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iio: adc: ad4695: add custom regmap bus callbacks

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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@Huawei.com/

Suggested-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Tested-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20241113-tgamblin-ad4695_improvements-v2-3-b6bb7c758fc4@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Trevor Gamblin
2024-11-13 15:53:00 -05:00
committed by Jonathan Cameron
parent 998d20e4e9
commit 1093f83b2c
2 changed files with 68 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/iio/adc/Kconfig
View File

@@ -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).

74
drivers/iio/adc/ad4695.c
View File

@@ -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 = {
@@ -1061,15 +1122,14 @@ 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_regmap16_config);
if (IS_ERR(st->regmap16))
return dev_err_probe(dev, PTR_ERR(st->regmap16),
"Failed to initialize regmap16\n");