Add a custom implementation of regmap read/write callbacks using the SPI
bus. This allows them to be performed at a lower SCLK rate than data
reads. Previously, all SPI transfers were being performed at a lower
speed, but with this change sample data is read at the max bus speed
while the register reads/writes remain at the lower rate.
Also remove .can_multi_write from the AD4695 driver's regmap_configs, as
this isn't implemented or needed.
For some background context, see:
https://lore.kernel.org/linux-iio/20241028163907.00007e12@xxxxxxxxxx/
Suggested-by: David Lechner <dlechner@xxxxxxxxxxxx>
Signed-off-by: Trevor Gamblin <tgamblin@xxxxxxxxxxxx>
---
drivers/iio/adc/Kconfig | 2 +-
drivers/iio/adc/ad4695.c | 74 +++++++++++++++++++++++++++++++++++++++++++-----
2 files changed, 68 insertions(+), 8 deletions(-)
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 6c4e74420fd2..e0f9d01ce37d 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -51,9 +51,9 @@ config AD4130
config AD4695
tristate "Analog Device AD4695 ADC Driver"
depends on SPI
- select REGMAP_SPI
select IIO_BUFFER
select IIO_TRIGGERED_BUFFER
+ select REGMAP
help
Say yes here to build support for Analog Devices AD4695 and similar
analog to digital converters (ADC).
diff --git a/drivers/iio/adc/ad4695.c b/drivers/iio/adc/ad4695.c
index f36c1a1db886..180a0fd4f03c 100644
--- a/drivers/iio/adc/ad4695.c
+++ b/drivers/iio/adc/ad4695.c
@@ -150,6 +150,8 @@ struct ad4695_state {
/* Commands to send for single conversion. */
u16 cnv_cmd;
u8 cnv_cmd2;
+ /* Buffer for storing data from regmap bus reads/writes */
+ u8 regmap_bus_data[4];
};
static const struct regmap_range ad4695_regmap_rd_ranges[] = {
@@ -194,7 +196,6 @@ static const struct regmap_config ad4695_regmap_config = {
.max_register = AD4695_REG_AS_SLOT(127),
.rd_table = &ad4695_regmap_rd_table,
.wr_table = &ad4695_regmap_wr_table,
- .can_multi_write = true,
};
static const struct regmap_range ad4695_regmap16_rd_ranges[] = {
@@ -226,7 +227,67 @@ static const struct regmap_config ad4695_regmap16_config = {
.max_register = AD4695_REG_GAIN_IN(15),
.rd_table = &ad4695_regmap16_rd_table,
.wr_table = &ad4695_regmap16_wr_table,
- .can_multi_write = true,
+};
+
+static int ad4695_regmap_bus_reg_write(void *context, const void *data,
+ size_t count)
+{
+ struct ad4695_state *st = context;
+ struct spi_transfer xfer = {
+ .speed_hz = AD4695_REG_ACCESS_SCLK_HZ,
+ .len = count,
+ .tx_buf = st->regmap_bus_data,
+ };
+
+ if (count > ARRAY_SIZE(st->regmap_bus_data))
+ return -EINVAL;
+
+ memcpy(st->regmap_bus_data, data, count);
+
+ return spi_sync_transfer(st->spi, &xfer, 1);
+}
+
+static int ad4695_regmap_bus_reg_read(void *context, const void *reg,
+ size_t reg_size, void *val,
+ size_t val_size)
+{
+ struct ad4695_state *st = context;
+ struct spi_transfer xfers[] = {
+ {
+ .speed_hz = AD4695_REG_ACCESS_SCLK_HZ,
+ .len = reg_size,
+ .tx_buf = &st->regmap_bus_data[0],
+ }, {
+ .speed_hz = AD4695_REG_ACCESS_SCLK_HZ,
+ .len = val_size,
+ .rx_buf = &st->regmap_bus_data[2],
+ },
+ };
+ int ret;
+
+ if (reg_size > 2)
+ return -EINVAL;
+
+ if (val_size > 2)
+ return -EINVAL;
+
+ memcpy(&st->regmap_bus_data[0], reg, reg_size);
+
+ ret = spi_sync_transfer(st->spi, xfers, ARRAY_SIZE(xfers));
+ if (ret)
+ return ret;
+
+ memcpy(val, &st->regmap_bus_data[2], val_size);
+
+ return 0;
+}
+
+static const struct regmap_bus ad4695_regmap_bus = {
+ .write = ad4695_regmap_bus_reg_write,
+ .read = ad4695_regmap_bus_reg_read,
+ .read_flag_mask = 0x80,
+ .reg_format_endian_default = REGMAP_ENDIAN_BIG,
+ .val_format_endian_default = REGMAP_ENDIAN_BIG,
};
static const struct iio_chan_spec ad4695_channel_template = {
@@ -1040,15 +1101,14 @@ static int ad4695_probe(struct spi_device *spi)
if (!st->chip_info)
return -EINVAL;
- /* Registers cannot be read at the max allowable speed */
- spi->max_speed_hz = AD4695_REG_ACCESS_SCLK_HZ;
-
- st->regmap = devm_regmap_init_spi(spi, &ad4695_regmap_config);
+ st->regmap = devm_regmap_init(dev, &ad4695_regmap_bus, st,
+ &ad4695_regmap_config);
if (IS_ERR(st->regmap))
return dev_err_probe(dev, PTR_ERR(st->regmap),
"Failed to initialize regmap\n");
- st->regmap16 = devm_regmap_init_spi(spi, &ad4695_regmap16_config);
+ st->regmap16 = devm_regmap_init(dev, &ad4695_regmap_bus, st,
+ &ad4695_regmap_config);
