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Fri, 20 Jun 2025 15:21:31 -0700 (PDT) From: David Lechner Date: Fri, 20 Jun 2025 17:20:11 -0500 Subject: [PATCH 5/9] iio: adc: ad_sigma_delta: use spi_optimize_message() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250620-iio-adc-ad7173-add-spi-offload-support-v1-5-0766f6297430@baylibre.com> References: <20250620-iio-adc-ad7173-add-spi-offload-support-v1-0-0766f6297430@baylibre.com> In-Reply-To: <20250620-iio-adc-ad7173-add-spi-offload-support-v1-0-0766f6297430@baylibre.com> To: Michael Hennerich , Jonathan Cameron , =?utf-8?q?Nuno_S=C3=A1?= , Andy Shevchenko , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Mark Brown Cc: linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-spi@vger.kernel.org, David Lechner X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=6152; i=dlechner@baylibre.com; h=from:subject:message-id; bh=cddbpWXqEEIcj2QjKN8G7oDTDa9572QNRGwDt6kGyjI=; b=owEBbQGS/pANAwAKAcLMIAH/AY/AAcsmYgBoVd694+e7CAINB1ltcYwO+0KLA/51zFkpHDmJC DuUjXS1TyGJATMEAAEKAB0WIQTsGNmeYg6D1pzYaJjCzCAB/wGPwAUCaFXevQAKCRDCzCAB/wGP wJ2+B/9HPYKdZ2KMqtGKaTpOky4qhHk3F2oVPdclcUbmcsqRtVz+TAtzAM4leaYSgN+MAPwzrXV EjM4wHuJB4fVUYlUJxMRK2N+CmUPCjrViQhdJlhwhTX4Zp8j2EHiwbts1okgm1p/SmOfZHj+b8r kMPEPx7dkXDmybmv3tiZCoDbDUGVBm/SZd6pBtjWxiCcNPbwFiUFLi9bNEnEJYcdP4tQMtCmvHY HtFb21omke1GTBHaEPldWWnt0VI7fDlOivjO/hG89fJVdZzhO1q4iRk2AgpClQw4LV9+mxplv/t 9G1Q12Wck0rplQ1AMe60QQj0aoDNn8z+RHcEQoacduNdsVEH X-Developer-Key: i=dlechner@baylibre.com; a=openpgp; fpr=8A73D82A6A1F509907F373881F8AF88C82F77C03 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 --- drivers/iio/adc/ad_sigma_delta.c | 74 ++++++++++++++++--------------= ---- include/linux/iio/adc/ad_sigma_delta.h | 3 ++ 2 files changed, 38 insertions(+), 39 deletions(-) diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_de= lta.c index 883cc02d4099908644af523bcf66c0178fbd0e55..a9b97f5d4107a2e1bb74877d304= 03445e9b04a44 100644 --- a/drivers/iio/adc/ad_sigma_delta.c +++ b/drivers/iio/adc/ad_sigma_delta.c @@ -458,8 +458,10 @@ EXPORT_SYMBOL_NS_GPL(ad_sigma_delta_single_conversion,= "IIO_AD_SIGMA_DELTA"); static int ad_sd_buffer_postenable(struct iio_dev *indio_dev) { struct ad_sigma_delta *sigma_delta =3D iio_device_get_drvdata(indio_dev); + const struct iio_scan_type *scan_type =3D &indio_dev->channels[0].scan_ty= pe; + struct spi_transfer *xfer =3D sigma_delta->sample_xfer; unsigned int i, slot, samples_buf_size; - unsigned int channel; + unsigned int channel, scan_size; u8 *samples_buf; int ret; =20 @@ -493,7 +495,7 @@ static int ad_sd_buffer_postenable(struct iio_dev *indi= o_dev) return ret; } =20 - samples_buf_size =3D ALIGN(slot * indio_dev->channels[0].scan_type.storag= ebits, 8); + samples_buf_size =3D ALIGN(slot * scan_type->storagebits, 8); samples_buf_size +=3D sizeof(int64_t); samples_buf =3D devm_krealloc(&sigma_delta->spi->dev, sigma_delta->sample= s_buf, samples_buf_size, GFP_KERNEL); @@ -501,6 +503,27 @@ static int ad_sd_buffer_postenable(struct iio_dev *ind= io_dev) return -ENOMEM; =20 sigma_delta->samples_buf =3D samples_buf; + scan_size =3D BITS_TO_BYTES(scan_type->realbits + scan_type->shift); + xfer[1].rx_buf =3D &sigma_delta->rx_buf[scan_size =3D=3D 3 ? 1 : 0]; + xfer[1].len =3D scan_size + (sigma_delta->status_appended ? 1 : 0); + xfer[1].cs_change =3D 1; + + if (sigma_delta->info->has_registers) { + xfer[0].tx_buf =3D &sigma_delta->sample_addr; + xfer[0].len =3D 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 =3D spi_optimize_message(sigma_delta->spi, &sigma_delta->sample_msg); + if (ret) + return ret; =20 spi_bus_lock(sigma_delta->spi->controller); sigma_delta->bus_locked =3D true; @@ -520,6 +543,7 @@ static int ad_sd_buffer_postenable(struct iio_dev *indi= o_dev) =20 err_unlock: spi_bus_unlock(sigma_delta->spi->controller); + spi_unoptimize_message(&sigma_delta->sample_msg); =20 return ret; } @@ -541,7 +565,10 @@ static int ad_sd_buffer_postdisable(struct iio_dev *in= dio_dev) =20 ad_sigma_delta_disable_all(sigma_delta); sigma_delta->bus_locked =3D 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; } =20 static irqreturn_t ad_sd_trigger_handler(int irq, void *p) @@ -550,51 +577,20 @@ static irqreturn_t ad_sd_trigger_handler(int irq, voi= d *p) struct iio_dev *indio_dev =3D pf->indio_dev; struct ad_sigma_delta *sigma_delta =3D iio_device_get_drvdata(indio_dev); u8 *data =3D 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; =20 reg_size =3D BITS_TO_BYTES(indio_dev->channels[0].scan_type.realbits + indio_dev->channels[0].scan_type.shift); + /* For 24-bit data, there is an extra byte of padding. */ + status_pos =3D reg_size + (reg_size =3D=3D 3 ? 1 : 0); =20 - if (sigma_delta->info->data_reg !=3D 0) - data_reg =3D sigma_delta->info->data_reg; - else - data_reg =3D AD_SD_REG_DATA; - - /* Status word will be appended to the sample during transfer */ - if (sigma_delta->status_appended) - transfer_size =3D reg_size + 1; - else - transfer_size =3D reg_size; - - switch (reg_size) { - case 4: - case 2: - case 1: - status_pos =3D 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[] =3D { [0][sample][sample][sample][status] } - * Keeping the first byte 0 shifts the status position by 1 byte to the = right. - */ - status_pos =3D 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_s= ize); + ret =3D spi_sync_locked(sigma_delta->spi, &sigma_delta->sample_msg); + if (ret) goto irq_handled; - } =20 /* * For devices sampling only one channel at diff --git a/include/linux/iio/adc/ad_sigma_delta.h b/include/linux/iio/adc= /ad_sigma_delta.h index 5056677c9941afadc2383febbcafeb02e23a4f44..2037bb68b44115681ff48f66b58= 0b63f50c2ea9e 100644 --- a/include/linux/iio/adc/ad_sigma_delta.h +++ b/include/linux/iio/adc/ad_sigma_delta.h @@ -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; =20 /* @@ -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; }; =20 static inline int ad_sigma_delta_set_channel(struct ad_sigma_delta *sd, --=20 2.43.0