The AD7949 (but not the other two models supported by this driver) uses
samples 14 bits wide. When attempting to communicate through certain SPI
controllers that require power-of-2 word widths, this fails. Adding
logic to pack the 14-bit messages into the most-significant bits of a
16-bit message for communicating over byte-based SPI bus.
Only able to test with AD7949 part, but should support the 16-bit
samples of the AD7682 and AD7689, as well.
Signed-off-by: Adam Michaelis <adam.michaelis@xxxxxxxxxxxxxxxxxxx>
---
V2: Add some defines to reduce use of magic numbers.
---
drivers/iio/adc/ad7949.c | 106 +++++++++++++++++++++++++++--------------------
1 file changed, 60 insertions(+), 46 deletions(-)
diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
index 7820e1097787..cba152151908 100644
--- a/drivers/iio/adc/ad7949.c
+++ b/drivers/iio/adc/ad7949.c
@@ -33,6 +33,11 @@
#define AD7949_CFG_READBACK_DIS 1
#define AD7949_CFG_READBACK_MASK GENMASK(0, 0)
+#define AD7949_BUFFER_LEN 4
+
+#define AD7949_HI_RESOLUTION 16
+#define AD7949_LO_RESOLUTION 14
+
enum {
ID_AD7949 = 0,
ID_AD7682,
@@ -57,9 +62,9 @@ struct ad7949_adc_spec {
};
static const struct ad7949_adc_spec ad7949_adc_spec[] = {
- [ID_AD7949] = { .num_channels = 8, .resolution = 14 },
- [ID_AD7682] = { .num_channels = 4, .resolution = 16 },
- [ID_AD7689] = { .num_channels = 8, .resolution = 16 },
+ [ID_AD7949] = { .num_channels = 8, .resolution = AD7949_LO_RESOLUTION },
+ [ID_AD7682] = { .num_channels = 4, .resolution = AD7949_HI_RESOLUTION },
+ [ID_AD7689] = { .num_channels = 8, .resolution = AD7949_HI_RESOLUTION },
};
/**
@@ -85,7 +90,7 @@ struct ad7949_adc_chip {
u8 resolution;
u16 cfg;
unsigned int current_channel;
- u32 buffer ____cacheline_aligned;
+ u8 buffer[AD7949_BUFFER_LEN] ____cacheline_aligned;
};
static bool ad7949_spi_cfg_is_read_back(struct ad7949_adc_chip *ad7949_adc)
@@ -96,41 +101,51 @@ static bool ad7949_spi_cfg_is_read_back(struct ad7949_adc_chip *ad7949_adc)
return false;
}
-static int ad7949_spi_bits_per_word(struct ad7949_adc_chip *ad7949_adc)
+static int ad7949_message_len(struct ad7949_adc_chip *ad7949_adc)
{
- int ret = ad7949_adc->resolution;
+ int tx_len = 2;
if (ad7949_spi_cfg_is_read_back(ad7949_adc))
- ret += AD7949_CFG_REG_SIZE_BITS;
+ tx_len += 2;
- return ret;
+ return tx_len;
}
static int ad7949_spi_write_cfg(struct ad7949_adc_chip *ad7949_adc, u16 val,
u16 mask)
{
- int ret;
- int bits_per_word = ad7949_spi_bits_per_word(ad7949_adc);
- int shift = bits_per_word - AD7949_CFG_REG_SIZE_BITS;
+ int ret = 0;
struct spi_message msg;
- struct spi_transfer tx[] = {
- {
- .tx_buf = &ad7949_adc->buffer,
- .len = 4,
- .bits_per_word = bits_per_word,
- },
- };
-
- ad7949_adc->cfg = (val & mask) | (ad7949_adc->cfg & ~mask);
- ad7949_adc->buffer = (ad7949_adc->cfg & AD7949_CFG_MASK_TOTAL) << shift;
- spi_message_init_with_transfers(&msg, tx, 1);
- ret = spi_sync(ad7949_adc->spi, &msg);
+ struct spi_transfer tx;
+ u16 tmp_cfg = 0;
+
+ (void)memset(&tx, 0, sizeof(tx));
+ (void)memset(ad7949_adc->buffer, 0, AD7949_BUFFER_LEN);
+
+ tmp_cfg = ((val & mask) | (ad7949_adc->cfg & ~mask)) &
+ AD7949_CFG_MASK_TOTAL;
+
+ if (tmp_cfg != ad7949_adc->cfg) {
+ ad7949_adc->cfg = tmp_cfg;
+
+ /* Pack 14-bit value into 2 bytes, MSB first */
+ ad7949_adc->buffer[0] = ((ad7949_adc->cfg & 0x7f00) >> 6) |
+ ((ad7949_adc->cfg & 0xc0) >> 6);
+ ad7949_adc->buffer[1] = (ad7949_adc->cfg & 0x007f) << 2;
+
+ tx.tx_buf = ad7949_adc->buffer;
+ tx.len = ad7949_message_len(ad7949_adc);
+
+ spi_message_init_with_transfers(&msg, &tx, 1);
+ ret = spi_sync(ad7949_adc->spi, &msg);
+
+ /*
+ * This delay is to avoid a new request before the required
+ * time to send a new command to the device
+ */
+ udelay(2);
+ }
- /*
- * This delay is to avoid a new request before the required time to
- * send a new command to the device
- */
- udelay(2);
return ret;
}
@@ -138,16 +153,10 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
unsigned int channel)
{
int ret;
- int bits_per_word = ad7949_spi_bits_per_word(ad7949_adc);
- int mask = GENMASK(ad7949_adc->resolution, 0);
struct spi_message msg;
- struct spi_transfer tx[] = {
- {
- .rx_buf = &ad7949_adc->buffer,
- .len = 4,
- .bits_per_word = bits_per_word,
- },
- };
+ struct spi_transfer tx;
+
+ ad7949_adc->current_channel = channel;
ret = ad7949_spi_write_cfg(ad7949_adc,
channel << AD7949_CFG_CHAN_SEL_SHIFT,
@@ -155,24 +164,29 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
if (ret)
return ret;
- ad7949_adc->buffer = 0;
- spi_message_init_with_transfers(&msg, tx, 1);
+ (void)memset(&tx, 0, sizeof(tx));
+ (void)memset(ad7949_adc->buffer, 0, AD7949_BUFFER_LEN);
+
+ tx.rx_buf = ad7949_adc->buffer;
+ tx.len = ad7949_message_len(ad7949_adc);
+
+ spi_message_init_with_transfers(&msg, &tx, 1);
ret = spi_sync(ad7949_adc->spi, &msg);
if (ret)
return ret;
/*
- * This delay is to avoid a new request before the required time to
- * send a new command to the device
+ * This delay is to avoid a new request before the required time
+ * to send a new command to the device.
*/
udelay(2);
- ad7949_adc->current_channel = channel;
+ *val = (ad7949_adc->buffer[0] << 8) | ad7949_adc->buffer[1];
- if (ad7949_spi_cfg_is_read_back(ad7949_adc))
- *val = (ad7949_adc->buffer >> AD7949_CFG_REG_SIZE_BITS) & mask;
- else
- *val = ad7949_adc->buffer & mask;
+ if (ad7949_adc->resolution == AD7949_LO_RESOLUTION) {
+ /* 14-bit value in 16-bit buffer */
+ *val = *val >> 2;
+ }
return 0;
}
--
1.9.1
