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Fri, 27 Jun 2025 16:41:32 -0700 (PDT) From: David Lechner Date: Fri, 27 Jun 2025 18:40:03 -0500 Subject: [PATCH v2 07/11] 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: <20250627-iio-adc-ad7173-add-spi-offload-support-v2-7-f49c55599113@baylibre.com> References: <20250627-iio-adc-ad7173-add-spi-offload-support-v2-0-f49c55599113@baylibre.com> In-Reply-To: <20250627-iio-adc-ad7173-add-spi-offload-support-v2-0-f49c55599113@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=5695; i=dlechner@baylibre.com; h=from:subject:message-id; bh=UWnNQjC9xY1Xwfu0SBlWSeVKesQj5uaRhdQrBvWhhA0=; b=owEBbQGS/pANAwAKAcLMIAH/AY/AAcsmYgBoXywBjJObaNHVaWoiK2VxvYxEPhXkdoVtYA3bg od/i5eAfpuJATMEAAEKAB0WIQTsGNmeYg6D1pzYaJjCzCAB/wGPwAUCaF8sAQAKCRDCzCAB/wGP wCiFCACQ6zcWMQqtw6hEuiiyHHeH1+ZeloLoNUEIXcuGbUjkYnHLS0Po1PFxPZ7XFKns/cuunIZ 1PVB5YpfoxEhTc0kOz1Z0tTKK95g1nM7aGWH8Iom//T1fSp5q0gMzgPqmOwxIarH1kU5VX4xr43 97TGyDU526jH7dtBH5Kx0X11iUxXf/dtzyPWmiFTeV5jTxiuOV8EUg+ydanMvAOHiBoHum3Dkor 8TrRBE/gnlWBSz6h2bFPX00inWhEw7uQ5VsKxgZmyQnf9kPhF7SvmOLEtGRcw2OU6LeLgE5Y9Z3 CILib2nqlXiGfGlHyWQYYsrL3+i5ooubCUePwDrRv6KILtfq 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 | 72 ++++++++++++++++--------------= ---- include/linux/iio/adc/ad_sigma_delta.h | 3 ++ 2 files changed, 37 insertions(+), 38 deletions(-) diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_de= lta.c index d8101f5d443f957a398e66db1dad0d1f73c16078..30ae7ef6d3f9f686b0217650881= 3c689e6fb92f2 100644 --- a/drivers/iio/adc/ad_sigma_delta.c +++ b/drivers/iio/adc/ad_sigma_delta.c @@ -466,8 +466,9 @@ static int ad_sd_buffer_postenable(struct iio_dev *indi= o_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 @@ -509,6 +510,28 @@ 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); + /* For 24-bit data, there is an extra byte of padding. */ + 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; @@ -528,6 +551,7 @@ 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; } @@ -549,7 +573,10 @@ 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) @@ -559,50 +586,19 @@ static irqreturn_t ad_sd_trigger_handler(int irq, voi= d *p) const struct iio_scan_type *scan_type =3D &indio_dev->channels[0].scan_ty= pe; 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(scan_type->realbits + 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