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. Also, 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>
---
drivers/iio/adc/ad7476.c | 36 +++++++++++++++++++++++++++++++++++-
1 file changed, 35 insertions(+), 1 deletion(-)
diff --git a/drivers/iio/adc/ad7476.c b/drivers/iio/adc/ad7476.c
index 1f736be09663..fc98aadc4077 100644
--- a/drivers/iio/adc/ad7476.c
+++ b/drivers/iio/adc/ad7476.c
@@ -33,6 +33,7 @@ struct ad7476_chip_info {
struct iio_chan_spec convst_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;
};
@@ -64,6 +65,23 @@ static void ad7091_convst(struct ad7476_state *st)
udelay(1); /* Conversion time: 650 ns max */
}
+static void bd79105_convst_disable(struct ad7476_state *st)
+{
+ if (!st->convst_gpio)
+ return;
+
+ gpiod_set_value(st->convst_gpio, 0);
+}
+
+static void bd79105_convst_enable(struct ad7476_state *st)
+{
+ if (!st->convst_gpio)
+ return;
+
+ gpiod_set_value(st->convst_gpio, 1);
+ udelay(1); /* 10ns required for conversion */
+}
+
static irqreturn_t ad7476_trigger_handler(int irq, void *p)
{
struct iio_poll_func *pf = p;
@@ -81,6 +99,8 @@ 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;
@@ -278,6 +298,20 @@ static const struct ad7476_chip_info ltc2314_14_chip_info = {
.has_vref = true,
};
+static const struct ad7476_chip_info bd79105_chip_info = {
+ .convst_channel[0] = AD7091R_CONVST_CHAN(16),
+ .convst_channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
+ /*
+ * The BD79105 starts ADC data conversion when thw CONVSTART 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,
+ .has_vref = true,
+ .has_vdrive = true,
+};
+
static const struct iio_info ad7476_info = {
.read_raw = &ad7476_read_raw,
};
@@ -347,7 +381,6 @@ static int ad7476_probe(struct spi_device *spi)
if (st->convst_gpio)
indio_dev->channels = st->chip_info->convst_channel;
/* Setup default message */
-
st->xfer.rx_buf = &st->data;
st->xfer.len = indio_dev->channels[0].scan_type.storagebits / 8;
@@ -393,6 +426,7 @@ 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
--
2.50.1
On Wed, Aug 06, 2025 at 10:04:43AM +0300, Matti Vaittinen wrote:
> 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. Also, 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.
...
> +static void bd79105_convst_disable(struct ad7476_state *st)
> +{
> + if (!st->convst_gpio)
> + return;
Dup code, please remove.
> + gpiod_set_value(st->convst_gpio, 0);
> +}
> +
> +static void bd79105_convst_enable(struct ad7476_state *st)
> +{
> + if (!st->convst_gpio)
> + return;
With 10ns sleep in mind this is also unneeded check.
> + gpiod_set_value(st->convst_gpio, 1);
> + udelay(1); /* 10ns required for conversion */
We have ndelay(). But I believe toggling GPIO is much longer operation.
> +}
...
> @@ -347,7 +381,6 @@ static int ad7476_probe(struct spi_device *spi)
> if (st->convst_gpio)
> indio_dev->channels = st->chip_info->convst_channel;
> /* Setup default message */
> -
> st->xfer.rx_buf = &st->data;
> st->xfer.len = indio_dev->channels[0].scan_type.storagebits / 8;
Stray change.
--
With Best Regards,
Andy Shevchenko
On 06/08/2025 23:26, Andy Shevchenko wrote:
> On Wed, Aug 06, 2025 at 10:04:43AM +0300, Matti Vaittinen wrote:
>> 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. Also, 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.
>
> ...
>
>> +
>> +static void bd79105_convst_enable(struct ad7476_state *st)
>> +{
>
>> + if (!st->convst_gpio)
>> + return;
>
> With 10ns sleep in mind this is also unneeded check.
>
>> + gpiod_set_value(st->convst_gpio, 1);
>
>> + udelay(1); /* 10ns required for conversion */
>
> We have ndelay(). But I believe toggling GPIO is much longer operation.
Thanks for the review Andy.
As I replied to David, this 10nS is rubbish. I need to clarify the right
value.
Yours,
-- Matti
On Thu, Aug 7, 2025 at 9:31 AM Matti Vaittinen <mazziesaccount@gmail.com> wrote:
> On 06/08/2025 23:26, Andy Shevchenko wrote:
> > On Wed, Aug 06, 2025 at 10:04:43AM +0300, Matti Vaittinen wrote:
...
> >> +static void bd79105_convst_enable(struct ad7476_state *st)
> >> +{
> >
> >> + if (!st->convst_gpio)
> >> + return;
> >
> > With 10ns sleep in mind this is also unneeded check.
> >
> >> + gpiod_set_value(st->convst_gpio, 1);
> >
> >> + udelay(1); /* 10ns required for conversion */
> >
> > We have ndelay(). But I believe toggling GPIO is much longer operation.
>
> Thanks for the review Andy.
>
> As I replied to David, this 10nS is rubbish. I need to clarify the right
> value.
Then probably you want to call fsleep(), and if the value is few /
dozens of useconds, I would drop the check for GPIO and leave with a
small delay.
--
With Best Regards,
Andy Shevchenko
On 8/6/25 2:04 AM, Matti Vaittinen wrote:
> 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. Also, DOUT can be used also for a
Leave out one of the "also"s.
> '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>
> ---
> drivers/iio/adc/ad7476.c | 36 +++++++++++++++++++++++++++++++++++-
> 1 file changed, 35 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/adc/ad7476.c b/drivers/iio/adc/ad7476.c
> index 1f736be09663..fc98aadc4077 100644
> --- a/drivers/iio/adc/ad7476.c
> +++ b/drivers/iio/adc/ad7476.c
> @@ -33,6 +33,7 @@ struct ad7476_chip_info {
> struct iio_chan_spec convst_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;
> };
> @@ -64,6 +65,23 @@ static void ad7091_convst(struct ad7476_state *st)
> udelay(1); /* Conversion time: 650 ns max */
> }
>
> +static void bd79105_convst_disable(struct ad7476_state *st)
> +{
> + if (!st->convst_gpio)
> + return;
> +
> + gpiod_set_value(st->convst_gpio, 0);
> +}
> +
> +static void bd79105_convst_enable(struct ad7476_state *st)
> +{
> + if (!st->convst_gpio)
> + return;
> +
> + gpiod_set_value(st->convst_gpio, 1);
> + udelay(1); /* 10ns required for conversion */
So ndelay(10)?
> +}
> +
> static irqreturn_t ad7476_trigger_handler(int irq, void *p)
> {
> struct iio_poll_func *pf = p;
> @@ -81,6 +99,8 @@ 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;
> @@ -278,6 +298,20 @@ static const struct ad7476_chip_info ltc2314_14_chip_info = {
> .has_vref = true,
> };
>
> +static const struct ad7476_chip_info bd79105_chip_info = {
> + .convst_channel[0] = AD7091R_CONVST_CHAN(16),
> + .convst_channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
> + /*
> + * The BD79105 starts ADC data conversion when thw CONVSTART is set
s/thw/the/
Also s/CONVSTART/CONVSTART line/ would be a bit more clear.
> + * 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,
> + .has_vref = true,
> + .has_vdrive = true,
> +};
> +
> static const struct iio_info ad7476_info = {
> .read_raw = &ad7476_read_raw,
> };
> @@ -347,7 +381,6 @@ static int ad7476_probe(struct spi_device *spi)
> if (st->convst_gpio)
> indio_dev->channels = st->chip_info->convst_channel;
> /* Setup default message */
> -
Random whitespace change.
> st->xfer.rx_buf = &st->data;
> st->xfer.len = indio_dev->channels[0].scan_type.storagebits / 8;
>
> @@ -393,6 +426,7 @@ 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
Unrelated to this patch, but interesting that we don't also have
an of_ lookup table.
Thanks again David.
On 06/08/2025 18:23, David Lechner wrote:
> On 8/6/25 2:04 AM, Matti Vaittinen wrote:
>> 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. Also, DOUT can be used also for a
>
> Leave out one of the "also"s.
>
>> '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>
>> ---
>> drivers/iio/adc/ad7476.c | 36 +++++++++++++++++++++++++++++++++++-
>> 1 file changed, 35 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/iio/adc/ad7476.c b/drivers/iio/adc/ad7476.c
>> index 1f736be09663..fc98aadc4077 100644
>> --- a/drivers/iio/adc/ad7476.c
>> +++ b/drivers/iio/adc/ad7476.c
...
>> +
>> +static void bd79105_convst_enable(struct ad7476_state *st)
>> +{
>> + if (!st->convst_gpio)
>> + return;
>> +
>> + gpiod_set_value(st->convst_gpio, 1);
>> + udelay(1); /* 10ns required for conversion */
>
> So ndelay(10)?
Thanks for pointing this out. This delay was something I thought I must
clarify! This 10nS comment got just copied from the existing convstart,
it probably is wrong for the bd79105.
...
>> st->xfer.rx_buf = &st->data;
>> st->xfer.len = indio_dev->channels[0].scan_type.storagebits / 8;
>>
>> @@ -393,6 +426,7 @@ 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
>
> Unrelated to this patch, but interesting that we don't also have
> an of_ lookup table.
I am not sure what is the value of having the of_match table with the
SPI devices. The SPI-ID will in any case be required for the module
loading, and it can be built based on the DT compatible.
I admit I don't really know all the dirty details but, from what I can
say, the only potential use would be if this driver supported two
variants (which needed to be distinguished) with identical
chip-compatible but different vendor part. I accept all education (also)
on this matter though :)
Yours,
-- Matti
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