iio: accel: adxl345: initialize FIFO delay value for SPI

Add the possibility to delay FIFO access when SPI is used. According to
the datasheet this is needed for the adxl345. When initialization
happens over SPI the need for delay is to be signalized, and the delay
will be used.

Signed-off-by: Lothar Rubusch <l.rubusch@gmail.com>
Link: https://patch.msgid.link/20241228232949.72487-3-l.rubusch@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/accel/adxl345.h b/drivers/iio/accel/adxl345.h
index 3d5c8719db3d78204305a0885c37369303198bff..6f39f16d3e084cb6fe84560bd3dfe11f495a88f3 100644 (file)
--- a/drivers/iio/accel/adxl345.h
+++ b/drivers/iio/accel/adxl345.h
@@ -62,6 +62,7 @@ struct adxl345_chip_info {
 };
 
 int adxl345_core_probe(struct device *dev, struct regmap *regmap,
+                      bool fifo_delay_default,
                       int (*setup)(struct device*, struct regmap*));
 
 #endif /* _ADXL345_H_ */

diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
index 11fdb21d5477a7b3eced8d78912df5de6989b410..58892c66429e72c3ca6abc9d2561491cd6620854 100644 (file)
--- a/drivers/iio/accel/adxl345_core.c
+++ b/drivers/iio/accel/adxl345_core.c
@@ -25,6 +25,7 @@
 struct adxl345_state {
        const struct adxl345_chip_info *info;
        struct regmap *regmap;
+       bool fifo_delay; /* delay: delay is needed for SPI */
        int irq;
        u8 intio;
 };
@@ -196,12 +197,21 @@ static const struct iio_info adxl345_info = {
  * adxl345_core_probe() - Probe and setup for the accelerometer.
  * @dev:       Driver model representation of the device
  * @regmap:    Regmap instance for the device
+ * @fifo_delay_default: Using FIFO with SPI needs delay
  * @setup:     Setup routine to be executed right before the standard device
  *             setup
  *
+ * For SPI operation greater than 1.6 MHz, it is necessary to deassert the CS
+ * pin to ensure a total delay of 5 us; otherwise, the delay is not sufficient.
+ * The total delay necessary for 5 MHz operation is at most 3.4 us. This is not
+ * a concern when using I2C mode because the communication rate is low enough
+ * to ensure a sufficient delay between FIFO reads.
+ * Ref: "Retrieving Data from FIFO", p. 21 of 36, Data Sheet ADXL345 Rev. G
+ *
  * Return: 0 on success, negative errno on error
  */
 int adxl345_core_probe(struct device *dev, struct regmap *regmap,
+                      bool fifo_delay_default,
                       int (*setup)(struct device*, struct regmap*))
 {
        struct adxl345_state *st;
@@ -222,6 +232,7 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
        st->info = device_get_match_data(dev);
        if (!st->info)
                return -ENODEV;
+       st->fifo_delay = fifo_delay_default;
 
        indio_dev->name = st->info->name;
        indio_dev->info = &adxl345_info;

diff --git a/drivers/iio/accel/adxl345_i2c.c b/drivers/iio/accel/adxl345_i2c.c
index cb23fb11fcd7d8e8595a620cd28e3abb55e6dae5..8c385dd6c01dc558866ca239295f7c7a95b4bb7b 100644 (file)
--- a/drivers/iio/accel/adxl345_i2c.c
+++ b/drivers/iio/accel/adxl345_i2c.c
@@ -27,7 +27,7 @@ static int adxl345_i2c_probe(struct i2c_client *client)
        if (IS_ERR(regmap))
                return dev_err_probe(&client->dev, PTR_ERR(regmap), "Error initializing regmap\n");
 
-       return adxl345_core_probe(&client->dev, regmap, NULL);
+       return adxl345_core_probe(&client->dev, regmap, false, NULL);
 }
 
 static const struct adxl345_chip_info adxl345_i2c_info = {

diff --git a/drivers/iio/accel/adxl345_spi.c b/drivers/iio/accel/adxl345_spi.c
index 968e7b390d4bb6719f6487ac310b12ff1a2a58e3..7e518aea17bf9f9d4196bfc366290e7fb0b1b3f6 100644 (file)
--- a/drivers/iio/accel/adxl345_spi.c
+++ b/drivers/iio/accel/adxl345_spi.c
@@ -12,6 +12,7 @@
 #include "adxl345.h"
 
 #define ADXL345_MAX_SPI_FREQ_HZ                5000000
+#define ADXL345_MAX_FREQ_NO_FIFO_DELAY 1500000
 
 static const struct regmap_config adxl345_spi_regmap_config = {
        .reg_bits = 8,
@@ -28,6 +29,7 @@ static int adxl345_spi_setup(struct device *dev, struct regmap *regmap)
 static int adxl345_spi_probe(struct spi_device *spi)
 {
        struct regmap *regmap;
+       bool needs_delay;
 
        /* Bail out if max_speed_hz exceeds 5 MHz */
        if (spi->max_speed_hz > ADXL345_MAX_SPI_FREQ_HZ)
@@ -38,10 +40,11 @@ static int adxl345_spi_probe(struct spi_device *spi)
        if (IS_ERR(regmap))
                return dev_err_probe(&spi->dev, PTR_ERR(regmap), "Error initializing regmap\n");
 
+       needs_delay = spi->max_speed_hz > ADXL345_MAX_FREQ_NO_FIFO_DELAY;
        if (spi->mode & SPI_3WIRE)
-               return adxl345_core_probe(&spi->dev, regmap, adxl345_spi_setup);
+               return adxl345_core_probe(&spi->dev, regmap, needs_delay, adxl345_spi_setup);
        else
-               return adxl345_core_probe(&spi->dev, regmap, NULL);
+               return adxl345_core_probe(&spi->dev, regmap, needs_delay, NULL);
 }
 
 static const struct adxl345_chip_info adxl345_spi_info = {