Commit 60ecc26e authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarJohn Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250625183757.995688714@linutronix.de
parent 606424bf

kernel/time/timekeeping.c

+44 −0
Original line number Diff line number Diff line
@@ -2765,9 +2765,53 @@ static int aux_get_timespec(clockid_t id, struct timespec64 *tp) 
	return ktime_get_aux_ts64(id, tp) ? 0 : -ENODEV;

}



static int aux_clock_set(const clockid_t id, const struct timespec64 *tnew)

{

	struct tk_data *aux_tkd = aux_get_tk_data(id);

	struct timekeeper *aux_tks;

	ktime_t tnow, nsecs;



	if (!timespec64_valid_settod(tnew))

		return -EINVAL;

	if (!aux_tkd)

		return -ENODEV;



	aux_tks = &aux_tkd->shadow_timekeeper;



	guard(raw_spinlock_irq)(&aux_tkd->lock);

	if (!aux_tks->clock_valid)

		return -ENODEV;



	/* Forward the timekeeper base time */

	timekeeping_forward_now(aux_tks);

	/*

	 * Get the updated base time. tkr_mono.base has not been

	 * updated yet, so do that first. That makes the update

	 * in timekeeping_update_from_shadow() redundant, but

	 * that's harmless. After that @tnow can be calculated

	 * by using tkr_mono::cycle_last, which has been set

	 * by timekeeping_forward_now().

	 */

	tk_update_ktime_data(aux_tks);

	nsecs = timekeeping_cycles_to_ns(&aux_tks->tkr_mono, aux_tks->tkr_mono.cycle_last);

	tnow = ktime_add(aux_tks->tkr_mono.base, nsecs);



	/*

	 * Calculate the new AUX offset as delta to @tnow ("monotonic").

	 * That avoids all the tk::xtime back and forth conversions as

	 * xtime ("realtime") is not applicable for auxiliary clocks and

	 * kept in sync with "monotonic".

	 */

	aux_tks->offs_aux = ktime_sub(timespec64_to_ktime(*tnew), tnow);



	timekeeping_update_from_shadow(aux_tkd, TK_UPDATE_ALL);

	return 0;

}



const struct k_clock clock_aux = {

	.clock_getres		= aux_get_res,

	.clock_get_timespec	= aux_get_timespec,

	.clock_set		= aux_clock_set,

};



static __init void tk_aux_setup(void)