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iio: adc: ad7476: Support ROHM BD79105

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The ROHM BD79105 is a simple 16-bit ADC accessible via SPI*.

The BD79105 has a CONVSTART pin, which must be set high to start the ADC
conversion. Unlike with the ad7091 and ad7091r which also have a
CONVSTART pin, the BD79105 requires that the pin must remain high also
for the duration of the SPI access.

(*) Couple of words about the SPI. The BD79105 has pins named as
CONVSTART, SCLK, DIN and DOUT. For the curious reader, DIN is not SPI
ISO.

DIN is a signal which can be used as a chip-select. When DIN is pulled
low, the ADC will output the completed measurement via DOUT as SCLK is
clocked. According to the data-sheet, the DIN can also be used for
daisy-chaining multiple ADCs. Furthermore, DOUT can be used also for a
'data-ready' -IRQ. These modes aren't supported by this driver.

Support reading ADC scale and data from the BD79105 using SPI, when DIN
is used as a chip-select.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://patch.msgid.link/6ee06d551256db9213ccbe72f44cfe9452717716.1754901948.git.mazziesaccount@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Matti Vaittinen
2025-08-11 11:52:22 +03:00
committed by Jonathan Cameron
parent 261b90763f
commit 6c27bf9bbf
1 changed files with 39 additions and 0 deletions
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39
drivers/iio/adc/ad7476.c
View File

@@ -32,8 +32,10 @@ struct ad7476_chip_info {
struct iio_chan_spec channel[2];
void (*reset)(struct ad7476_state *);
void (*conversion_pre_op)(struct ad7476_state *st);
void (*conversion_post_op)(struct ad7476_state *st);
bool has_vref;
bool has_vdrive;
bool convstart_required;
};
struct ad7476_state {
@@ -64,6 +66,18 @@ static void ad7091_convst(struct ad7476_state *st)
udelay(1); /* Conversion time: 650 ns max */
}
static void bd79105_convst_disable(struct ad7476_state *st)
{
gpiod_set_value_cansleep(st->convst_gpio, 0);
}
static void bd79105_convst_enable(struct ad7476_state *st)
{
gpiod_set_value_cansleep(st->convst_gpio, 1);
/* Worst case, 2790 ns required for conversion */
ndelay(2790);
}
static irqreturn_t ad7476_trigger_handler(int irq, void *p)
{
struct iio_poll_func *pf = p;
@@ -81,6 +95,8 @@ static irqreturn_t ad7476_trigger_handler(int irq, void *p)
iio_push_to_buffers_with_ts(indio_dev, st->data, sizeof(st->data),
iio_get_time_ns(indio_dev));
done:
if (st->chip_info->conversion_post_op)
st->chip_info->conversion_post_op(st);
iio_trigger_notify_done(indio_dev->trig);
return IRQ_HANDLED;
@@ -103,6 +119,9 @@ static int ad7476_scan_direct(struct ad7476_state *st)
if (ret)
return ret;
if (st->chip_info->conversion_post_op)
st->chip_info->conversion_post_op(st);
return be16_to_cpup((__be16 *)st->data);
}
@@ -273,6 +292,22 @@ static const struct ad7476_chip_info ltc2314_14_chip_info = {
.has_vref = true,
};
static const struct ad7476_chip_info bd79105_chip_info = {
.channel[0] = AD7091R_CHAN(16),
.channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
/*
* The BD79105 starts ADC data conversion when the CONVSTART line is
* set HIGH. The CONVSTART must be kept HIGH until the data has been
* read from the ADC.
*/
.conversion_pre_op = bd79105_convst_enable,
.conversion_post_op = bd79105_convst_disable,
/* BD79105 won't do conversion without convstart */
.convstart_required = true,
.has_vref = true,
.has_vdrive = true,
};
static const struct iio_info ad7476_info = {
.read_raw = &ad7476_read_raw,
};
@@ -332,6 +367,9 @@ static int ad7476_probe(struct spi_device *spi)
if (IS_ERR(st->convst_gpio))
return PTR_ERR(st->convst_gpio);
if (st->chip_info->convstart_required && !st->convst_gpio)
return dev_err_probe(&spi->dev, -EINVAL, "No convstart GPIO\n");
/*
* This will never happen. Unless someone changes the channel specs
* in this driver. And if someone does, without changing the loop
@@ -401,6 +439,7 @@ static const struct spi_device_id ad7476_id[] = {
{ "ads7866", (kernel_ulong_t)&ads7866_chip_info },
{ "ads7867", (kernel_ulong_t)&ads7867_chip_info },
{ "ads7868", (kernel_ulong_t)&ads7868_chip_info },
{ "bd79105", (kernel_ulong_t)&bd79105_chip_info },
/*
* The ROHM BU79100G is identical to the TI's ADS7866 from the software
* point of view. The binding document mandates the ADS7866 to be