iio: adc: ad7944: use spi_optimize_message()

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@baylibre.com>
Link: https://lore.kernel.org/r/20240328-ad7944-spi-optimize-message-v2-1-a142b2576379@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/ad7944.c b/drivers/iio/adc/ad7944.c
index 9aa3e98cd75cba9e8139c09c83c984d95a1b3b5a..9dc86ec23c36c0d379eaa8fc2f55bfc9ba5e13a3 100644 (file)
--- 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;
@@ -393,10 +409,6 @@ static int ad7944_probe(struct spi_device *spi)
        else
                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.
@@ -489,6 +501,23 @@ 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;