[PATCH] x86/uv/time: set ->min_delta_ticks and ->max_delta_ticks

Nicolai Stange
2017-03-30T20:05:05Z

Currently, the x86's uv rtc clockevent device is initialized as follows:

clock_event_device_uv.min_delta_ns = NSEC_PER_SEC /
sn_rtc_cycles_per_second;
clock_event_device_uv.max_delta_ns = clocksource_uv.mask *
(NSEC_PER_SEC / sn_rtc_cycles_per_second);

This translates to a ->min_delta_ticks value of 1 and a ->max_delta_ticks
value of clocksource_uv.mask.

Initialize ->min_delta_ticks and ->max_delta_ticks with these values
respectively.

This patch alone doesn't introduce any change in functionality as the
clockevents core still looks exclusively at the (untouched) ->min_delta_ns
and ->max_delta_ns. As soon as this has changed, a followup patch will
purge the initialization of ->min_delta_ns and ->max_delta_ns from this
driver.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
---

Notes:
This prerequisite patch is part of a larger effort to feed NTP
corrections into the clockevent devices' frequencies and thus
avoiding their notion of time to diverge from the system's
one. If you're interested, the current state of the whole series
can be found at [1].

If you haven't got any objections and these prerequisites get
merged by 4.12 everywhere, I'll proceed with the remainder of
this series in 4.13.

Applicable to next-20170324 as well as to John' Stultz tree [2].

[1]
git://nicst.de/linux.git cev-freq-adj.v10.fortglx-4.12-time
https://nicst.de/git/?p=linux.git;a=shortlog;h=refs/heads/cev-freq-adj.v10.fortglx-4.12-time

[2]
https://git.linaro.org/people/john.stultz/linux.git fortglx/4.12/time

arch/x86/platform/uv/uv_time.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/arch/x86/platform/uv/uv_time.c b/arch/x86/platform/uv/uv_time.c
index 2ee7632d4916..b082d71b08ee 100644
--- a/arch/x86/platform/uv/uv_time.c
+++ b/arch/x86/platform/uv/uv_time.c
@@ -390,9 +390,11 @@ static __init int uv_rtc_setup_clock(void)

clock_event_device_uv.min_delta_ns = NSEC_PER_SEC /
sn_rtc_cycles_per_second;
+ clock_event_device_uv.min_delta_ticks = 1;

clock_event_device_uv.max_delta_ns = clocksource_uv.mask *
(NSEC_PER_SEC / sn_rtc_cycles_per_second);
+ clock_event_device_uv.max_delta_ticks = clocksource_uv.mask;

rc = schedule_on_each_cpu(uv_rtc_register_clockevents);
if (rc) {
--
2.12.0