We are currently synchronizing every time the data timestamp with
the IT timestamp, leading to system jitter jamming timestamps.
To fix that and keep it simple, let's just synchronize when the
delta is bigger than the acceptable jitter, and keep
synchronization at the jitter value.
The result is much stable timestamps reflecting better the real
physical value. Example @50Hz delta timestamp,
* before: 20.123ms, 19.721ms, 20.023ms, 20.353ms, 19.821ms, ...
* after: 20.173ms, 20.173ms, 20.173ms, 20.40ms, 20.173ms, ...
Refactorize code and delete the unnecessary handling of multiple
FIFO data.
Signed-off-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
Link: https://lore.kernel.org/r/20230522093210.817212-1-inv.git-commit@tdk.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Add a timestamping mechanism for buffer that provides accurate
event timestamps when using watermark. This mechanism estimates
device internal clock by comparing FIFO interrupts delta time and
device elapsed time computed by parsing FIFO data.
Take interrupt timestamp in hard irq handler and add IIO device
specific timestamp structures in device private allocation.
Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
