/*
 * Tock is an abstract clock.  It counts from 0 to MAX_TOCKS and
 * back to 0 again.  Typically tick is a free-running count register.
 *
 * At any time, one alarm can be set anywhere inside [0, MAX_TOCKS].
 * Once tock reaches the set value, an interrupt happens and a callback
 * routine, tock_expire(), is called.
 *
 * A pending alarm can be replaced by a new alarm.
 *
 * A seoncd interrupt is not required to happen after the alarm expires
 * and if no new alarm is set.
 *
 * Typically tock alarm is implemented with a hardware timer.
 *
 * Optionally the tock can support an additional periodic alarm.  This is
 * useful for slightly more efficient support of the legacy jiffies.
 * Typically a second hardware timer is used in implementation.
 *
 * <asm/tock.h> must define the following:
 *
 * . define tock_t
 * 	e.g., typedef unsigned int tock_t
 *
 * . define signed_tock_t (for elapsed time in tocks)
 * 	e.g., typedef int signed_tock_t
 *
 * . define MAX_TOCKS - valid tocks is between 0 and MAX_TOCKS, inclusive
 * 	MAX_TOCKS should be (tock_t)-1.
 *
 * . (optionally) define tock_before/after
 * 	tock_before(a,b)
 * 	tock_after(a,b)
 * 	tock_before_eq(a,b)
 * 	tock_after_eq(a,b)
 * 	#define	HAS_TICK_COMPARISON
 *
 * . tock_t get_tocks(void) 
 * 	- return current tick read
 *
 * . singed_tock_t tock_to_nsec(singed_tock_t)
 * . singed_tock_t nsec_to_tock(singed_tock_t)	 
 * 	- note, type is singed_tock_t, can be negative
 *
 * . int schedule_next_alarm(tock_t t)
 * 	- return non-zero to indicate the time has passed t.
 * 	  return 0 to indiciate an interrupt has been scheduled
 * 	  Called with interrupt turned off
 *
 * . int support_periodic_alarm(void)
 * 	- return non-zero if we can set up schedule_periodic alarm
 *
 * . int schedule_periodic_alarm(tock_t delay, tock_t period)
 * 	- set up a periodic alarm.  It should not skew w.r.t. to tock counts.
 */

#include <asm/tock.h>


#ifndef HAS_TICK_COMPARISON
#define tock_after(a,b)         \
        (typecheck(tock_t, a) && \
         typecheck(tock_t, b) && \
         ((singed_tock_t)(b) - (singed_tock_t)(a) < 0))
#define tock_before(a,b)        tock_after(b,a)

#define tock_after_eq(a,b)      \
        (typecheck(tock_t, a) && \
         typecheck(tock_t, b) && \
         ((singed_tock_t)(a) - (singed_tock_t)(b) >= 0))
#define tock_before_eq(a,b)     tock_after_eq(b,a)

#define tock_round(a)		(a)
#endif	/* HAS_TICK_COMPARISON */

/*
 * call this routine when tock alarm expires.  Periodic indicates whether
 * the interrupt is caused solely by periodic alarm or not.
 */
asmlinkage void tock_expire(struct pt_regs *regs, int periodic);