[PATCH v4 10/17] platform: chrome: sensorhub: Add code to spread timestmap

Gwendal Grignou
2019-11-05T22:27:57Z

EC FIFO can send sensor events in batch. Spread them based on
previous (TSa) and currnet timestamp (TSb)

EC FIFO iio events
+-----------+
| TSa |
+-----------+ +---------------------------------------+
| event 1 | | event 1 | TSb - (TSb - TSa)/n * (n-1) |
+-----------+ +---------------------------------------+
| event 2 | | event 2 | TSb - (TSb - TSa)/n * (n-2) |
+-----------+ +---------------------------------------+
| ... | ------> | .... | |
+-----------+ +---------------------------------------+
| event n-1 | | event 2 | TSb - (TSb - TSa)/n |
+-----------+ +---------------------------------------+
| event n | | event 2 | TSb |
+-----------+ +---------------------------------------+
| TSb |
+-----------+

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
---
Changes in v4:
- Check patch with --strict option
Alignement
No changes in v3.
Changes in v2:
- Use CROS_EC_SENSOR_LAST_TS instead of LAST_TS to avoid name colisions.

.../platform/chrome/cros_ec_sensorhub_ring.c | 98 ++++++++++++++++++-
1 file changed, 95 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_sensorhub_ring.c b/drivers/platform/chrome/cros_ec_sensorhub_ring.c
index f091f2a4ccfe..b22a71406742 100644
--- a/drivers/platform/chrome/cros_ec_sensorhub_ring.c
+++ b/drivers/platform/chrome/cros_ec_sensorhub_ring.c
@@ -187,6 +187,96 @@ static bool cros_ec_ring_process_event(struct cros_ec_sensorhub *sensorhub,
return true;
}

+/*
+ * cros_ec_ring_spread_add: Calculate proper timestamps then
+ * add to ringbuffer (legacy).
+ *
+ * If there is a sample with a proper 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].
+ *
+ * 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 know have [TS1+1/3, TS1+2/3, current timestamp]
+ */
+static void cros_ec_ring_spread_add(struct cros_ec_sensorhub *sensorhub,
+ unsigned long sensor_mask,
+ s64 current_timestamp,
+ struct cros_ec_sensors_ring_sample *last_out)
+{
+ struct cros_ec_sensors_ring_sample *out;
+ int i;
+
+ for_each_set_bit(i, &sensor_mask, BITS_PER_LONG) {
+ 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;
+
+ next_out = out + 1;
+ 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++;
+
+ if (next_out >= last_out) {
+ timestamp = current_timestamp;
+ } else {
+ timestamp = next_out->timestamp;
+ if (timestamp == older_timestamp) {
+ count++;
+ continue;
+ }
+ }
+
+ /*
+ * 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;
+ }
+ }
+
+ /* push the event into the kfifo */
+ for (out = sensorhub->ring; out < last_out; out++)
+ cros_sensorhub_send_sample(sensorhub, out);
+}
+
/*
* cros_ec_sensorhub_ring_handler - the trigger handler function
*
@@ -322,9 +412,11 @@ static void cros_ec_sensorhub_ring_handler(struct cros_ec_sensorhub *sensorhub)
}
}

- /* push the event into the kfifo */
- for (out = sensorhub->ring; out < last_out; out++)
- cros_sensorhub_send_sample(sensorhub, out);
+ /*
+ * Spread samples in case of batching, then add them to the ringbuffer.
+ */
+ cros_ec_ring_spread_add(sensorhub, sensor_mask,
+ current_timestamp, last_out);

ring_handler_end:
sensorhub->fifo_timestamp[CROS_EC_SENSOR_LAST_TS] = current_timestamp;
--
2.24.0.rc1.363.gb1bccd3e3d-goog