On Tue, 02 Jun 2026 17:33:56 +0100 Rodrigo Alencar via B4 Relay <[email protected]> wrote:
> From: Rodrigo Alencar <[email protected]> > > Use of local SPI bus data to manage a collection of SPI transfers and > flush them to the SPI platform driver with the sync() operation. This > allows for faster handling of multiple channel DAC writes, avoiding kernel > overhead per spi_sync() call, which will be helpful when enabling > triggered buffer support. > > Signed-off-by: Rodrigo Alencar <[email protected]> Some minor stuff inline. Maybe it does make sense to adapt for a generic solution in the spi core, maybe not but most of these comments apply anyway! Jonathan > --- > drivers/iio/dac/ad5686-spi.c | 109 > +++++++++++++++++++++++++++++++------------ > drivers/iio/dac/ad5686.c | 4 +- > drivers/iio/dac/ad5686.h | 8 +++- > drivers/iio/dac/ad5696-i2c.c | 2 +- > 4 files changed, 88 insertions(+), 35 deletions(-) > > diff --git a/drivers/iio/dac/ad5686-spi.c b/drivers/iio/dac/ad5686-spi.c > index 6b6ef1d7071f..66a5a2164395 100644 > --- a/drivers/iio/dac/ad5686-spi.c > +++ b/drivers/iio/dac/ad5686-spi.c > @@ -12,59 +12,81 @@ > #include <linux/errno.h> > #include <linux/mod_devicetable.h> > #include <linux/module.h> > +#include <linux/overflow.h> > #include <linux/spi/spi.h> > > #include <asm/byteorder.h> > > #include "ad5686.h" > > +struct ad5686_spi_data { > + struct spi_message msg; > + unsigned int size; Not obvious to me what size is from the naming. Maybe this structure needs some documentation. > + unsigned int capacity; > + struct spi_transfer xfers[] __counted_by(capacity); > +}; > + > static int ad5686_spi_write(struct ad5686_state *st, > u8 cmd, u8 addr, u16 val) > { > - struct spi_device *spi = to_spi_device(st->dev); > - u8 tx_len, *buf; > + struct ad5686_spi_data *bus_data = st->bus_data; > + struct spi_transfer *xfer; > + > + if (bus_data->size >= bus_data->capacity) > + return -E2BIG; > + > + if (bus_data->size) > + bus_data->xfers[bus_data->size - 1].cs_change = 1; > + else > + spi_message_init(&bus_data->msg); > + > + xfer = &bus_data->xfers[bus_data->size]; > + xfer->rx_buf = NULL; > + xfer->cs_change = 0; These are both 'resets' to defaults and you are heavily relying on other fields in that rather complex structure never being set. Maybe initializing all the fields is simpler? > > switch (st->chip_info->regmap_type) { > case AD5310_REGMAP: > - st->data[0].d16 = cpu_to_be16(AD5310_CMD(cmd) | > - val); > - buf = &st->data[0].d8[0]; (why not use d16 here? Obviously this is original code, but applies below) > - tx_len = 2; > + st->data[bus_data->size].d16 = > + cpu_to_be16(AD5310_CMD(cmd) | val); > + xfer->tx_buf = &st->data[bus_data->size].d8[0]; > + xfer->len = 2; Following on from above on resetting xfer fields. *xfer = (struct spi_transfers) { .tx_buf = &st->data[bus_data->size].d16, .len = sizeof(&st->data[bus_data->size.d16), }; > break; > case AD5683_REGMAP: > - st->data[0].d32 = cpu_to_be32(AD5686_CMD(cmd) | > - AD5683_DATA(val)); > - buf = &st->data[0].d8[1]; > - tx_len = 3; > + st->data[bus_data->size].d32 = > + cpu_to_be32(AD5686_CMD(cmd) | AD5683_DATA(val)); > + xfer->tx_buf = &st->data[bus_data->size].d8[1]; > + xfer->len = 3; Similar use of designated initializer at small cost of clearing stuff that is clear. I doubt that matters. > break; > case AD5686_REGMAP: > - st->data[0].d32 = cpu_to_be32(AD5686_CMD(cmd) | > - AD5686_ADDR(addr) | > - val); > - buf = &st->data[0].d8[1]; > - tx_len = 3; > + st->data[bus_data->size].d32 = > + cpu_to_be32(AD5686_CMD(cmd) | AD5686_ADDR(addr) | val); > + xfer->tx_buf = &st->data[bus_data->size].d8[1]; > + xfer->len = 3; same again. > break; > default: > return -EINVAL; > } > > - return spi_write(spi, buf, tx_len); > + spi_message_add_tail(xfer, &bus_data->msg); > + bus_data->size++; > + > + return 0; > +} > + > +static int ad5686_spi_sync(struct ad5686_state *st) > +{ > + struct spi_device *spi = to_spi_device(st->dev); > + struct ad5686_spi_data *bus_data = st->bus_data; > + > + bus_data->size = 0; /* always reset, even on sync failure */ > + return spi_sync(spi, &bus_data->msg); > } > > static int ad5686_spi_read(struct ad5686_state *st, u8 addr) > { > - struct spi_transfer t[] = { > - { > - .tx_buf = &st->data[0].d8[1], > - .len = 3, > - .cs_change = 1, > - }, { > - .tx_buf = &st->data[1].d8[1], > - .rx_buf = &st->data[2].d8[1], > - .len = 3, > - }, > - }; > struct spi_device *spi = to_spi_device(st->dev); > + struct ad5686_spi_data *bus_data = st->bus_data; > + struct spi_transfer *xfer = &bus_data->xfers[0]; > u8 cmd = 0; > int ret; > > @@ -85,8 +107,18 @@ static int ad5686_spi_read(struct ad5686_state *st, u8 > addr) > AD5686_ADDR(addr)); > st->data[1].d32 = cpu_to_be32(AD5686_CMD(AD5686_CMD_NOOP)); > > - ret = spi_sync_transfer(spi, t, ARRAY_SIZE(t)); > - if (ret < 0) > + xfer[0].tx_buf = &st->data[0].d8[1]; > + xfer[0].len = 3; > + xfer[0].cs_change = 1; > + xfer[1].tx_buf = &st->data[1].d8[1]; > + xfer[1].rx_buf = &st->data[2].d8[1]; > + xfer[1].len = 3; > + xfer[1].cs_change = 0; Similar to above - I'd initialize the lot as suggested up there. Saves on effort thinking about it. Maybe the cost matters but I doubt it. > + > + spi_message_init_with_transfers(&bus_data->msg, xfer, 2); > + > + ret = spi_sync(spi, &bus_data->msg); > + if (ret) > return ret; > > return be32_to_cpu(st->data[2].d32); > @@ -95,12 +127,27 @@ static int ad5686_spi_read(struct ad5686_state *st, u8 > addr) > static const struct ad5686_bus_ops ad5686_spi_ops = { > .write = ad5686_spi_write, > .read = ad5686_spi_read, > + .sync = ad5686_spi_sync, > }; > > static int ad5686_spi_probe(struct spi_device *spi) > { > - return ad5686_probe(&spi->dev, spi_get_device_match_data(spi), > - spi->modalias, &ad5686_spi_ops); > + const struct ad5686_chip_info *info = spi_get_device_match_data(spi); > + struct ad5686_spi_data *bus_data; > + unsigned int capacity; > + > + /* read operation requires at least 2 transfers */ > + capacity = max(info->num_channels, 2); > + bus_data = devm_kzalloc(&spi->dev, > + struct_size(bus_data, xfers, capacity), > + GFP_KERNEL); > + if (!bus_data) > + return -ENOMEM; > + > + bus_data->capacity = capacity; > + > + return ad5686_probe(&spi->dev, info, spi->modalias, &ad5686_spi_ops, > + bus_data); > } > > static const struct spi_device_id ad5686_spi_id[] = {
