Since the reference voltage for this ADC is not expected to
change at runtime, determine the active reference voltage (either VREF
or VCC) during probe() and cache it in a single variable in the state
structure.

This improves the performance of ad799x_read_raw() and removes the
dependency on the regulator pointers during fast-path reads.

Suggested-by: Jonathan Cameron <jic23@kernel.org>
Suggested-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Archit Anant <architanant5@gmail.com>
---
 drivers/iio/adc/ad799x.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/iio/adc/ad799x.c b/drivers/iio/adc/ad799x.c
index 7504bcf627da..3cf7850357ab 100644
--- a/drivers/iio/adc/ad799x.c
+++ b/drivers/iio/adc/ad799x.c
@@ -30,6 +30,7 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/bitops.h>
+#include <linux/units.h>
 
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
@@ -135,6 +136,9 @@ struct ad799x_state {
 	u16				config;
 
 	unsigned int			transfer_size;
+
+	int				vref_uV;
+
 	IIO_DECLARE_BUFFER_WITH_TS(__be16, rx_buf, AD799X_MAX_CHANNELS);
 };
 
@@ -302,14 +306,7 @@ static int ad799x_read_raw(struct iio_dev *indio_dev,
 			GENMASK(chan->scan_type.realbits - 1, 0);
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
-		if (st->vref)
-			ret = regulator_get_voltage(st->vref);
-		else
-			ret = regulator_get_voltage(st->reg);
-
-		if (ret < 0)
-			return ret;
-		*val = ret / 1000;
+		*val = st->vref_uV / (MICRO / MILLI);
 		*val2 = chan->scan_type.realbits;
 		return IIO_VAL_FRACTIONAL_LOG2;
 	}
@@ -828,9 +825,20 @@ static int ad799x_probe(struct i2c_client *client)
 			ret = regulator_enable(st->vref);
 			if (ret)
 				goto error_disable_reg;
+			ret = regulator_get_voltage(st->vref);
+			if (ret < 0)
+				goto error_disable_vref;
+			st->vref_uV = ret;
 		}
 	}
 
+	if (!st->vref) {
+		ret = regulator_get_voltage(st->reg);
+		if (ret < 0)
+			goto error_disable_reg;
+		st->vref_uV = ret;
+	}
+
 	st->client = client;
 
 	indio_dev->name = id->name;
-- 
2.39.5

On Thu, Mar 26, 2026 at 11:35:28PM +0530, Archit Anant wrote:
> Since the reference voltage for this ADC is not expected to
> change at runtime, determine the active reference voltage (either VREF
> or VCC) during probe() and cache it in a single variable in the state
> structure.
> 
> This improves the performance of ad799x_read_raw() and removes the
> dependency on the regulator pointers during fast-path reads.

...

>  #include <linux/module.h>
>  #include <linux/mutex.h>
>  #include <linux/bitops.h>
> +#include <linux/units.h>

Can we have a prerequisite patch that sorts headers?

-- 
With Best Regards,
Andy Shevchenko

On Fri, Mar 27, 2026 at 12:42 AM Andy Shevchenko
<andriy.shevchenko@intel.com> wrote:
>
> On Thu, Mar 26, 2026 at 11:35:28PM +0530, Archit Anant wrote:
> > Since the reference voltage for this ADC is not expected to
> > change at runtime, determine the active reference voltage (either VREF
> > or VCC) during probe() and cache it in a single variable in the state
> > structure.
> >
> > This improves the performance of ad799x_read_raw() and removes the
> > dependency on the regulator pointers during fast-path reads.
>
> ...
>
> >  #include <linux/module.h>
> >  #include <linux/mutex.h>
> >  #include <linux/bitops.h>
> > +#include <linux/units.h>
>
> Can we have a prerequisite patch that sorts headers?

Sure, I'll add a patch that sorts the headers.

>
> --
> With Best Regards,
> Andy Shevchenko
>
>


-- 
Sincerely,
Archit Anant