Optimize the bakery lock structure for coherent memory

This patch optimizes the data structure used with the bakery lock
implementation for coherent memory to save memory and minimize memory
accesses. These optimizations were already part of the bakery lock
implementation for normal memory and this patch now implements
it for the coherent memory implementation as well. Also
included in the patch is a cleanup to use the do-while loop while
waiting for other contenders to finish choosing their tickets.

Change-Id: Iedb305473133dc8f12126726d8329b67888b70f1

2 files changed, 16 insertions, 32 deletions

diff --git a/lib/locks/bakery/bakery_lock_coherent.c b/lib/locks/bakery/bakery_lock_coherent.c
index 5d538ce2..02d31d64 100644
--- a/lib/locks/bakery/bakery_lock_coherent.c
+++ b/lib/locks/bakery/bakery_lock_coherent.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2014, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2015, 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:
@@ -63,10 +63,6 @@
 	assert(entry < BAKERY_LOCK_MAX_CPUS);		\
 } while (0)
 
-/* Convert a ticket to priority */
-#define PRIORITY(t, pos)	(((t) << 8) | (pos))
-
-
 /* Initialize Bakery Lock to reset ownership and all ticket values */
 void bakery_lock_init(bakery_lock_t *bakery)
 {
@@ -95,9 +91,9 @@ static unsigned int bakery_get_ticket(bakery_lock_t *bakery, unsigned int me)
 	 * value, not the ticket value alone.
 	 */
 	my_ticket = 0;
-	bakery->entering[me] = 1;
+	bakery->lock_data[me] = make_bakery_data(CHOOSING_TICKET, my_ticket);
 	for (they = 0; they < BAKERY_LOCK_MAX_CPUS; they++) {
-		their_ticket = bakery->number[they];
+		their_ticket = bakery_ticket_number(bakery->lock_data[they]);
 		if (their_ticket > my_ticket)
 			my_ticket = their_ticket;
 	}
@@ -107,8 +103,7 @@ static unsigned int bakery_get_ticket(bakery_lock_t *bakery, unsigned int me)
 	 * finish calculating our ticket value that we're done
 	 */
 	++my_ticket;
-	bakery->number[me] = my_ticket;
-	bakery->entering[me] = 0;
+	bakery->lock_data[me] = make_bakery_data(CHOSEN_TICKET, my_ticket);
 
 	return my_ticket;
 }
@@ -129,6 +124,7 @@ void bakery_lock_get(bakery_lock_t *bakery)
 {
 	unsigned int they, me;
 	unsigned int my_ticket, my_prio, their_ticket;
+	unsigned int their_bakery_data;
 
 	me = platform_get_core_pos(read_mpidr_el1());
 
@@ -150,14 +146,15 @@ void bakery_lock_get(bakery_lock_t *bakery)
 			continue;
 
 		/* Wait for the contender to get their ticket */
-		while (bakery->entering[they])
-			;
+		do {
+			their_bakery_data = bakery->lock_data[they];
+		} while (bakery_is_choosing(their_bakery_data));
 
 		/*
 		 * If the other party is a contender, they'll have non-zero
 		 * (valid) ticket value. If they do, compare priorities
 		 */
-		their_ticket = bakery->number[they];
+		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
@@ -167,7 +164,8 @@ void bakery_lock_get(bakery_lock_t *bakery)
 			 */
 			do {
 				wfe();
-			} while (their_ticket == bakery->number[they]);
+			} while (their_ticket ==
+				bakery_ticket_number(bakery->lock_data[they]));
 		}
 	}
 
@@ -189,7 +187,7 @@ void bakery_lock_release(bakery_lock_t *bakery)
 	 * waiting contenders
 	 */
 	bakery->owner = NO_OWNER;
-	bakery->number[me] = 0;
+	bakery->lock_data[me] = 0;
 	dsb();
 	sev();
 }
diff --git a/lib/locks/bakery/bakery_lock_normal.c b/lib/locks/bakery/bakery_lock_normal.c
index a325fd4f..4503ae09 100644
--- a/lib/locks/bakery/bakery_lock_normal.c
+++ b/lib/locks/bakery/bakery_lock_normal.c
@@ -56,17 +56,6 @@
  * 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)
@@ -138,7 +127,7 @@ static unsigned int bakery_get_ticket(int id, unsigned int offset,
 	 * finish calculating our ticket value that we're done
 	 */
 	++my_ticket;
-	my_bakery_info->lock_data = make_bakery_data(CHOOSING_DONE, my_ticket);
+	my_bakery_info->lock_data = make_bakery_data(CHOSEN_TICKET, my_ticket);
 
 	write_cache_op(my_bakery_info, is_cached);
 
@@ -150,7 +139,7 @@ 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;
+	unsigned int their_bakery_data;
 
 	me = platform_get_core_pos(read_mpidr_el1());
 
@@ -174,15 +163,12 @@ void bakery_lock_get(unsigned int id, unsigned int offset)
 		 */
 		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)) {
+		do {
 			read_cache_op(their_bakery_info, is_cached);
 			their_bakery_data = their_bakery_info->lock_data;
-		}
+		} while (bakery_is_choosing(their_bakery_data));
 
 		/*
 		 * If the other party is a contender, they'll have non-zero