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authorOhad Ben-Cohen <ohad@wizery.com>2011-09-05 23:15:06 +0300
committerOhad Ben-Cohen <ohad@wizery.com>2011-09-21 19:45:32 +0300
commitc3c1250e93a7ab1327a9fc49d2a22405672f4204 (patch)
tree2dc99df2ab4657de87a66da7d0a047a95ff27711 /include/linux/hwspinlock.h
parentc97f6dd0fe21dfd658c59c144a1b7fd5d8db04ac (diff)
downloadop-kernel-dev-c3c1250e93a7ab1327a9fc49d2a22405672f4204.zip
op-kernel-dev-c3c1250e93a7ab1327a9fc49d2a22405672f4204.tar.gz
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 8390efc..f85cef5 100644
--- a/include/linux/hwspinlock.h
+++ b/include/linux/hwspinlock.h
@@ -27,6 +27,34 @@
struct hwspinlock;
+/**
+ * struct hwspinlock_pdata - platform data for hwspinlock drivers
+ * @base_id: base id for this hwspinlock device
+ *
+ * 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!).
+ *
+ * This platform data structure should be used to provide the base id
+ * for each device (which is trivially 0 when only a single hwspinlock
+ * device exists). It can be shared between different platforms, hence
+ * its location.
+ */
+struct hwspinlock_pdata {
+ int base_id;
+};
+
#if defined(CONFIG_HWSPINLOCK) || defined(CONFIG_HWSPINLOCK_MODULE)
int hwspin_lock_register(struct hwspinlock *lock);
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