On some machine (nami), interrupt latency cause samples to appear
to be from the future and are pegged to the current time.
We would see samples with this pattern:
[t, t + ~5ms, t + ~10ms, t + ~10ms + 100us, t + ~10ms + 200us],
(current now) (current now)
(t is the last timestamp time)
Last 2 samples would be barely spread, causing applications to
complain.
We now spread the entire sequence. This is not great: in the example
the sensor was supposed to send samples every 5ms, it now appears to
send one every 2.5ms, but it is slightly closer to reality:
sampling time in the example above
At sensor level
1 2 3 4 5
+-----5ms-----+-----5ms-----+-----5ms-----+----5ms-----+---> t
Before, at host level
1 2 3 4 5
--interrupt delay------+-----5ms-----+-----5ms-----+-+-+---> t
Afer, at host level
1 2 3 4 5
--interrupt delay------+-2.5ms-+-2.5ms-+-2.5ms-+-2.5ms-+---> t
Signed-off-by: Gwendal Grignou <gwen...@chromium.org>
---
.../platform/chrome/cros_ec_sensorhub_ring.c | 94 +++++++------------
1 file changed, 33 insertions(+), 61 deletions(-)
diff --git a/drivers/platform/chrome/cros_ec_sensorhub_ring.c
b/drivers/platform/chrome/cros_ec_sensorhub_ring.c
index 1b9637655e63e..0b0bf93073c30 100644
--- a/drivers/platform/chrome/cros_ec_sensorhub_ring.c
+++ b/drivers/platform/chrome/cros_ec_sensorhub_ring.c
@@ -719,29 +719,22 @@ done_with_this_batch:
* cros_ec_sensor_ring_spread_add_legacy: Calculate proper timestamps then
* add to ringbuffer (legacy).
*
- * Note: This assumes we're running old firmware, where every sample's
timestamp
- * is after the sample. Run if tight_timestamps == false.
- *
- * If there is a sample with a proper timestamp
+ * Note: This assumes we're running old firmware, where timestamp
+ * is inserted after its sample(s)e. There can be several samples between
+ * timestamps, so several samples can have the same timestamp.
*
* timestamp | count
* -----------------
- * older_unprocess_out --> TS1 | 1
- * TS1 | 2
- * out --> TS1 | 3
- * next_out --> TS2 |
- *
- * We spread time for the samples [older_unprocess_out .. out]
- * between TS1 and TS2: [TS1+1/4, TS1+2/4, TS1+3/4, TS2].
+ * 1st sample --> TS1 | 1
+ * TS2 | 2
+ * TS2 | 3
+ * TS3 | 4
+ * last_out -->
*
- * If we reach the end of the samples, we compare with the
- * current timestamp:
*
- * older_unprocess_out --> TS1 | 1
- * TS1 | 2
- * out --> TS1 | 3
+ * We spread time for the samples using perod p = (current - TS1)/4.
+ * between TS1 and TS2: [TS1+p/4, TS1+2p/4, TS1+3p/4, current_timestamp].
*
- * We know have [TS1+1/3, TS1+2/3, current timestamp]
*/
static void
cros_ec_sensor_ring_spread_add_legacy(struct cros_ec_sensorhub *sensorhub,
@@ -754,58 +747,37 @@ cros_ec_sensor_ring_spread_add_legacy(struct
cros_ec_sensorhub *sensorhub,
int i;
for_each_set_bit(i, &sensor_mask, sensorhub->sensor_num) {
- s64 older_timestamp;
s64 timestamp;
- struct cros_ec_sensors_ring_sample *older_unprocess_out =
- sensorhub->ring;
- struct cros_ec_sensors_ring_sample *next_out;
- int count = 1;
-
- for (out = sensorhub->ring; out < last_out; out = next_out) {
- s64 time_period;
+ int count = 0;
+ s64 time_period;
- next_out = out + 1;
+ for (out = sensorhub->ring; out < last_out; out++) {
if (out->sensor_id != i)
continue;
/* Timestamp to start with */
- older_timestamp = out->timestamp;
-
- /* Find next sample. */
- while (next_out < last_out && next_out->sensor_id != i)
- next_out++;
+ timestamp = out->timestamp;
+ out++;
+ count = 1;
+ break;
+ }
+ for (; out < last_out; out++) {
+ /* Find last sample. */
+ if (out->sensor_id != i)
+ continue;
+ count++;
+ }
+ if (count == 0)
+ continue;
- if (next_out >= last_out) {
- timestamp = current_timestamp;
- } else {
- timestamp = next_out->timestamp;
- if (timestamp == older_timestamp) {
- count++;
- continue;
- }
- }
+ /* Spread uniformly between the first and last samples. */
+ time_period = div_s64(current_timestamp - timestamp, count);
- /*
- * The next sample has a new timestamp, spread the
- * unprocessed samples.
- */
- if (next_out < last_out)
- count++;
- time_period = div_s64(timestamp - older_timestamp,
- count);
-
- for (; older_unprocess_out <= out;
- older_unprocess_out++) {
- if (older_unprocess_out->sensor_id != i)
- continue;
- older_timestamp += time_period;
- older_unprocess_out->timestamp =
- older_timestamp;
- }
- count = 1;
- /* The next_out sample has a valid timestamp, skip. */
- next_out++;
- older_unprocess_out = next_out;
+ for (out = sensorhub->ring; out < last_out; out++) {
+ if (out->sensor_id != i)
+ continue;
+ timestamp += time_period;
+ out->timestamp = timestamp;
}
}
--
2.28.0.rc0.142.g3c755180ce-goog
