[PATCH v7 03/12] platform: chrome: sensorhub: Add code to spread timestmap

From: Gwendal Grignou
Date: Fri Mar 27 2020 - 18:34:54 EST

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 |
+-----------+

Acked-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Acked-by: Lee Jones <lee.jones@xxxxxxxxxx>
Signed-off-by: Gwendal Grignou <gwendal@xxxxxxxxxxxx>
---
Changes in v7:
- Use the number of sensors present to limit the scan of sensr mask.
fifo_info is now a separate structure.
Changes in v6:
Comment fixes
Changes in v5:
Added ack.
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 | 117 ++++++++++++++++--
1 file changed, 109 insertions(+), 8 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_sensorhub_ring.c b/drivers/platform/chrome/cros_ec_sensorhub_ring.c
index da73757529ca5..443db8277d2b9 100644
--- a/drivers/platform/chrome/cros_ec_sensorhub_ring.c
+++ b/drivers/platform/chrome/cros_ec_sensorhub_ring.c
@@ -190,6 +190,101 @@ cros_ec_sensor_ring_process_event(struct cros_ec_sensorhub *sensorhub,
return true;
}

+/*
+ * cros_ec_sensor_ring_spread_add: Calculate proper timestamps then add to
+ * ringbuffer.
+ *
+ * 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_sensor_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, 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;
+
+ 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
*
@@ -204,6 +299,7 @@ static void cros_ec_sensorhub_ring_handler(struct cros_ec_sensorhub *sensorhub)
struct cros_ec_dev *ec = sensorhub->ec;
ktime_t fifo_timestamp, current_timestamp;
int i, j, number_data, ret;
+ unsigned long sensor_mask = 0;
struct ec_response_motion_sensor_data *in;
struct cros_ec_sensors_ring_sample *out, *last_out;

@@ -289,8 +385,10 @@ static void cros_ec_sensorhub_ring_handler(struct cros_ec_sensorhub *sensorhub)
sensorhub, fifo_info,
fifo_timestamp,
&current_timestamp,
- in, out))
+ in, out)) {
+ sensor_mask |= BIT(in->sensor_num);
out++;
+ }
}
}
mutex_unlock(&sensorhub->cmd_lock);
@@ -301,10 +399,10 @@ static void cros_ec_sensorhub_ring_handler(struct cros_ec_sensorhub *sensorhub)
goto ring_handler_end;

/*
- * Check if current_timestamp is ahead of the last sample.
- * Normally, the EC appends a timestamp after the last sample, but if
- * the AP is slow to respond to the IRQ, the EC may have added new
- * samples. Use the FIFO info timestamp as last timestamp then.
+ * Check if current_timestamp is ahead of the last sample. Normally,
+ * the EC appends a timestamp after the last sample, but if the AP
+ * is slow to respond to the IRQ, the EC may have added new samples.
+ * Use the FIFO info timestamp as last timestamp then.
*/
if ((last_out - 1)->timestamp == current_timestamp)
current_timestamp = fifo_timestamp;
@@ -319,9 +417,12 @@ static void cros_ec_sensorhub_ring_handler(struct cros_ec_sensorhub *sensorhub)
fifo_info->total_lost);
}

- /* Push the event into the FIFO. */
- 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_sensor_ring_spread_add(sensorhub, sensor_mask,
+ current_timestamp, last_out);

ring_handler_end:
sensorhub->fifo_timestamp[CROS_EC_SENSOR_LAST_TS] = current_timestamp;
--
2.26.0.rc2.310.g2932bb562d-goog