timekeeping: Create struct tk_read_base and use it in struct timekeeper

The members of the new struct are the required ones for the new NMI
safe accessor to clcok monotonic. In order to reuse the existing
timekeeping code and to make the update of the fast NMI safe
timekeepers a simple memcpy use the struct for the timekeeper as well
and convert all users.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>

1 files changed, 55 insertions, 48 deletions

diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h
index 75bb8add78f5..97381997625b 100644
--- a/include/linux/timekeeper_internal.h
+++ b/include/linux/timekeeper_internal.h
@@ -10,80 +10,87 @@
 #include <linux/jiffies.h>
 #include <linux/time.h>
 
-/*
- * Structure holding internal timekeeping values.
- *
- * Note: wall_to_monotonic is what we need to add to xtime (or xtime
- * corrected for sub jiffie times) to get to monotonic time.
- * Monotonic is pegged at zero at system boot time, so
- * wall_to_monotonic will be negative, however, we will ALWAYS keep
- * the tv_nsec part positive so we can use the usual normalization.
+/**
+ * struct tk_read_base - base structure for timekeeping readout
+ * @clock:      Current clocksource used for timekeeping.
+ * @read:       Read function of @clock
+ * @mask:       Bitmask for two's complement subtraction of non 64bit clocks
+ * @cycle_last: @clock cycle value at last update
+ * @mult:       NTP adjusted multiplier for scaled math conversion
+ * @shift:      Shift value for scaled math conversion
+ * @xtime_nsec: Shifted (fractional) nano seconds offset for readout
+ * @base_mono:  ktime_t (nanoseconds) base time for readout
  *
- * wall_to_monotonic is moved after resume from suspend for the
- * monotonic time not to jump. To calculate the real boot time offset
- * we need to do offs_real - offs_boot.
+ * This struct has size 56 byte on 64 bit. Together with a seqcount it
+ * occupies a single 64byte cache line.
  *
- * - wall_to_monotonic is no longer the boot time, getboottime must be
- * used instead.
+ * The struct is separate from struct timekeeper as it is also used
+ * for a fast NMI safe accessor to clock monotonic.
  */
-struct timekeeper {
-        /* Current clocksource used for timekeeping. */
+struct tk_read_base {
         struct clocksource      *clock;
-        /* Read function of @clock */
         cycle_t                 (*read)(struct clocksource *cs);
-        /* Bitmask for two's complement subtraction of non 64bit counters */
         cycle_t                 mask;
-        /* Last cycle value */
         cycle_t                 cycle_last;
-        /* NTP adjusted clock multiplier */
         u32                     mult;
-        /* The shift value of the current clocksource. */
         u32                     shift;
-        /* Clock shifted nano seconds */
         u64                     xtime_nsec;
-
-        /* Monotonic base time */
         ktime_t                 base_mono;
+};
 
-        /* Current CLOCK_REALTIME time in seconds */
+/**
+ * struct timekeeper - Structure holding internal timekeeping values.
+ * @tkr:                The readout base structure
+ * @xtime_sec:          Current CLOCK_REALTIME time in seconds
+ * @wall_to_monotonic:  CLOCK_REALTIME to CLOCK_MONOTONIC offset
+ * @offs_real:          Offset clock monotonic -> clock realtime
+ * @offs_boot:          Offset clock monotonic -> clock boottime
+ * @offs_tai:           Offset clock monotonic -> clock tai
+ * @tai_offset:         The current UTC to TAI offset in seconds
+ * @base_raw:           Monotonic raw base time in ktime_t format
+ * @raw_time:           Monotonic raw base time in timespec64 format
+ * @cycle_interval:     Number of clock cycles in one NTP interval
+ * @xtime_interval:     Number of clock shifted nano seconds in one NTP
+ *                      interval.
+ * @xtime_remainder:    Shifted nano seconds left over when rounding
+ *                      @cycle_interval
+ * @raw_interval:       Raw nano seconds accumulated per NTP interval.
+ * @ntp_error:          Difference between accumulated time and NTP time in ntp
+ *                      shifted nano seconds.
+ * @ntp_error_shift:    Shift conversion between clock shifted nano seconds and
+ *                      ntp shifted nano seconds.
+ *
+ * Note: For timespec(64) based interfaces wall_to_monotonic is what
+ * we need to add to xtime (or xtime corrected for sub jiffie times)
+ * to get to monotonic time.  Monotonic is pegged at zero at system
+ * boot time, so wall_to_monotonic will be negative, however, we will
+ * ALWAYS keep the tv_nsec part positive so we can use the usual
+ * normalization.
+ *
+ * wall_to_monotonic is moved after resume from suspend for the
+ * monotonic time not to jump. We need to add total_sleep_time to
+ * wall_to_monotonic to get the real boot based time offset.
+ *
+ * wall_to_monotonic is no longer the boot time, getboottime must be
+ * used instead.
+ */
+struct timekeeper {
+        struct tk_read_base     tkr;
         u64                     xtime_sec;
-        /* CLOCK_REALTIME to CLOCK_MONOTONIC offset */
         struct timespec64       wall_to_monotonic;
-
-        /* Offset clock monotonic -> clock realtime */
         ktime_t                 offs_real;
-        /* Offset clock monotonic -> clock boottime */
         ktime_t                 offs_boot;
-        /* Offset clock monotonic -> clock tai */
         ktime_t                 offs_tai;
-
-        /* The current UTC to TAI offset in seconds */
         s32                     tai_offset;
-
-        /* Monotonic raw base time */
         ktime_t                 base_raw;
-
-        /* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock. */
         struct timespec64       raw_time;
 
-        /* Number of clock cycles in one NTP interval. */
+        /* The following members are for timekeeping internal use */
         cycle_t                 cycle_interval;
-        /* Number of clock shifted nano seconds in one NTP interval. */
         u64                     xtime_interval;
-        /* shifted nano seconds left over when rounding cycle_interval */
         s64                     xtime_remainder;
-        /* Raw nano seconds accumulated per NTP interval. */
         u32                     raw_interval;
-
-        /*
-         * Difference between accumulated time and NTP time in ntp
-         * shifted nano seconds.
-         */
         s64                     ntp_error;
-        /*
-         * Shift conversion between clock shifted nano seconds and
-         * ntp shifted nano seconds.
-         */
         u32                     ntp_error_shift;
 };