SOURCE_CPU
+};
 
 static irqreturn_t
 timer_interrupt (int irq, void *dev_id, struct pt_regs *regs)
@@ -206,9 +210,7 @@ ia64_init_itm (void)
 
 	if (!(sal_platform_features & IA64_SAL_PLATFORM_FEATURE_ITC_DRIFT)) {
 		itc_interpolator.frequency = local_cpu_data->itc_freq;
-		itc_interpolator.shift = 16;
 		itc_interpolator.drift = itc_drift;
-		itc_interpolator.source = TIME_SOURCE_CPU;
 #ifdef CONFIG_SMP
 		/* On IA64 in an SMP configuration ITCs are never accurately synchronized.
 		 * Jitter compensation requires a cmpxchg which may limit
@@ -222,7 +224,6 @@ ia64_init_itm (void)
 		 */
 		if (!nojitter) itc_interpolator.jitter = 1;
 #endif
-		itc_interpolator.addr = NULL;
 		register_time_interpolator(&itc_interpolator);
 	}
 

arch/ia64/sn/kernel/sn2/timer.c

@@ -22,14 +22,16 @@
 
 extern unsigned long sn_rtc_cycles_per_second;
 
-static struct time_interpolator sn2_interpolator;
+static struct time_interpolator sn2_interpolator = {
+	.drift = -1,
+	.shift = 10,
+	.mask = (1LL << 55) - 1,
+	.source = TIME_SOURCE_MMIO64,
+	.addr = RTC_COUNTER_ADDR
+};
 
 void __init sn_timer_init(void)
 {
 	sn2_interpolator.frequency = sn_rtc_cycles_per_second;
-	sn2_interpolator.drift = -1;	/* unknown */
-	sn2_interpolator.shift = 10;	/* RTC is 54 bits maximum shift is 10 */
-	sn2_interpolator.addr = RTC_COUNTER_ADDR;
-	sn2_interpolator.source = TIME_SOURCE_MMIO64;
 	register_time_interpolator(&sn2_interpolator);
 }

arch/sparc64/kernel/time.c

@@ -1046,6 +1046,7 @@ static struct notifier_block sparc64_cpufreq_notifier_block = {
 static struct time_interpolator sparc64_cpu_interpolator = {
 	.source		=	TIME_SOURCE_CPU,
 	.shift		=	16,
+	.mask		=	0xffffffffffffffffLL
 };
 
 /* The quotient formula is taken from the IA64 port. */

drivers/char/hpet.c

@@ -664,7 +664,8 @@ int hpet_control(struct hpet_task *tp, unsigned int cmd, unsigned long arg)
 
 static struct time_interpolator hpet_interpolator = {
 	.source = TIME_SOURCE_MMIO64,
-	.shift = 10
+	.shift = 10,
+	.mask = 0xffffffffffffffffLL
 };
 
 #endif

include/linux/timex.h

@@ -285,20 +285,18 @@ extern long pps_stbcnt;		/* stability limit exceeded */
  * for the compensation is that the timer routines are not as scalable anymore.
  */
 
-#define INTERPOLATOR_ADJUST 65536
-#define INTERPOLATOR_MAX_SKIP 10*INTERPOLATOR_ADJUST
-
 struct time_interpolator {
-	unsigned short source;		/* time source flags */
-	unsigned char shift;		/* increases accuracy of multiply by shifting. */
-			/* Note that bits may be lost if shift is set too high */
-	unsigned char jitter;		/* if set compensate for fluctuations */
-	unsigned nsec_per_cyc;		/* set by register_time_interpolator() */
+	u16 source;			/* time source flags */
+	u8 shift;			/* increases accuracy of multiply by shifting. */
+				/* Note that bits may be lost if shift is set too high */
+	u8 jitter;			/* if set compensate for fluctuations */
+	u32 nsec_per_cyc;		/* set by register_time_interpolator() */
 	void *addr;			/* address of counter or function */
+	u64 mask;			/* mask the valid bits of the counter */
 	unsigned long offset;		/* nsec offset at last update of interpolator */
-	unsigned long last_counter;	/* counter value in units of the counter at last update */
-	unsigned long last_cycle;	/* Last timer value if TIME_SOURCE_JITTER is set */
-	unsigned long frequency;	/* frequency in counts/second */
+	u64 last_counter;		/* counter value in units of the counter at last update */
+	u64 last_cycle;			/* Last timer value if TIME_SOURCE_JITTER is set */
+	u64 frequency;			/* frequency in counts/second */
 	long drift;			/* drift in parts-per-million (or -1) */
 	unsigned long skips;		/* skips forward */
 	unsigned long ns_skipped;	/* nanoseconds skipped */
@@ -308,7 +306,6 @@ struct time_interpolator {
 extern void register_time_interpolator(struct time_interpolator *);
 extern void unregister_time_interpolator(struct time_interpolator *);
 extern void time_interpolator_reset(void);
-extern unsigned long time_interpolator_resolution(void);
 extern unsigned long time_interpolator_get_offset(void);
 
 #else /* !CONFIG_TIME_INTERPOLATION */

kernel/timer.c

@@ -1438,7 +1438,7 @@ struct time_interpolator *time_interpolator;
 static struct time_interpolator *time_interpolator_list;
 static spinlock_t time_interpolator_lock = SPIN_LOCK_UNLOCKED;
 
-static inline unsigned long time_interpolator_get_cycles(unsigned int src)
+static inline u64 time_interpolator_get_cycles(unsigned int src)
 {
 	unsigned long (*x)(void);
 
@@ -1453,23 +1453,25 @@ static inline unsigned long time_interpolator_get_cycles(unsigned int src)
 
 		case TIME_SOURCE_MMIO32	:
 			return readl(time_interpolator->addr);
+
 		default: return get_cycles();
 	}
 }
 
-static inline unsigned long time_interpolator_get_counter(void)
+static inline u64 time_interpolator_get_counter(void)
 {
 	unsigned int src = time_interpolator->source;
 
 	if (time_interpolator->jitter)
 	{
-		unsigned long lcycle;
-		unsigned long now;
+		u64 lcycle;
+		u64 now;
 
 		do {
 			lcycle = time_interpolator->last_cycle;
 			now = time_interpolator_get_cycles(src);
-			if (lcycle && time_after(lcycle, now)) return lcycle;
+			if (lcycle && time_after(lcycle, now))
+				return lcycle;
 			/* Keep track of the last timer value returned. The use of cmpxchg here
 			 * will cause contention in an SMP environment.
 			 */
@@ -1486,26 +1488,29 @@ void time_interpolator_reset(void)
 	time_interpolator->last_counter = time_interpolator_get_counter();
 }
 
-unsigned long time_interpolator_resolution(void)
-{
-	if (time_interpolator->frequency < NSEC_PER_SEC)
-		return NSEC_PER_SEC / time_interpolator->frequency;
-	else
-		return 1;
-}
-
-#define GET_TI_NSECS(count,i) ((((count) - i->last_counter) * i->nsec_per_cyc) >> i->shift)
+#define GET_TI_NSECS(count,i) (((((count) - i->last_counter) & (i)->mask) * (i)->nsec_per_cyc) >> (i)->shift)
 
 unsigned long time_interpolator_get_offset(void)
 {
+	/* If we do not have a time interpolator set up then just return zero */
+	if (!time_interpolator)
+		return 0;
+
 	return time_interpolator->offset +
 		GET_TI_NSECS(time_interpolator_get_counter(), time_interpolator);
 }
 
+#define INTERPOLATOR_ADJUST 65536
+#define INTERPOLATOR_MAX_SKIP 10*INTERPOLATOR_ADJUST
+
 static void time_interpolator_update(long delta_nsec)
 {
-	unsigned long counter = time_interpolator_get_counter();
-	unsigned long offset = time_interpolator->offset + GET_TI_NSECS(counter, time_interpolator);
+	u64 counter;
+	unsigned long offset;
+
+	/* If there is no time interpolator set up then do nothing */
+	if (!time_interpolator)
+		return;
 
 	/* The interpolator compensates for late ticks by accumulating
          * the late time in time_interpolator->offset. A tick earlier than
@@ -1515,6 +1520,9 @@ static void time_interpolator_update(long delta_nsec)
 	 * and the tuning logic insures that.
          */
 
+	counter = time_interpolator_get_counter();
+	offset = time_interpolator->offset + GET_TI_NSECS(counter, time_interpolator);
+
 	if (delta_nsec < 0 || (unsigned long) delta_nsec < offset)
 		time_interpolator->offset = offset - delta_nsec;
 	else {
@@ -1553,7 +1561,11 @@ register_time_interpolator(struct time_interpolator *ti)
 {
 	unsigned long flags;
 
-	ti->nsec_per_cyc = (NSEC_PER_SEC << ti->shift) / ti->frequency;
+	/* Sanity check */
+	if (ti->frequency == 0 || ti->mask == 0)
+		BUG();
+
+	ti->nsec_per_cyc = ((u64)NSEC_PER_SEC << ti->shift) / ti->frequency;
 	spin_lock(&time_interpolator_lock);
 	write_seqlock_irqsave(&xtime_lock, flags);
 	if (is_better_time_interpolator(ti)) {