ptimer: Add TRIGGER_ONLY_ON_DECREMENT policy option

The CMSDK timer behaviour is that an interrupt is triggered when the
counter counts down from 1 to 0; however one is not triggered if the
counter is manually set to 0 by a guest write to the counter register.
Currently ptimer can't handle this; add a policy option to allow
a ptimer user to request this behaviour.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Message-id: 20180703171044.9503-2-peter.maydell@linaro.org

1 files changed, 9 insertions, 0 deletions

diff --git a/include/hw/ptimer.h b/include/hw/ptimer.h
index fc4ef5cc1d..0731d9aef1 100644
--- a/include/hw/ptimer.h
+++ b/include/hw/ptimer.h
@@ -69,6 +69,15 @@
  * not the one less.  */
 #define PTIMER_POLICY_NO_COUNTER_ROUND_DOWN (1 << 4)
 
+/*
+ * Starting to run with a zero counter, or setting the counter to "0" via
+ * ptimer_set_count() or ptimer_set_limit() will not trigger the timer
+ * (though it will cause a reload). Only a counter decrement to "0"
+ * will cause a trigger. Not compatible with NO_IMMEDIATE_TRIGGER;
+ * ptimer_init() will assert() that you don't set both.
+ */
+#define PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT (1 << 5)
+
 /* ptimer.c */
 typedef struct ptimer_state ptimer_state;
 typedef void (*ptimer_cb)(void *opaque);