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iio: adc: ad_sigma_delta: use spi_optimize_message()

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Use spi_optimize_message() to improve the performance of buffered reads.

By setting up the SPI message and pre-optimizing it in the buffer
postenable callback, we can reduce overhead during each sample read.

A rough estimate shows that this reduced the CPU usage of the interrupt
handler thread from 22% to 16% using an EVAL-AD4112ARDZ board on a
DE10-Nano (measuring a single channel at the default 6.2 kHz sample
rate).

Signed-off-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Link: https://patch.msgid.link/20250701-iio-adc-ad7173-add-spi-offload-support-v3-8-42abb83e3dac@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
David Lechner
2025-07-01 16:37:56 -05:00
committed by Jonathan Cameron
parent 1519bedf88
commit db63e45a7d
2 changed files with 37 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files
drivers/iio/adc/ad_sigma_delta.c
+34 -38
View File
@@ -466,8 +466,9 @@ static int ad_sd_buffer_postenable(struct iio_dev *indio_dev)
{
struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
const struct iio_scan_type *scan_type = &indio_dev->channels[0].scan_type;
struct spi_transfer *xfer = sigma_delta->sample_xfer;
unsigned int i, slot, samples_buf_size;
unsigned int channel;
unsigned int channel, scan_size;
u8 *samples_buf;
int ret;
@@ -510,6 +511,28 @@ static int ad_sd_buffer_postenable(struct iio_dev *indio_dev)
return -ENOMEM;
sigma_delta->samples_buf = samples_buf;
scan_size = BITS_TO_BYTES(scan_type->realbits + scan_type->shift);
/* For 24-bit data, there is an extra byte of padding. */
xfer[1].rx_buf = &sigma_delta->rx_buf[scan_size == 3 ? 1 : 0];
xfer[1].len = scan_size + (sigma_delta->status_appended ? 1 : 0);
xfer[1].cs_change = 1;
if (sigma_delta->info->has_registers) {
xfer[0].tx_buf = &sigma_delta->sample_addr;
xfer[0].len = 1;
ad_sd_set_read_reg_addr(sigma_delta,
sigma_delta->info->data_reg ?: AD_SD_REG_DATA,
&sigma_delta->sample_addr);
spi_message_init_with_transfers(&sigma_delta->sample_msg, xfer, 2);
} else {
spi_message_init_with_transfers(&sigma_delta->sample_msg,
&xfer[1], 1);
}
ret = spi_optimize_message(sigma_delta->spi, &sigma_delta->sample_msg);
if (ret)
return ret;
spi_bus_lock(sigma_delta->spi->controller);
sigma_delta->bus_locked = true;
@@ -529,6 +552,7 @@ static int ad_sd_buffer_postenable(struct iio_dev *indio_dev)
err_unlock:
spi_bus_unlock(sigma_delta->spi->controller);
spi_unoptimize_message(&sigma_delta->sample_msg);
return ret;
}
@@ -550,7 +574,10 @@ static int ad_sd_buffer_postdisable(struct iio_dev *indio_dev)
ad_sigma_delta_disable_all(sigma_delta);
sigma_delta->bus_locked = false;
return spi_bus_unlock(sigma_delta->spi->controller);
spi_bus_unlock(sigma_delta->spi->controller);
spi_unoptimize_message(&sigma_delta->sample_msg);
return 0;
}
static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
@@ -560,50 +587,19 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
const struct iio_scan_type *scan_type = &indio_dev->channels[0].scan_type;
struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
u8 *data = sigma_delta->rx_buf;
unsigned int transfer_size;
unsigned int sample_size;
unsigned int sample_pos;
unsigned int status_pos;
unsigned int reg_size;
unsigned int data_reg;
int ret;
reg_size = BITS_TO_BYTES(scan_type->realbits + scan_type->shift);
/* For 24-bit data, there is an extra byte of padding. */
status_pos = reg_size + (reg_size == 3 ? 1 : 0);
if (sigma_delta->info->data_reg != 0)
data_reg = sigma_delta->info->data_reg;
else
data_reg = AD_SD_REG_DATA;
/* Status word will be appended to the sample during transfer */
if (sigma_delta->status_appended)
transfer_size = reg_size + 1;
else
transfer_size = reg_size;
switch (reg_size) {
case 4:
case 2:
case 1:
status_pos = reg_size;
ad_sd_read_reg_raw(sigma_delta, data_reg, transfer_size, &data[0]);
break;
case 3:
/*
* Data array after transfer will look like (if status is appended):
* data[] = { [0][sample][sample][sample][status] }
* Keeping the first byte 0 shifts the status position by 1 byte to the right.
*/
status_pos = reg_size + 1;
/* We store 24 bit samples in a 32 bit word. Keep the upper
* byte set to zero. */
ad_sd_read_reg_raw(sigma_delta, data_reg, transfer_size, &data[1]);
break;
default:
dev_err_ratelimited(&indio_dev->dev, "Unsupported reg_size: %u\n", reg_size);
ret = spi_sync_locked(sigma_delta->spi, &sigma_delta->sample_msg);
if (ret)
goto irq_handled;
}
/*
* For devices sampling only one channel at
include/linux/iio/adc/ad_sigma_delta.h
+3
View File
@@ -105,6 +105,8 @@ struct ad_sigma_delta {
bool status_appended;
/* map slots to channels in order to know what to expect from devices */
unsigned int *slots;
struct spi_message sample_msg;
struct spi_transfer sample_xfer[2];
u8 *samples_buf;
/*
@@ -116,6 +118,7 @@ struct ad_sigma_delta {
*/
u8 tx_buf[4] __aligned(IIO_DMA_MINALIGN);
u8 rx_buf[16] __aligned(8);
u8 sample_addr;
};
static inline int ad_sigma_delta_set_channel(struct ad_sigma_delta *sd,