From: Liam Beguin <lvb@xxxxxxxxxx>
This driver supports devices with 14-bit and 16-bit sample sizes.
This implies different SPI transfer lengths which are not always handled
properly by some SPI controllers.
To work around this limitation, define a big endian buffer used to split
the buffer into two 8-bit messages in the event that the controller
doesn't support 14-bit or 16-bit transfers.
A separate buffer is introduced here to avoid performing operations on
types of different endianness.
Since all transfers use the same bits_per_word value, move that logic to
the probe function, and let transfers default to the value defined in
the struct spi_device.
Signed-off-by: Liam Beguin <lvb@xxxxxxxxxx>
---
drivers/iio/adc/ad7949.c | 86 +++++++++++++++++++++++++++-------------
1 file changed, 58 insertions(+), 28 deletions(-)
diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
index adc4487a7d56..a263d0fcec75 100644
--- a/drivers/iio/adc/ad7949.c
+++ b/drivers/iio/adc/ad7949.c
@@ -14,7 +14,6 @@
#include <linux/bitfield.h>
#define AD7949_CFG_MASK_TOTAL GENMASK(13, 0)
-#define AD7949_CFG_REG_SIZE_BITS 14
/* CFG: Configuration Update */
#define AD7949_CFG_MASK_OVERWRITE BIT(13)
@@ -71,6 +70,7 @@ static const struct ad7949_adc_spec ad7949_adc_spec[] = {
* @cfg: copy of the configuration register
* @current_channel: current channel in use
* @buffer: buffer to send / receive data to / from device
+ * @buf8b: be16 buffer to exchange data with the device in 8-bit transfers
*/
struct ad7949_adc_chip {
struct mutex lock;
@@ -81,27 +81,34 @@ struct ad7949_adc_chip {
u16 cfg;
unsigned int current_channel;
u16 buffer ____cacheline_aligned;
+ __be16 buf8b;
};
static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val,
u16 mask)
{
int ret;
- int bits_per_word = ad7949_adc->resolution;
- int shift = bits_per_word - AD7949_CFG_REG_SIZE_BITS;
- struct spi_message msg;
- struct spi_transfer tx[] = {
- {
- .tx_buf = &ad7949_adc->buffer,
- .len = 2,
- .bits_per_word = bits_per_word,
- },
- };
ad7949_adc->cfg = (val & mask) | (ad7949_adc->cfg & ~mask);
- ad7949_adc->buffer = ad7949_adc->cfg << shift;
- spi_message_init_with_transfers(&msg, tx, 1);
- ret = spi_sync(ad7949_adc->spi, &msg);
+
+ switch (ad7949_adc->spi->bits_per_word) {
+ case 16:
+ ad7949_adc->buffer = ad7949_adc->cfg << 2;
+ ret = spi_write(ad7949_adc->spi, &ad7949_adc->buffer, 2);
+ break;
+ case 14:
+ ad7949_adc->buffer = ad7949_adc->cfg;
+ ret = spi_write(ad7949_adc->spi, &ad7949_adc->buffer, 2);
+ break;
+ case 8:
+ /* Here, type is big endian as it must be sent in two transfers */
+ ad7949_adc->buf8b = cpu_to_be16(ad7949_adc->cfg << 2);
+ ret = spi_write(ad7949_adc->spi, &ad7949_adc->buf8b, 2);
+ break;
+ default:
+ dev_err(&ad7949_adc->indio_dev->dev, "unsupported BPW\n");
+ return -EINVAL;
+ }
/*
* This delay is to avoid a new request before the required time to
@@ -116,16 +123,6 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
{
int ret;
int i;
- int bits_per_word = ad7949_adc->resolution;
- int mask = GENMASK(ad7949_adc->resolution - 1, 0);
- struct spi_message msg;
- struct spi_transfer tx[] = {
- {
- .rx_buf = &ad7949_adc->buffer,
- .len = 2,
- .bits_per_word = bits_per_word,
- },
- };
/*
* 1: write CFG for sample N and read old data (sample N-2)
@@ -144,9 +141,11 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
}
/* 3: write something and read actual data */
- ad7949_adc->buffer = 0;
- spi_message_init_with_transfers(&msg, tx, 1);
- ret = spi_sync(ad7949_adc->spi, &msg);
+ if (ad7949_adc->spi->bits_per_word == 8)
+ ret = spi_read(ad7949_adc->spi, &ad7949_adc->buf8b, 2);
+ else
+ ret = spi_read(ad7949_adc->spi, &ad7949_adc->buffer, 2);
+
if (ret)
return ret;
@@ -158,7 +157,25 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
ad7949_adc->current_channel = channel;
- *val = ad7949_adc->buffer & mask;
+ switch (ad7949_adc->spi->bits_per_word) {
+ case 16:
+ *val = ad7949_adc->buffer;
+ /* Shift-out padding bits */
+ *val >>= 16 - ad7949_adc->resolution;
+ break;
+ case 14:
+ *val = ad7949_adc->buffer & GENMASK(13, 0);
+ break;
+ case 8:
+ /* Here, type is big endian as data was sent in two transfers */
+ *val = be16_to_cpu(ad7949_adc->buf8b);
+ /* Shift-out padding bits */
+ *val >>= 16 - ad7949_adc->resolution;
+ break;
+ default:
+ dev_err(&ad7949_adc->indio_dev->dev, "unsupported BPW\n");
+ return -EINVAL;
+ }
return 0;
}
@@ -266,6 +283,7 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
static int ad7949_spi_probe(struct spi_device *spi)
{
+ u32 spi_ctrl_mask = spi->controller->bits_per_word_mask;
struct device *dev = &spi->dev;
const struct ad7949_adc_spec *spec;
struct ad7949_adc_chip *ad7949_adc;
@@ -292,6 +310,18 @@ static int ad7949_spi_probe(struct spi_device *spi)
indio_dev->num_channels = spec->num_channels;
ad7949_adc->resolution = spec->resolution;
+ /* Set SPI bits per word */
+ if (spi_ctrl_mask & SPI_BPW_MASK(ad7949_adc->resolution)) {
+ spi->bits_per_word = ad7949_adc->resolution;
+ } else if (spi_ctrl_mask == SPI_BPW_MASK(16)) {
+ spi->bits_per_word = 16;
+ } else if (spi_ctrl_mask == SPI_BPW_MASK(8)) {
+ spi->bits_per_word = 8;
+ } else {
+ dev_err(dev, "unable to find common BPW with spi controller\n");
+ return -EINVAL;
+ }
+
ad7949_adc->vref = devm_regulator_get(dev, "vref");
if (IS_ERR(ad7949_adc->vref)) {
dev_err(dev, "fail to request regulator\n");
--
2.32.0.452.g940fe202adcb
