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authorOhad Ben-Cohen <ohad@wizery.com>2011-09-05 16:15:06 -0400
committerOhad Ben-Cohen <ohad@wizery.com>2011-09-21 12:45:32 -0400
commitc3c1250e93a7ab1327a9fc49d2a22405672f4204 (patch)
tree2dc99df2ab4657de87a66da7d0a047a95ff27711 /include/linux/hwspinlock.h
parentc97f6dd0fe21dfd658c59c144a1b7fd5d8db04ac (diff)
hwspinlock/core/omap: fix id issues on multiple hwspinlock devices
hwspinlock devices provide system-wide hardware locks that are used by remote processors that have no other way to achieve synchronization. To achieve that, each physical lock must have a system-wide id number that is agreed upon, otherwise remote processors can't possibly assume they're using the same hardware lock. Usually boards have a single hwspinlock device, which provides several hwspinlocks, and in this case, they can be trivially numbered 0 to (num-of-locks - 1). In case boards have several hwspinlocks devices, a different base id should be used for each hwspinlock device (they can't all use 0 as a starting id!). While this is certainly not common, it's just plain wrong to just silently use 0 as a base id whenever the hwspinlock driver is probed. This patch provides a hwspinlock_pdata structure, that boards can use to set a different base id for each of the hwspinlock devices they may have, and demonstrates how to use it with the omap hwspinlock driver. While we're at it, make sure the hwspinlock core prints an explicit error message in case an hwspinlock is registered with an id number that already exists; this will help users catch such base id issues. Reported-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com> Acked-by: Tony Lindgren <tony@atomide.com>
Diffstat (limited to 'include/linux/hwspinlock.h')
-rw-r--r--include/linux/hwspinlock.h28
1 files changed, 28 insertions, 0 deletions
diff --git a/include/linux/hwspinlock.h b/include/linux/hwspinlock.h
index 8390efc457eb..f85cef5452f2 100644
--- a/include/linux/hwspinlock.h
+++ b/include/linux/hwspinlock.h
@@ -27,6 +27,34 @@
27 27
28struct hwspinlock; 28struct hwspinlock;
29 29
30/**
31 * struct hwspinlock_pdata - platform data for hwspinlock drivers
32 * @base_id: base id for this hwspinlock device
33 *
34 * hwspinlock devices provide system-wide hardware locks that are used
35 * by remote processors that have no other way to achieve synchronization.
36 *
37 * To achieve that, each physical lock must have a system-wide id number
38 * that is agreed upon, otherwise remote processors can't possibly assume
39 * they're using the same hardware lock.
40 *
41 * Usually boards have a single hwspinlock device, which provides several
42 * hwspinlocks, and in this case, they can be trivially numbered 0 to
43 * (num-of-locks - 1).
44 *
45 * In case boards have several hwspinlocks devices, a different base id
46 * should be used for each hwspinlock device (they can't all use 0 as
47 * a starting id!).
48 *
49 * This platform data structure should be used to provide the base id
50 * for each device (which is trivially 0 when only a single hwspinlock
51 * device exists). It can be shared between different platforms, hence
52 * its location.
53 */
54struct hwspinlock_pdata {
55 int base_id;
56};
57
30#if defined(CONFIG_HWSPINLOCK) || defined(CONFIG_HWSPINLOCK_MODULE) 58#if defined(CONFIG_HWSPINLOCK) || defined(CONFIG_HWSPINLOCK_MODULE)
31 59
32int hwspin_lock_register(struct hwspinlock *lock); 60int hwspin_lock_register(struct hwspinlock *lock);