From 02ecee07ca30f76f2a0f1381661a688b8e501ab0 Mon Sep 17 00:00:00 2001 From: Lakshmi Sowjanya D Date: Mon, 13 May 2024 16:08:10 +0530 Subject: timekeeping: Add function to convert realtime to base clock PPS (Pulse Per Second) generates a hardware pulse every second based on CLOCK_REALTIME. This works fine when the pulse is generated in software from a hrtimer callback function. For hardware which generates the pulse by programming a timer it is required to convert CLOCK_REALTIME to the underlying hardware clock. The X86 Timed IO device is based on the Always Running Timer (ART), which is the base clock of the TSC, which is usually the system clocksource on X86. The core code already has functionality to convert base clock timestamps to system clocksource timestamps, but there is no support for converting the other way around. Provide the required functionality to support such devices in a generic way to avoid code duplication in drivers: 1) ktime_real_to_base_clock() to convert a CLOCK_REALTIME timestamp to a base clock timestamp 2) timekeeping_clocksource_has_base() to allow drivers to validate that the system clocksource is based on a particular clocksource ID. [ tglx: Simplify timekeeping_clocksource_has_base() and add missing READ_ONCE() ] Co-developed-by: Thomas Gleixner Signed-off-by: Thomas Gleixner Co-developed-by: Christopher S. Hall Signed-off-by: Christopher S. Hall Signed-off-by: Lakshmi Sowjanya D Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20240513103813.5666-10-lakshmi.sowjanya.d@intel.com --- include/linux/timekeeping.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux') diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h index b2ee182d891e..fc12a9ba2c88 100644 --- a/include/linux/timekeeping.h +++ b/include/linux/timekeeping.h @@ -318,6 +318,10 @@ struct system_counterval_t { bool use_nsecs; }; +extern bool ktime_real_to_base_clock(ktime_t treal, + enum clocksource_ids base_id, u64 *cycles); +extern bool timekeeping_clocksource_has_base(enum clocksource_ids id); + /* * Get cross timestamp between system clock and device clock */ -- cgit v1.2.3