From cd920a0e5321166ef8b1d6afc3d63fc5de998a93 Mon Sep 17 00:00:00 2001
From: Keith Packard <keithp@keithp.com>
Date: Mon, 25 Feb 2019 16:42:25 -0700
Subject: altos: add ao_time_ns API

This provides nano-second resolution times by reading the systick
value (which runs at 250ns ticks on stm).

Signed-off-by: Keith Packard <keithp@keithp.com>
---
 src/stmf0/ao_timer.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

(limited to 'src/stmf0')

diff --git a/src/stmf0/ao_timer.c b/src/stmf0/ao_timer.c
index 1def5f69..58e52995 100644
--- a/src/stmf0/ao_timer.c
+++ b/src/stmf0/ao_timer.c
@@ -35,6 +35,22 @@ ao_time(void)
 	return ao_tick_count;
 }
 
+uint64_t
+ao_time_ns(void)
+{
+	AO_TICK_TYPE	before, after;
+	uint32_t	cvr;
+
+	do {
+		before = ao_tick_count;
+		cvr = stm_systick.cvr;
+		after = ao_tick_count;
+	} while (before != after);
+
+	return (uint64_t) after * (1000000000ULL / AO_HERTZ) +
+		(uint64_t) cvr * (1000000000ULL / AO_SYSTICK);
+}
+
 #if AO_DATA_ALL
 volatile uint8_t	ao_data_interval = 1;
 volatile uint8_t	ao_data_count;
-- 
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