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authorMarti Bolivar <mbolivar@leaflabs.com>2012-04-09 15:14:01 -0400
committerMarti Bolivar <mbolivar@leaflabs.com>2012-04-11 16:56:56 -0400
commit42059788b4fff74fddfc7d391e82c316b6901211 (patch)
tree7fdf83114e7b50b1d04ea6d4206e69387a439019 /libmaple
parent68800148b998488f09fb36fde53970900c199c0a (diff)
downloadlibrambutan-42059788b4fff74fddfc7d391e82c316b6901211.tar.gz
librambutan-42059788b4fff74fddfc7d391e82c316b6901211.zip
libmaple/timer_private.h: Add more explanatory comments.
Hopefully these will be helpful when adding timer support for additional series in the future. Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>
Diffstat (limited to 'libmaple')
-rw-r--r--libmaple/timer_private.h43
1 files changed, 31 insertions, 12 deletions
diff --git a/libmaple/timer_private.h b/libmaple/timer_private.h
index f882f51..54e3ea1 100644
--- a/libmaple/timer_private.h
+++ b/libmaple/timer_private.h
@@ -34,21 +34,30 @@
#define _LIBMAPLE_TIMER_PRIVATE_H_
/*
- * Devices
+ * Helper macros for declaring timer_devs of various timer_types
*/
-/* Just like the corresponding DIER bits:
+/* The indexes of user handlers in a timer_dev.handlers are just like
+ * the corresponding DIER bits, as follows: */
+
+/* Advanced timers:
* [0] = Update handler;
* [1,2,3,4] = capture/compare 1,2,3,4 handlers, respectively;
* [5] = COM;
* [6] = TRG;
* [7] = BRK. */
#define NR_ADV_HANDLERS 8
-/* Update, capture/compare 1,2,3,4; <junk>; trigger. */
+/* General purpose timers:
+ * [0] = update;
+ * [1,2,3,4] = capture/compare 1,2,3,4;
+ * [5] = <junk>;
+ * [6] = trigger. */
#define NR_GEN_HANDLERS 7
-/* Update only. */
+/* Basic timers:
+ * [0] = update. */
#define NR_BAS_HANDLERS 1
+/* For declaring advanced timers. */
#define DECLARE_ADVANCED_TIMER(name, num) \
timer_dev name = { \
.regs = { .adv = TIMER##num##_BASE }, \
@@ -57,6 +66,7 @@
.handlers = { [NR_ADV_HANDLERS - 1] = 0 }, \
}
+/* For declaring full-featured general purpose timers. */
#define DECLARE_GENERAL_TIMER(name, num) \
timer_dev name = { \
.regs = { .gen = TIMER##num##_BASE }, \
@@ -65,6 +75,7 @@
.handlers = { [NR_GEN_HANDLERS - 1] = 0 }, \
}
+/* For declaring basic timers (e.g. TIM6 and TIM7). */
#define DECLARE_BASIC_TIMER(name, num) \
timer_dev name = { \
.regs = { .bas = TIMER##num##_BASE }, \
@@ -75,13 +86,21 @@
/*
* IRQ handlers
- */
-
-/* Note: the following dispatch routines make use of the fact that
- * DIER interrupt enable bits and SR interrupt flags have common bit
- * positions. Thus, ANDing DIER and SR lets us check if an interrupt
- * is enabled and if it has occurred simultaneously.
- */
+ *
+ * These decode TIMx_DIER and TIMx_SR, then dispatch to the user-level
+ * IRQ handlers. They also clean up TIMx_SR afterwards, so the user
+ * doesn't have to deal with register details.
+ *
+ * Notes:
+ *
+ * - These dispatch routines make use of the fact that DIER interrupt
+ * enable bits and SR interrupt flags have common bit positions.
+ * Thus, ANDing DIER and SR lets us check if an interrupt is enabled
+ * and if it has occurred simultaneously.
+ *
+ * - We force these routines to inline to avoid call overhead, but
+ * there aren't any measurements to prove that this is actually a
+ * good idea. Profile-directed optimizations are definitely wanted. */
/* A special-case dispatch routine for single-interrupt NVIC lines.
* This function assumes that the interrupt corresponding to `iid' has
@@ -97,7 +116,7 @@ static __always_inline void dispatch_single_irq(timer_dev *dev,
}
}
-/* For dispatch routines which service multiple interrupts. */
+/* Helper macro for dispatch routines which service multiple interrupts. */
#define handle_irq(dier_sr, irq_mask, handlers, iid, handled_irq) do { \
if ((dier_sr) & (irq_mask)) { \
void (*__handler)(void) = (handlers)[iid]; \