// SPDX-License-Identifier: GPL-2.0/* * Emulate a local clock event device via a pseudo clock device. */#include <linux/cpu.h>#include <linux/err.h>#include <linux/hrtimer.h>#include <linux/interrupt.h>#include <linux/percpu.h>#include <linux/profile.h>#include <linux/clockchips.h>#include <linux/sched.h>#include <linux/smp.h>#include <linux/module.h> #include "tick-internal.h" static struct hrtimer bctimer; static int bc_shutdown(struct clock_event_device *evt){	/*	 * Note, we cannot cancel the timer here as we might	 * run into the following live lock scenario:	 *	 * cpu 0		cpu1	 * lock(broadcast_lock);	 *			hrtimer_interrupt()	 *			bc_handler()	 *			   tick_handle_oneshot_broadcast();	 *			    lock(broadcast_lock);	 * hrtimer_cancel()	 *  wait_for_callback()	 */	hrtimer_try_to_cancel(&bctimer);	return 0;} /* * This is called from the guts of the broadcast code when the cpu * which is about to enter idle has the earliest broadcast timer event. */static int bc_set_next(ktime_t expires, struct clock_event_device *bc){	/*	 * This is called either from enter/exit idle code or from the	 * broadcast handler. In all cases tick_broadcast_lock is held.	 *	 * hrtimer_cancel() cannot be called here neither from the	 * broadcast handler nor from the enter/exit idle code. The idle	 * code can run into the problem described in bc_shutdown() and the	 * broadcast handler cannot wait for itself to complete for obvious	 * reasons.	 *	 * Each caller tries to arm the hrtimer on its own CPU, but if the	 * hrtimer callback function is currently running, then	 * hrtimer_start() cannot move it and the timer stays on the CPU on	 * which it is assigned at the moment.	 */	hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED_HARD);	/*	 * The core tick broadcast mode expects bc->bound_on to be set	 * correctly to prevent a CPU which has the broadcast hrtimer	 * armed from going deep idle.	 *	 * As tick_broadcast_lock is held, nothing can change the cpu	 * base which was just established in hrtimer_start() above. So	 * the below access is safe even without holding the hrtimer	 * base lock.	 */	bc->bound_on = bctimer.base->cpu_base->cpu; 	return 0;} static struct clock_event_device ce_broadcast_hrtimer = {	.name			= "bc_hrtimer",	.set_state_shutdown	= bc_shutdown,	.set_next_ktime		= bc_set_next,	.features		= CLOCK_EVT_FEAT_ONESHOT |				  CLOCK_EVT_FEAT_HRTIMER,	.rating			= 0,	.bound_on		= -1,	.min_delta_ns		= 1,	.max_delta_ns		= KTIME_MAX,	.min_delta_ticks	= 1,	.max_delta_ticks	= ULONG_MAX,	.mult			= 1,	.shift			= 0,	.cpumask		= cpu_possible_mask,}; static enum hrtimer_restart bc_handler(struct hrtimer *t){	ce_broadcast_hrtimer.event_handler(&ce_broadcast_hrtimer); 	return HRTIMER_NORESTART;} void tick_setup_hrtimer_broadcast(void){	hrtimer_setup(&bctimer, bc_handler, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);	clockevents_register_device(&ce_broadcast_hrtimer);}