[PATCH v5 00/10] iio: accel: adxl345: add FIFO operating with IRQ triggered watermark events

Lothar Rubusch
2024-12-05T17:13:51Z

The adxl345 sensor offers several features. Most of them are based on
using the hardware FIFO and reacting on events coming in on an interrupt
line. Add access to configure and read out the FIFO, handling of interrupts
and configuration and application of the watermark feature on that FIFO.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
---
Although I tried to implement most of the requested changes, now the code
is simplified and clearer, I still encounter some issues.

1) Unsure if my way reading out the FIFO elements with a regmap_noinc_read()
is supposed to be like that. TBH, isn't there a better way, say, to
configure the channel correctly and this is handled by the iio API
internally? As I understood from v2 there might be a way using
available data, also in iio_info I see now as buffer attributes an
available data field. Where can I find information how to use it or
did I get this wrong?

2) Overrun handling: I'm trying to reset the FIFO and registers. Unsure,
if this is the correct dealing here.

3) I can see the IRQs coming in, and with a `watch -n 0.1 iio_info` I can
see the correct fields changing. I tried the follwoing down below,
but the iio_readdev shows me the following result. I don't quite
understand if I still have an issue here, or if this is a calibration
thing?

# iio_info
Library version: 0.23 (git tag: v0.23)
Compiled with backends: local xml ip usb
IIO context created with local backend.
Backend version: 0.23 (git tag: v0.23)
Backend description string: Linux dut1138 6.6.21-lothar02 #3 SMP PREEMPT Wed Nov 6 21:21:14 UTC 2024 aarch64
IIO context has 2 attributes:
local,kernel: 6.6.21-lothar02
uri: local:
IIO context has 1 devices:
iio:device0: adxl345 (buffer capable)
3 channels found:
accel_x: (input, index: 0, format: le:s13/16>>0)
4 channel-specific attributes found:
attr 0: calibbias value: 0
attr 1: raw value: -14 <--- CHANGES
attr 2: sampling_frequency value: 100.000000000
attr 3: scale value: 0.038300
accel_y: (input, index: 1, format: le:s13/16>>0)
4 channel-specific attributes found:
attr 0: calibbias value: 0
attr 1: raw value: 6 <--- CHANGES
attr 2: sampling_frequency value: 100.000000000
attr 3: scale value: 0.038300
accel_z: (input, index: 2, format: le:s13/16>>0)
4 channel-specific attributes found:
attr 0: calibbias value: 0
attr 1: raw value: 247 <--- CHANGES
attr 2: sampling_frequency value: 100.000000000
attr 3: scale value: 0.038300
2 device-specific attributes found:
attr 0: sampling_frequency_available value: 0.09765625 0.1953125 0.390625 0.78125 1.5625 3.125 6.25 12.5 25 50 100 200 400 800 1600 3200
attr 1: waiting_for_supplier value: 0
3 buffer-specific attributes found:
attr 0: data_available value: 13
attr 1: direction value: in
attr 2: watermark value: 15
No trigger on this device

Above I marked what keeps changing with "CHANGES", that's what I expect. Then with readdev
I obtain the following result.

# iio_attr -c adxl345
dev 'adxl345', channel 'accel_x' (input, index: 0, format: le:s13/16>>0), found 4 channel-specific attributes
dev 'adxl345', channel 'accel_y' (input, index: 1, format: le:s13/16>>0), found 4 channel-specific attributes
dev 'adxl345', channel 'accel_z' (input, index: 2, format: le:s13/16>>0), found 4 channel-specific attributes
# echo 1 > ./scan_elements/in_accel_x_en
# echo 1 > ./scan_elements/in_accel_y_en
# echo 1 > ./scan_elements/in_accel_z_en
# echo 32 > ./buffer0/length
# echo 15 > ./buffer0/watermark
# echo 1 > ./buffer0/enable
# iio_readdev -b 16 -s 21 adxl345 > samples.dat
# hexdump -d ./samples.dat
0000000 65523 00006 00248 65523 00005 00235 65522 00006
0000010 00248 65522 00006 00248 65521 00005 00247 65522
0000020 00007 00249 65523 00005 00249 65521 00006 00248
0000030 65522 00006 00248 65522 00006 00250 65522 00006
0000040 00249 65522 00005 00248 65523 00005 00248 65521
0000050 00007 00248 65521 00006 00250 65522 00005 00248
0000060 65521 00006 00248 65522 00007 00247 65522 00006
0000070 00248 65522 00006 00248 65521 00004 00250
000007e

Am I doing this actually correctly?

---
v4 -> v5:
- fix dt-binding for enum array of INT1 and INT2
v3 -> v4:
- fix dt-binding indention
v2 -> v3:
- reorganize commits, merge the watermark handling
- INT lines are defined by binding
- kfifo is prepared by devm_iio_kfifo_buffer_setup()
- event handler is registered w/ devm_request_threaded_irq()
v1 -> v2:
Fix comments according to Documentation/doc-guide/kernel-doc.rst
and missing static declaration of function.
---
Lothar Rubusch (10):
iio: accel: adxl345: refrase comment on probe
iio: accel: adxl345: rename variable data to st
iio: accel: adxl345: measure right-justified
iio: accel: adxl345: add function to switch measuring mode
iio: accel: adxl345: complete list of defines
dt-bindings: iio: accel: add interrupt-names
iio: accel: adxl345: introduce interrupt handling
iio: accel: adxl345: initialize FIFO delay value for SPI
iio: accel: adxl345: prepare channel for scan_index
iio: accel: adxl345: add FIFO with watermark events

.../bindings/iio/accel/adi,adxl345.yaml | 7 +
drivers/iio/accel/adxl345.h | 90 +++-
drivers/iio/accel/adxl345_core.c | 427 ++++++++++++++++--
drivers/iio/accel/adxl345_i2c.c | 2 +-
drivers/iio/accel/adxl345_spi.c | 7 +-
5 files changed, 478 insertions(+), 55 deletions(-)

--
2.39.2