[PATCH v2] iio: adc: ad7944: use spi_optimize_message()
From: David Lechner
Date: Thu Mar 28 2024 - 17:17:29 EST
This modifies the ad7944 driver to use spi_optimize_message() to reduce
CPU usage and increase the max sample rate by avoiding repeating
validation of the spi message on each transfer.
Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>
---
Changes in v2:
- Fix wrong array index in ad7944_3wire_cs_mode_init_msg()
- Fixed wrong number of xfers in ad7944_4wire_mode_init_msg()
- Link to v1: https://lore.kernel.org/r/20240325-ad7944-spi-optimize-message-v1-1-cded69b9e27f@xxxxxxxxxxxx
---
drivers/iio/adc/ad7944.c | 177 +++++++++++++++++++++++++++--------------------
1 file changed, 103 insertions(+), 74 deletions(-)
diff --git a/drivers/iio/adc/ad7944.c b/drivers/iio/adc/ad7944.c
index 261a3f645fd8..e09ab0c842d3 100644
--- a/drivers/iio/adc/ad7944.c
+++ b/drivers/iio/adc/ad7944.c
@@ -51,6 +51,8 @@ static const char * const ad7944_spi_modes[] = {
struct ad7944_adc {
struct spi_device *spi;
enum ad7944_spi_mode spi_mode;
+ struct spi_transfer xfers[3];
+ struct spi_message msg;
/* Chip-specific timing specifications. */
const struct ad7944_timing_spec *timing_spec;
/* GPIO connected to CNV pin. */
@@ -130,6 +132,88 @@ AD7944_DEFINE_CHIP_INFO(ad7985, ad7944, 16, 0);
/* fully differential */
AD7944_DEFINE_CHIP_INFO(ad7986, ad7986, 18, 1);
+static void ad7944_unoptimize_msg(void *msg)
+{
+ spi_unoptimize_message(msg);
+}
+
+static int ad7944_3wire_cs_mode_init_msg(struct device *dev, struct ad7944_adc *adc,
+ const struct iio_chan_spec *chan)
+{
+ unsigned int t_conv_ns = adc->always_turbo ? adc->timing_spec->turbo_conv_ns
+ : adc->timing_spec->conv_ns;
+ struct spi_transfer *xfers = adc->xfers;
+ int ret;
+
+ /*
+ * NB: can get better performance from some SPI controllers if we use
+ * the same bits_per_word in every transfer.
+ */
+ xfers[0].bits_per_word = chan->scan_type.realbits;
+ /*
+ * CS is tied to CNV and we need a low to high transition to start the
+ * conversion, so place CNV low for t_QUIET to prepare for this.
+ */
+ xfers[0].delay.value = T_QUIET_NS;
+ xfers[0].delay.unit = SPI_DELAY_UNIT_NSECS;
+
+ /*
+ * CS has to be high for full conversion time to avoid triggering the
+ * busy indication.
+ */
+ xfers[1].cs_off = 1;
+ xfers[1].delay.value = t_conv_ns;
+ xfers[1].delay.unit = SPI_DELAY_UNIT_NSECS;
+ xfers[1].bits_per_word = chan->scan_type.realbits;
+
+ /* Then we can read the data during the acquisition phase */
+ xfers[2].rx_buf = &adc->sample.raw;
+ xfers[2].len = BITS_TO_BYTES(chan->scan_type.storagebits);
+ xfers[2].bits_per_word = chan->scan_type.realbits;
+
+ spi_message_init_with_transfers(&adc->msg, xfers, 3);
+
+ ret = spi_optimize_message(adc->spi, &adc->msg);
+ if (ret)
+ return ret;
+
+ return devm_add_action_or_reset(dev, ad7944_unoptimize_msg, &adc->msg);
+}
+
+static int ad7944_4wire_mode_init_msg(struct device *dev, struct ad7944_adc *adc,
+ const struct iio_chan_spec *chan)
+{
+ unsigned int t_conv_ns = adc->always_turbo ? adc->timing_spec->turbo_conv_ns
+ : adc->timing_spec->conv_ns;
+ struct spi_transfer *xfers = adc->xfers;
+ int ret;
+
+ /*
+ * NB: can get better performance from some SPI controllers if we use
+ * the same bits_per_word in every transfer.
+ */
+ xfers[0].bits_per_word = chan->scan_type.realbits;
+ /*
+ * CS has to be high for full conversion time to avoid triggering the
+ * busy indication.
+ */
+ xfers[0].cs_off = 1;
+ xfers[0].delay.value = t_conv_ns;
+ xfers[0].delay.unit = SPI_DELAY_UNIT_NSECS;
+
+ xfers[1].rx_buf = &adc->sample.raw;
+ xfers[1].len = BITS_TO_BYTES(chan->scan_type.storagebits);
+ xfers[1].bits_per_word = chan->scan_type.realbits;
+
+ spi_message_init_with_transfers(&adc->msg, xfers, 2);
+
+ ret = spi_optimize_message(adc->spi, &adc->msg);
+ if (ret)
+ return ret;
+
+ return devm_add_action_or_reset(dev, ad7944_unoptimize_msg, &adc->msg);
+}
+
/*
* ad7944_3wire_cs_mode_conversion - Perform a 3-wire CS mode conversion and
* acquisition
@@ -145,48 +229,7 @@ AD7944_DEFINE_CHIP_INFO(ad7986, ad7986, 18, 1);
static int ad7944_3wire_cs_mode_conversion(struct ad7944_adc *adc,
const struct iio_chan_spec *chan)
{
- unsigned int t_conv_ns = adc->always_turbo ? adc->timing_spec->turbo_conv_ns
- : adc->timing_spec->conv_ns;
- struct spi_transfer xfers[] = {
- {
- /*
- * NB: can get better performance from some SPI
- * controllers if we use the same bits_per_word
- * in every transfer.
- */
- .bits_per_word = chan->scan_type.realbits,
- /*
- * CS is tied to CNV and we need a low to high
- * transition to start the conversion, so place CNV
- * low for t_QUIET to prepare for this.
- */
- .delay = {
- .value = T_QUIET_NS,
- .unit = SPI_DELAY_UNIT_NSECS,
- },
-
- },
- {
- .bits_per_word = chan->scan_type.realbits,
- /*
- * CS has to be high for full conversion time to avoid
- * triggering the busy indication.
- */
- .cs_off = 1,
- .delay = {
- .value = t_conv_ns,
- .unit = SPI_DELAY_UNIT_NSECS,
- },
- },
- {
- /* Then we can read the data during the acquisition phase */
- .rx_buf = &adc->sample.raw,
- .len = BITS_TO_BYTES(chan->scan_type.storagebits),
- .bits_per_word = chan->scan_type.realbits,
- },
- };
-
- return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));
+ return spi_sync(adc->spi, &adc->msg);
}
/*
@@ -200,33 +243,6 @@ static int ad7944_3wire_cs_mode_conversion(struct ad7944_adc *adc,
static int ad7944_4wire_mode_conversion(struct ad7944_adc *adc,
const struct iio_chan_spec *chan)
{
- unsigned int t_conv_ns = adc->always_turbo ? adc->timing_spec->turbo_conv_ns
- : adc->timing_spec->conv_ns;
- struct spi_transfer xfers[] = {
- {
- /*
- * NB: can get better performance from some SPI
- * controllers if we use the same bits_per_word
- * in every transfer.
- */
- .bits_per_word = chan->scan_type.realbits,
- /*
- * CS has to be high for full conversion time to avoid
- * triggering the busy indication.
- */
- .cs_off = 1,
- .delay = {
- .value = t_conv_ns,
- .unit = SPI_DELAY_UNIT_NSECS,
- },
-
- },
- {
- .rx_buf = &adc->sample.raw,
- .len = BITS_TO_BYTES(chan->scan_type.storagebits),
- .bits_per_word = chan->scan_type.realbits,
- },
- };
int ret;
/*
@@ -234,7 +250,7 @@ static int ad7944_4wire_mode_conversion(struct ad7944_adc *adc,
* and acquisition process.
*/
gpiod_set_value_cansleep(adc->cnv, 1);
- ret = spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));
+ ret = spi_sync(adc->spi, &adc->msg);
gpiod_set_value_cansleep(adc->cnv, 0);
return ret;
@@ -395,10 +411,6 @@ static int ad7944_probe(struct spi_device *spi)
adc->spi_mode = ret;
}
- if (adc->spi_mode == AD7944_SPI_MODE_CHAIN)
- return dev_err_probe(dev, -EINVAL,
- "chain mode is not implemented\n");
-
/*
* Some chips use unusual word sizes, so check now instead of waiting
* for the first xfer.
@@ -491,6 +503,23 @@ static int ad7944_probe(struct spi_device *spi)
return dev_err_probe(dev, -EINVAL,
"cannot have both chain mode and always turbo\n");
+ switch (adc->spi_mode) {
+ case AD7944_SPI_MODE_DEFAULT:
+ ret = ad7944_4wire_mode_init_msg(dev, adc, &chip_info->channels[0]);
+ if (ret)
+ return ret;
+
+ break;
+ case AD7944_SPI_MODE_SINGLE:
+ ret = ad7944_3wire_cs_mode_init_msg(dev, adc, &chip_info->channels[0]);
+ if (ret)
+ return ret;
+
+ break;
+ case AD7944_SPI_MODE_CHAIN:
+ return dev_err_probe(dev, -EINVAL, "chain mode is not implemented\n");
+ }
+
indio_dev->name = chip_info->name;
indio_dev->modes = INDIO_DIRECT_MODE;
indio_dev->info = &ad7944_iio_info;
---
base-commit: 526f7f17b651c78ead26fea7cea20948c00e47a5
change-id: 20240325-ad7944-spi-optimize-message-82debaa2a5a7
Best regards,
--
David Lechner <dlechner@xxxxxxxxxxxx>