iio: accel: adxl345: add FIFO with watermark events

Add a basic setup for FIFO with configurable watermark. Add a handler
for watermark interrupt events and extend the channel for the
scan_index needed for the iio channel. The sensor is configurable to use
a FIFO_BYPASSED mode or a FIFO_STREAM mode. For the FIFO_STREAM mode now
a watermark can be configured, or disabled by setting 0. Further features
require a working FIFO setup.

Signed-off-by: Lothar Rubusch <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jonathan Cameron <[email protected]>

Author: Rubusch

drivers/iio/accel/adxl345.h

@@ -15,18 +15,31 @@
 #define ADXL345_REG_OFS_AXIS(index)	(ADXL345_REG_OFSX + (index))
 #define ADXL345_REG_BW_RATE		0x2C
 #define ADXL345_REG_POWER_CTL		0x2D
+#define ADXL345_REG_INT_ENABLE		0x2E
+#define ADXL345_REG_INT_MAP		0x2F
+#define ADXL345_REG_INT_SOURCE		0x30
+#define ADXL345_REG_INT_SOURCE_MSK	0xFF
 #define ADXL345_REG_DATA_FORMAT		0x31
-#define ADXL345_REG_DATAX0		0x32
-#define ADXL345_REG_DATAY0		0x34
-#define ADXL345_REG_DATAZ0		0x36
-#define ADXL345_REG_DATA_AXIS(index)	\
-	(ADXL345_REG_DATAX0 + (index) * sizeof(__le16))
+#define ADXL345_REG_XYZ_BASE		0x32
+#define ADXL345_REG_DATA_AXIS(index)				\
+	(ADXL345_REG_XYZ_BASE + (index) * sizeof(__le16))
 
+#define ADXL345_REG_FIFO_CTL		0x38
+#define ADXL345_FIFO_CTL_SAMPLES_MSK	GENMASK(4, 0)
+/* 0: INT1, 1: INT2 */
+#define ADXL345_FIFO_CTL_TRIGGER_MSK	BIT(5)
+#define ADXL345_FIFO_CTL_MODE_MSK	GENMASK(7, 6)
+#define ADXL345_REG_FIFO_STATUS	0x39
+#define ADXL345_REG_FIFO_STATUS_MSK	0x3F
+
+#define ADXL345_INT_OVERRUN		BIT(0)
+#define ADXL345_INT_WATERMARK		BIT(1)
+#define ADXL345_INT_DATA_READY		BIT(7)
 #define ADXL345_BW_RATE			GENMASK(3, 0)
 #define ADXL345_BASE_RATE_NANO_HZ	97656250LL
 
-#define ADXL345_POWER_CTL_MEASURE	BIT(3)
 #define ADXL345_POWER_CTL_STANDBY	0x00
+#define ADXL345_POWER_CTL_MEASURE	BIT(3)
 
 #define ADXL345_DATA_FORMAT_RANGE	GENMASK(1, 0)	/* Set the g range */
 #define ADXL345_DATA_FORMAT_JUSTIFY	BIT(2)	/* Left-justified (MSB) mode */
@@ -40,6 +53,7 @@
 #define ADXL345_DATA_FORMAT_16G		3
 
 #define ADXL345_DEVID			0xE5
+#define ADXL345_FIFO_SIZE		32
 
 /*
  * In full-resolution mode, scale factor is maintained at ~4 mg/LSB