linux.git/arch/powerpc/kernel/time.c, branch v5.1

powerpc/kernel/time: Remove duplicate header

2019-01-30T12:42:31+00:00

Remove linux/rtc.h which is included more than once

Signed-off-by: Brajeswar Ghosh 
Signed-off-by: Michael Ellerman

powerpc/time: no steal_time when CONFIG_PPC_SPLPAR is not selected

2018-10-20T02:26:47+00:00

If CONFIG_PPC_SPLPAR is not selected, steal_time will always
be NUL, so accounting it is pointless

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman

powerpc/time: Only set CONFIG_ARCH_HAS_SCALED_CPUTIME on PPC64

2018-10-20T02:26:47+00:00

scaled cputime is only meaningfull when the processor has
SPURR and/or PURR, which means only on PPC64.

Removing it on PPC32 significantly reduces the size of
vtime_account_system() and vtime_account_idle() on an 8xx:

Before:
00000000 l     F .text	000000a8 vtime_delta
00000280 g     F .text	0000010c vtime_account_system
0000038c g     F .text	00000048 vtime_account_idle

After:
(vtime_delta gets inlined inside the two functions)
000001d8 g     F .text	000000a0 vtime_account_system
00000278 g     F .text	00000038 vtime_account_idle

In terms of performance, we also get approximatly 7% improvement on
task switch. The following small benchmark app is run with perf stat:

void *thread(void *arg)
{
	int i;

	for (i = 0; i < atoi((char*)arg); i++)
		pthread_yield();
}

int main(int argc, char **argv)
{
	pthread_t th1, th2;

	pthread_create(&th1, NULL, thread, argv[1]);
	pthread_create(&th2, NULL, thread, argv[1]);
	pthread_join(th1, NULL);
	pthread_join(th2, NULL);

	return 0;
}

Before the patch:

 Performance counter stats for 'chrt -f 98 ./sched 100000' (50 runs):

       8228.476465      task-clock (msec)         #    0.954 CPUs utilized            ( +-  0.23% )
            200004      context-switches          #    0.024 M/sec                    ( +-  0.00% )

After the patch:

 Performance counter stats for 'chrt -f 98 ./sched 100000' (50 runs):

       7649.070444      task-clock (msec)         #    0.955 CPUs utilized            ( +-  0.27% )
            200004      context-switches          #    0.026 M/sec                    ( +-  0.00% )

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman

powerpc/time: isolate scaled cputime accounting in dedicated functions.

2018-10-20T02:26:47+00:00

scaled cputime is only meaningfull when the processor has
SPURR and/or PURR, which means only on PPC64.

In preparation of the following patch that will remove
CONFIG_ARCH_HAS_SCALED_CPUTIME on PPC32, this patch moves
all scaled cputing accounting logic into dedicated functions.

This patch doesn't change any functionality. It's only code
reorganisation.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman

powerpc/time: Fix clockevent_decrementer initalisation for PR KVM

2018-10-19T04:09:04+00:00

In the recent commit 8b78fdb045de ("powerpc/time: Use
clockevents_register_device(), fixing an issue with large
decrementer") we changed the way we initialise the decrementer
clockevent(s).

We no longer initialise the mult & shift values of
decrementer_clockevent itself.

This has the effect of breaking PR KVM, because it uses those values
in kvmppc_emulate_dec(). The symptom is guest kernels spin forever
mid-way through boot.

For now fix it by assigning back to decrementer_clockevent the mult
and shift values.

Fixes: 8b78fdb045de ("powerpc/time: Use clockevents_register_device(), fixing an issue with large decrementer")
Signed-off-by: Michael Ellerman

powerpc/time: Add set_state_oneshot_stopped decrementer callback

2018-10-04T13:00:31+00:00

If CONFIG_PPC_WATCHDOG is enabled we always cap the decrementer to
0x7fffffff:

       if (IS_ENABLED(CONFIG_PPC_WATCHDOG))
                set_dec(0x7fffffff);
        else
                set_dec(decrementer_max);

If there are no future events, we don't reprogram the decrementer
after this and we end up with 0x7fffffff even on a large decrementer
capable system.

As suggested by Nick, add a set_state_oneshot_stopped callback
so we program the decrementer with decrementer_max if there are
no future events.

Signed-off-by: Anton Blanchard 
Signed-off-by: Michael Ellerman

powerpc/time: Use clockevents_register_device(), fixing an issue with large decrementer

2018-10-04T13:00:30+00:00

We currently cap the decrementer clockevent at 4 seconds, even on systems
with large decrementer support. Fix this by converting the code to use
clockevents_register_device() which calculates the upper bound based on
the max_delta passed in.

Signed-off-by: Anton Blanchard 
Signed-off-by: Michael Ellerman

powerpc/time: inline arch_vtime_task_switch()

2018-06-03T14:39:20+00:00

arch_vtime_task_switch() is a small function which is called
only from vtime_common_task_switch(), so it is worth inlining

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman

powerpc: remove unused to_tm() helper

2018-06-03T10:43:34+00:00

to_tm() is now completely unused, the only reference being in the
_dump_time() helper that is also unused. This removes both, leaving
the rest of the powerpc RTC code y2038 safe to as far as the hardware
supports.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Michael Ellerman

powerpc: use time64_t in update_persistent_clock

2018-06-03T10:43:34+00:00

update_persistent_clock() is deprecated because it suffers from overflow
in 2038 on 32-bit architectures. This changes powerpc to use the
update_persistent_clock64() replacement, and to pass down 64-bit
timestamps consistently.

This is now simpler, as we no longer have to worry about the offset
numbers in tm_year and tm_mon that are different between the Linux
conventions and RTAS.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Michael Ellerman