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+/*
+ * Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <arch_helpers.h>
+#include <assert.h>
+#include <bakery_lock.h>
+#include <cpu_data.h>
+#include <platform.h>
+#include <string.h>
+
+/*
+ * Functions in this file implement Bakery Algorithm for mutual exclusion with the
+ * bakery lock data structures in cacheable and Normal memory.
+ *
+ * ARM architecture offers a family of exclusive access instructions to
+ * efficiently implement mutual exclusion with hardware support. However, as
+ * well as depending on external hardware, these instructions have defined
+ * behavior only on certain memory types (cacheable and Normal memory in
+ * particular; see ARMv8 Architecture Reference Manual section B2.10). Use cases
+ * in trusted firmware are such that mutual exclusion implementation cannot
+ * expect that accesses to the lock have the specific type required by the
+ * architecture for these primitives to function (for example, not all
+ * contenders may have address translation enabled).
+ *
+ * This implementation does not use mutual exclusion primitives. It expects
+ * memory regions where the locks reside to be cacheable and Normal.
+ *
+ * Note that the ARM architecture guarantees single-copy atomicity for aligned
+ * accesses regardless of status of address translation.
+ */
+
+/* Convert a ticket to priority */
+#define PRIORITY(t, pos) (((t) << 8) | (pos))
+
+#define CHOOSING_TICKET 0x1
+#define CHOOSING_DONE 0x0
+
+#define bakery_is_choosing(info) (info & 0x1)
+#define bakery_ticket_number(info) ((info >> 1) & 0x7FFF)
+#define make_bakery_data(choosing, number) \
+ (((choosing & 0x1) | (number << 1)) & 0xFFFF)
+
+/* This macro assumes that the bakery_info array is located at the offset specified */
+#define get_my_bakery_info(offset, id) \
+ (((bakery_info_t *) (((uint8_t *)_cpu_data()) + offset)) + id)
+
+#define get_bakery_info_by_index(offset, id, ix) \
+ (((bakery_info_t *) (((uint8_t *)_cpu_data_by_index(ix)) + offset)) + id)
+
+#define write_cache_op(addr, cached) \
+ do { \
+ (cached ? dccvac((uint64_t)addr) :\
+ dcivac((uint64_t)addr));\
+ dsbish();\
+ } while (0)
+
+#define read_cache_op(addr, cached) if (cached) \
+ dccivac((uint64_t)addr)
+
+static unsigned int bakery_get_ticket(int id, unsigned int offset,
+ unsigned int me, int is_cached)
+{
+ unsigned int my_ticket, their_ticket;
+ unsigned int they;
+ bakery_info_t *my_bakery_info, *their_bakery_info;
+
+ /*
+ * Obtain a reference to the bakery information for this cpu and ensure
+ * it is not NULL.
+ */
+ my_bakery_info = get_my_bakery_info(offset, id);
+ assert(my_bakery_info);
+
+ /*
+ * Tell other contenders that we are through the bakery doorway i.e.
+ * going to allocate a ticket for this cpu.
+ */
+ my_ticket = 0;
+ my_bakery_info->lock_data = make_bakery_data(CHOOSING_TICKET, my_ticket);
+
+ write_cache_op(my_bakery_info, is_cached);
+
+ /*
+ * Iterate through the bakery information of each contender to allocate
+ * the highest ticket number for this cpu.
+ */
+ for (they = 0; they < BAKERY_LOCK_MAX_CPUS; they++) {
+ if (me == they)
+ continue;
+
+ /*
+ * Get a reference to the other contender's bakery info and
+ * ensure that a stale copy is not read.
+ */
+ their_bakery_info = get_bakery_info_by_index(offset, id, they);
+ assert(their_bakery_info);
+
+ read_cache_op(their_bakery_info, is_cached);
+
+ /*
+ * Update this cpu's ticket number if a higher ticket number is
+ * seen
+ */
+ their_ticket = bakery_ticket_number(their_bakery_info->lock_data);
+ if (their_ticket > my_ticket)
+ my_ticket = their_ticket;
+ }
+
+ /*
+ * Compute ticket; then signal to other contenders waiting for us to
+ * finish calculating our ticket value that we're done
+ */
+ ++my_ticket;
+ my_bakery_info->lock_data = make_bakery_data(CHOOSING_DONE, my_ticket);
+
+ write_cache_op(my_bakery_info, is_cached);
+
+ return my_ticket;
+}
+
+void bakery_lock_get(unsigned int id, unsigned int offset)
+{
+ unsigned int they, me, is_cached;
+ unsigned int my_ticket, my_prio, their_ticket;
+ bakery_info_t *their_bakery_info;
+ uint16_t their_bakery_data;
+
+ me = platform_get_core_pos(read_mpidr_el1());
+
+ is_cached = read_sctlr_el3() & SCTLR_C_BIT;
+
+ /* Get a ticket */
+ my_ticket = bakery_get_ticket(id, offset, me, is_cached);
+
+ /*
+ * Now that we got our ticket, compute our priority value, then compare
+ * with that of others, and proceed to acquire the lock
+ */
+ my_prio = PRIORITY(my_ticket, me);
+ for (they = 0; they < BAKERY_LOCK_MAX_CPUS; they++) {
+ if (me == they)
+ continue;
+
+ /*
+ * Get a reference to the other contender's bakery info and
+ * ensure that a stale copy is not read.
+ */
+ their_bakery_info = get_bakery_info_by_index(offset, id, they);
+ assert(their_bakery_info);
+ read_cache_op(their_bakery_info, is_cached);
+
+ their_bakery_data = their_bakery_info->lock_data;
+
+ /* Wait for the contender to get their ticket */
+ while (bakery_is_choosing(their_bakery_data)) {
+ read_cache_op(their_bakery_info, is_cached);
+ their_bakery_data = their_bakery_info->lock_data;
+ }
+
+ /*
+ * If the other party is a contender, they'll have non-zero
+ * (valid) ticket value. If they do, compare priorities
+ */
+ their_ticket = bakery_ticket_number(their_bakery_data);
+ if (their_ticket && (PRIORITY(their_ticket, they) < my_prio)) {
+ /*
+ * They have higher priority (lower value). Wait for
+ * their ticket value to change (either release the lock
+ * to have it dropped to 0; or drop and probably content
+ * again for the same lock to have an even higher value)
+ */
+ do {
+ wfe();
+ read_cache_op(their_bakery_info, is_cached);
+ } while (their_ticket
+ == bakery_ticket_number(their_bakery_info->lock_data));
+ }
+ }
+}
+
+void bakery_lock_release(unsigned int id, unsigned int offset)
+{
+ bakery_info_t *my_bakery_info;
+ unsigned int is_cached = read_sctlr_el3() & SCTLR_C_BIT;
+
+ my_bakery_info = get_my_bakery_info(offset, id);
+ my_bakery_info->lock_data = 0;
+ write_cache_op(my_bakery_info, is_cached);
+ sev();
+}