xref: /arm-trusted-firmware/include/lib/bakery_lock.h (revision 91f16700b400a8c0651d24a598fc48ee2997a0d7)

/*
 * Copyright (c) 2013-2018, Arm Limited and Contributors. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#ifndef BAKERY_LOCK_H
#define BAKERY_LOCK_H

#include <platform_def.h>

#define BAKERY_LOCK_MAX_CPUS		PLATFORM_CORE_COUNT

#ifndef __ASSEMBLER__
#include <cdefs.h>
#include <stdbool.h>
#include <stdint.h>

#include <lib/utils_def.h>

/*****************************************************************************
 * Internal helpers used by the bakery lock implementation.
 ****************************************************************************/

/* Convert a ticket to priority */
static inline unsigned int bakery_get_priority(unsigned int t, unsigned int pos)
{
	return (t << 8) | pos;
}

#define CHOOSING_TICKET		U(0x1)
#define CHOSEN_TICKET		U(0x0)

static inline bool bakery_is_choosing(unsigned int info)
{
	return (info & 1U) == CHOOSING_TICKET;
}

static inline unsigned int bakery_ticket_number(unsigned int info)
{
	return (info >> 1) & 0x7FFFU;
}

static inline uint16_t make_bakery_data(unsigned int choosing, unsigned int num)
{
	unsigned int val = (choosing & 0x1U) | (num << 1);

	return (uint16_t) val;
}

/*****************************************************************************
 * External bakery lock interface.
 ****************************************************************************/
#if USE_COHERENT_MEM
/*
 * Bakery locks are stored in coherent memory
 *
 * Each lock's data is contiguous and fully allocated by the compiler
 */

typedef struct bakery_lock {
	/*
	 * The lock_data is a bit-field of 2 members:
	 * Bit[0]       : choosing. This field is set when the CPU is
	 *                choosing its bakery number.
	 * Bits[1 - 15] : number. This is the bakery number allocated.
	 */
	volatile uint16_t lock_data[BAKERY_LOCK_MAX_CPUS];
} bakery_lock_t;

#else
/*
 * Bakery locks are stored in normal .bss memory
 *
 * Each lock's data is spread across multiple cache lines, one per CPU,
 * but multiple locks can share the same cache line.
 * The compiler will allocate enough memory for one CPU's bakery locks,
 * the remaining cache lines are allocated by the linker script
 */

typedef struct bakery_info {
	/*
	 * The lock_data is a bit-field of 2 members:
	 * Bit[0]       : choosing. This field is set when the CPU is
	 *                choosing its bakery number.
	 * Bits[1 - 15] : number. This is the bakery number allocated.
	 */
	volatile uint16_t lock_data;
} bakery_info_t;

typedef bakery_info_t bakery_lock_t;

#endif /* __USE_COHERENT_MEM__ */

static inline void bakery_lock_init(bakery_lock_t *bakery) {}
void bakery_lock_get(bakery_lock_t *bakery);
void bakery_lock_release(bakery_lock_t *bakery);

#define DEFINE_BAKERY_LOCK(_name) bakery_lock_t _name __section(".bakery_lock")

#define DECLARE_BAKERY_LOCK(_name) extern bakery_lock_t _name


#endif /* __ASSEMBLER__ */
#endif /* BAKERY_LOCK_H */