Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
timekeeping: Provide time setter for auxiliary clocks
Add clock_settime(2) support for auxiliary clocks. The function affects the
AUX offset which is added to the "monotonic" clock readout of these clocks.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250625183757.995688714@linutronix.de
+44
+44
kernel/time/timekeeping.c
+44
kernel/time/timekeeping.c
···
2765
2765
return ktime_get_aux_ts64(id, tp) ? 0 : -ENODEV;
2766
2766
}
2767
2767
2768
+
static int aux_clock_set(const clockid_t id, const struct timespec64 *tnew)
2769
+
{
2770
+
struct tk_data *aux_tkd = aux_get_tk_data(id);
2771
+
struct timekeeper *aux_tks;
2772
+
ktime_t tnow, nsecs;
2773
+
2774
+
if (!timespec64_valid_settod(tnew))
2775
+
return -EINVAL;
2776
+
if (!aux_tkd)
2777
+
return -ENODEV;
2778
+
2779
+
aux_tks = &aux_tkd->shadow_timekeeper;
2780
+
2781
+
guard(raw_spinlock_irq)(&aux_tkd->lock);
2782
+
if (!aux_tks->clock_valid)
2783
+
return -ENODEV;
2784
+
2785
+
/* Forward the timekeeper base time */
2786
+
timekeeping_forward_now(aux_tks);
2787
+
/*
2788
+
* Get the updated base time. tkr_mono.base has not been
2789
+
* updated yet, so do that first. That makes the update
2790
+
* in timekeeping_update_from_shadow() redundant, but
2791
+
* that's harmless. After that @tnow can be calculated
2792
+
* by using tkr_mono::cycle_last, which has been set
2793
+
* by timekeeping_forward_now().
2794
+
*/
2795
+
tk_update_ktime_data(aux_tks);
2796
+
nsecs = timekeeping_cycles_to_ns(&aux_tks->tkr_mono, aux_tks->tkr_mono.cycle_last);
2797
+
tnow = ktime_add(aux_tks->tkr_mono.base, nsecs);
2798
+
2799
+
/*
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+
* Calculate the new AUX offset as delta to @tnow ("monotonic").
2801
+
* That avoids all the tk::xtime back and forth conversions as
2802
+
* xtime ("realtime") is not applicable for auxiliary clocks and
2803
+
* kept in sync with "monotonic".
2804
+
*/
2805
+
aux_tks->offs_aux = ktime_sub(timespec64_to_ktime(*tnew), tnow);
2806
+
2807
+
timekeeping_update_from_shadow(aux_tkd, TK_UPDATE_ALL);
2808
+
return 0;
2809
+
}
2810
+
2768
2811
const struct k_clock clock_aux = {
2769
2812
.clock_getres = aux_get_res,
2770
2813
.clock_get_timespec = aux_get_timespec,
2814
+
.clock_set = aux_clock_set,
2771
2815
};
2772
2816
2773
2817
static __init void tk_aux_setup(void)