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clockevents: Add direct ktime programming function 

There is at least one architecture (s390) with a sane clockevent device
that can be programmed with the equivalent of a ktime. No need to create
a delta against the current time, the ktime can be used directly.

A new clock device function 'set_next_ktime' is introduced that is called
with the unmodified ktime for the timer if the clock event device has the 
CLOCK_EVT_FEAT_KTIME bit set.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: john stultz <johnstul@us.ibm.com>
Link: http://lkml.kernel.org/r/20110823133142.815350967@de.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Martin Schwidefsky 2011-08-23 15:29:43 +02:00 committed by Thomas Gleixner
parent d1748302f7
commit 65516f8a7c
2 changed files with 11 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
include/linux/clockchips.h
View File

@ -45,20 +45,22 @@ enum clock_event_nofitiers {
*/
#define CLOCK_EVT_FEAT_PERIODIC 0x000001
#define CLOCK_EVT_FEAT_ONESHOT 0x000002
#define CLOCK_EVT_FEAT_KTIME 0x000004
/*
* x86(64) specific misfeatures:
*
* - Clockevent source stops in C3 State and needs broadcast support.
* - Local APIC timer is used as a dummy device.
*/
#define CLOCK_EVT_FEAT_C3STOP 0x000004
#define CLOCK_EVT_FEAT_DUMMY 0x000008
#define CLOCK_EVT_FEAT_C3STOP 0x000008
#define CLOCK_EVT_FEAT_DUMMY 0x000010
/**
* struct clock_event_device - clock event device descriptor
* @event_handler: Assigned by the framework to be called by the low
* level handler of the event source
* @set_next_event: set next event function
* @set_next_event: set next event function using a clocksource delta
* @set_next_ktime: set next event function using a direct ktime value
* @next_event: local storage for the next event in oneshot mode
* @max_delta_ns: maximum delta value in ns
* @min_delta_ns: minimum delta value in ns
@ -81,6 +83,8 @@ struct clock_event_device {
void (*event_handler)(struct clock_event_device *);
int (*set_next_event)(unsigned long evt,
struct clock_event_device *);
int (*set_next_ktime)(ktime_t expires,
struct clock_event_device *);
ktime_t next_event;
u64 max_delta_ns;
u64 min_delta_ns;

4
kernel/time/clockevents.c
View File

@ -216,6 +216,10 @@ int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
return 0;
/* Shortcut for clockevent devices that can deal with ktime. */
if (dev->features & CLOCK_EVT_FEAT_KTIME)
return dev->set_next_ktime(expires, dev);
delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
if (delta <= 0)
return force ? clockevents_program_min_delta(dev) : -ETIME;