[PATCH v3 0/4] iio: adc: ad7124: proper clock support

[PATCH v3 0/4] iio: adc: ad7124: proper clock support

[David Lechner]

I started looking at adding some new features to the AD7124 driver and
noticed that the clock support was not quite right. The devicetree
bindings had a required "mclk" clock. MCLK is actually the name of an
internal counter in the ADC and also the name of the external clock
connection on the evaluation boards, so I guess it came from one or the
other of those. However, what the hardware actually has is a CLK pin
that can be wired up in one of three ways: not connected, input or
output. So the existing bindings making the clock required don't make
sense.

Furthermore, when looking at how this clock was being used in the
driver, I found that essentially this was being used as a way to
select the power mode of the ADC which is not at all how devicetree
bindings are supposed to work. The clock rate is fixed and the power
mode can change no matter what type of clock is being used. Again,
this just doesn't make sense.

So here is a series to fix the devicetree bindings and actually
implement proper clock support in the driver.

---
Changes in v3:
- Use %pfwP instead of %s.
- Add compile conditional to fix compiling when CONFIG_COMMON_CLK is not
  set.
- Fix conditional for enabling clock output.
- Include cleanup.h for __free().
- Add st->clk_hz and ad7124_get_fclk_hz() to handle external clock with
  rate not exactly the same as internal clock.
- Link to v2: https://lore.kernel.org/r/20250825-iio-adc-ad7124-proper-clock-support-v2-0-4dcff9db6b35@baylibre.com

Changes in v2:
- Picked up review tag.
- Wrap some long lines and tweaked some other odd line wrapping.
- Dropped mention of "hack" from comments.
- Use __free() instead of devm_ to free temporary name variable earlier.
- Link to v1: https://lore.kernel.org/r/20250724-iio-adc-ad7124-proper-clock-support-v1-0-88f35db2fcaf@baylibre.com

---
David Lechner (4):
      dt-bindings: iio: adc: adi,ad7124: fix clocks properties
      iio: adc: ad7124: do not require mclk
      iio: adc: ad7124: add external clock support
      iio: adc: ad7124: add clock output support

 .../devicetree/bindings/iio/adc/adi,ad7124.yaml    |  21 ++-
 drivers/iio/adc/ad7124.c                           | 170 ++++++++++++++++++---
 2 files changed, 165 insertions(+), 26 deletions(-)
---
base-commit: 91812d3843409c235f336f32f1c37ddc790f1e03
change-id: 20250723-iio-adc-ad7124-proper-clock-support-7249022a7349

Best regards,
-- 
David Lechner <dlechner@baylibre.com>

[PATCH v3 1/4] dt-bindings: iio: adc: adi,ad7124: fix clocks properties

[David Lechner]

Use correct clocks properties for the AD7124 family of ADCs.

These ADCs have an internal clock along with an optional external clock
that can be connected to the CLK pin. This pin can be wired up 3 ways:
1. Not connected - the internal clock is used.
2. Connected to an external clock (input) - the external clock is used.
3. Connected to the CLK pin on another ADC (output) - the internal clock
   is used on one and the other is configured for an external clock.

The new bindings describe these 3 cases by picking one of the following:
1. Omit both clocks and #clock-cells properties.
2. Include only the clocks property with a phandle to the external clock.
3. Include only the #clock-cells property on the ADC providing the output.

The clock-names property is now deprecated and should not be used. The
MCLK signal that it refers to is an internal counter in the ADC and
therefore does not make sense as a devicetree property as it can't be
connected to anything external to the ADC. Since there is only one
possible external clock, the clock-names property is not needed anyway.
Based on the implementation of the Linux driver, it looks like the
"mclk" clock was basically being used as a control to select the power
mode of the ADC, which is not something that should be done in the
devicetree.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: David Lechner <dlechner@baylibre.com>
---
 .../devicetree/bindings/iio/adc/adi,ad7124.yaml     | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7124.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7124.yaml
index 4dd5395730c10925c86782116dfd70a75d033bfb..2e3f84db6193b3d8765e2bdbd2d3175cf1892ba4 100644
--- a/Documentation/devicetree/bindings/iio/adc/adi,ad7124.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7124.yaml
@@ -28,12 +28,21 @@ properties:
 
   clocks:
     maxItems: 1
-    description: phandle to the master clock (mclk)
+    description: Optional external clock connected to the CLK pin.
 
   clock-names:
+    deprecated: true
+    description:
+      MCLK is an internal counter in the ADC. Do not use this property.
     items:
       - const: mclk
 
+  '#clock-cells':
+    description:
+      The CLK pin can be used as an output. When that is the case, include
+      this property.
+    const: 0
+
   interrupts:
     description: IRQ line for the ADC
     maxItems: 1
@@ -67,10 +76,14 @@ properties:
 required:
   - compatible
   - reg
-  - clocks
-  - clock-names
   - interrupts
 
+# Can't have both clock input and output at the same time.
+not:
+  required:
+    - '#clock-cells'
+    - clocks
+
 patternProperties:
   "^channel@([0-9]|1[0-5])$":
     $ref: adc.yaml
@@ -136,8 +149,6 @@ examples:
         interrupt-parent = <&gpio>;
         rdy-gpios = <&gpio 25 GPIO_ACTIVE_LOW>;
         refin1-supply = <&adc_vref>;
-        clocks = <&ad7124_mclk>;
-        clock-names = "mclk";
 
         #address-cells = <1>;
         #size-cells = <0>;

-- 
2.43.0

[PATCH v3 2/4] iio: adc: ad7124: do not require mclk

[David Lechner]

Make the "mclk" clock optional in the ad7124 driver. The MCLK is an
internal counter on the ADC, so it is not something that should be
coming from the devicetree. However, existing users may be using this
to essentially select the power mode of the ADC from the devicetree.
In order to not break those users, we have to keep the existing "mclk"
handling, but now it is optional.

Now, when the "mclk" clock is omitted from the devicetree, the driver
will default to the full power mode. Support for an external clock
and dynamic power mode switching can be added later if needed.

Signed-off-by: David Lechner <dlechner@baylibre.com>
---
 drivers/iio/adc/ad7124.c | 62 ++++++++++++++++++++++++++++++++++--------------
 1 file changed, 44 insertions(+), 18 deletions(-)

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index 3fc24f5fffc8f200c8656cb97f9e7f80546f688b..49003c8436463f49a47564644fd8e405579df829 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -174,7 +174,6 @@ struct ad7124_state {
 	struct ad_sigma_delta sd;
 	struct ad7124_channel *channels;
 	struct regulator *vref[4];
-	struct clk *mclk;
 	unsigned int adc_control;
 	unsigned int num_channels;
 	struct mutex cfgs_lock; /* lock for configs access */
@@ -254,7 +253,9 @@ static void ad7124_set_channel_odr(struct ad7124_state *st, unsigned int channel
 {
 	unsigned int fclk, odr_sel_bits;
 
-	fclk = clk_get_rate(st->mclk);
+	fclk = ad7124_master_clk_freq_hz[FIELD_GET(AD7124_ADC_CONTROL_POWER_MODE,
+						   st->adc_control)];
+
 	/*
 	 * FS[10:0] = fCLK / (fADC x 32) where:
 	 * fADC is the output data rate
@@ -1111,21 +1112,50 @@ static int ad7124_parse_channel_config(struct iio_dev *indio_dev,
 static int ad7124_setup(struct ad7124_state *st)
 {
 	struct device *dev = &st->sd.spi->dev;
-	unsigned int fclk, power_mode;
+	unsigned int power_mode;
+	struct clk *mclk;
 	int i, ret;
 
-	fclk = clk_get_rate(st->mclk);
-	if (!fclk)
-		return dev_err_probe(dev, -EINVAL, "Failed to get mclk rate\n");
+	/*
+	 * Always use full power mode for max performance. If needed, the driver
+	 * could be adapted to use a dynamic power mode based on the requested
+	 * output data rate.
+	 */
+	power_mode = AD7124_ADC_CONTROL_POWER_MODE_FULL;
 
-	/* The power mode changes the master clock frequency */
-	power_mode = ad7124_find_closest_match(ad7124_master_clk_freq_hz,
-					ARRAY_SIZE(ad7124_master_clk_freq_hz),
-					fclk);
-	if (fclk != ad7124_master_clk_freq_hz[power_mode]) {
-		ret = clk_set_rate(st->mclk, fclk);
-		if (ret)
-			return dev_err_probe(dev, ret, "Failed to set mclk rate\n");
+	/*
+	 * This "mclk" business is needed for backwards compatibility with old
+	 * devicetrees that specified a fake clock named "mclk" to select the
+	 * power mode.
+	 */
+	mclk = devm_clk_get_optional_enabled(dev, "mclk");
+	if (IS_ERR(mclk))
+		return dev_err_probe(dev, PTR_ERR(mclk), "Failed to get mclk\n");
+
+	if (mclk) {
+		unsigned long mclk_hz;
+
+		mclk_hz = clk_get_rate(mclk);
+		if (!mclk_hz)
+			return dev_err_probe(dev, -EINVAL,
+					     "Failed to get mclk rate\n");
+
+		/*
+		 * This logic is a bit backwards, which is why it is only here
+		 * for backwards compatibility. The driver should be able to set
+		 * the power mode as it sees fit and the f_clk/mclk rate should
+		 * be dynamic accordingly. But here, we are selecting a fixed
+		 * power mode based on the given "mclk" rate.
+		 */
+		power_mode = ad7124_find_closest_match(ad7124_master_clk_freq_hz,
+			ARRAY_SIZE(ad7124_master_clk_freq_hz), mclk_hz);
+
+		if (mclk_hz != ad7124_master_clk_freq_hz[power_mode]) {
+			ret = clk_set_rate(mclk, mclk_hz);
+			if (ret)
+				return dev_err_probe(dev, ret,
+						     "Failed to set mclk rate\n");
+		}
 	}
 
 	/* Set the power mode */
@@ -1303,10 +1333,6 @@ static int ad7124_probe(struct spi_device *spi)
 			return ret;
 	}
 
-	st->mclk = devm_clk_get_enabled(&spi->dev, "mclk");
-	if (IS_ERR(st->mclk))
-		return dev_err_probe(dev, PTR_ERR(st->mclk), "Failed to get mclk\n");
-
 	ret = ad7124_soft_reset(st);
 	if (ret < 0)
 		return ret;

-- 
2.43.0

[PATCH v3 3/4] iio: adc: ad7124: add external clock support

[David Lechner]

Add support for an external clock source to the AD7124 ADC driver.

Previously, the driver only supported using the internal clock and had
bad devicetree bindings that used a fake clock to essentially select
the power mode. This is preserved for backwards compatibility.

If the clock is not named "mclk", then we know that the devicetree is
using the correct bindings and we can configure the chip to use an
external clock source rather than internal.

Also drop a redundant comment when configuring the register fields
instead of adding more.

Signed-off-by: David Lechner <dlechner@baylibre.com>
---
 drivers/iio/adc/ad7124.c | 83 ++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 76 insertions(+), 7 deletions(-)

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index 49003c8436463f49a47564644fd8e405579df829..eb5b2028dfad0f62145edff13a24e824b05e0c13 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -18,6 +18,7 @@
 #include <linux/property.h>
 #include <linux/regulator/consumer.h>
 #include <linux/spi/spi.h>
+#include <linux/units.h>
 
 #include <linux/iio/iio.h>
 #include <linux/iio/adc/ad_sigma_delta.h>
@@ -44,6 +45,11 @@
 #define AD7124_STATUS_POR_FLAG			BIT(4)
 
 /* AD7124_ADC_CONTROL */
+#define AD7124_ADC_CONTROL_CLK_SEL		GENMASK(1, 0)
+#define AD7124_ADC_CONTROL_CLK_SEL_INT			0
+#define AD7124_ADC_CONTROL_CLK_SEL_INT_OUT		1
+#define AD7124_ADC_CONTROL_CLK_SEL_EXT			2
+#define AD7124_ADC_CONTROL_CLK_SEL_EXT_DIV4		3
 #define AD7124_ADC_CONTROL_MODE			GENMASK(5, 2)
 #define AD7124_ADC_CONTROL_MODE_CONTINUOUS		0
 #define AD7124_ADC_CONTROL_MODE_SINGLE			1
@@ -92,6 +98,8 @@
 #define AD7124_MAX_CONFIGS	8
 #define AD7124_MAX_CHANNELS	16
 
+#define AD7124_INT_CLK_HZ	614400
+
 /* AD7124 input sources */
 
 enum ad7124_ref_sel {
@@ -120,9 +128,9 @@ static const unsigned int ad7124_reg_size[] = {
 };
 
 static const int ad7124_master_clk_freq_hz[3] = {
-	[AD7124_LOW_POWER] = 76800,
-	[AD7124_MID_POWER] = 153600,
-	[AD7124_FULL_POWER] = 614400,
+	[AD7124_LOW_POWER] = AD7124_INT_CLK_HZ / 8,
+	[AD7124_MID_POWER] = AD7124_INT_CLK_HZ / 4,
+	[AD7124_FULL_POWER] = AD7124_INT_CLK_HZ,
 };
 
 static const char * const ad7124_ref_names[] = {
@@ -174,6 +182,7 @@ struct ad7124_state {
 	struct ad_sigma_delta sd;
 	struct ad7124_channel *channels;
 	struct regulator *vref[4];
+	u32 clk_hz;
 	unsigned int adc_control;
 	unsigned int num_channels;
 	struct mutex cfgs_lock; /* lock for configs access */
@@ -249,12 +258,33 @@ static int ad7124_set_mode(struct ad_sigma_delta *sd,
 	return ad_sd_write_reg(&st->sd, AD7124_ADC_CONTROL, 2, st->adc_control);
 }
 
+static u32 ad7124_get_fclk_hz(struct ad7124_state *st)
+{
+	enum ad7124_power_mode power_mode;
+	u32 fclk_hz;
+
+	power_mode = FIELD_GET(AD7124_ADC_CONTROL_POWER_MODE, st->adc_control);
+	fclk_hz = st->clk_hz;
+
+	switch (power_mode) {
+	case AD7124_LOW_POWER:
+		fclk_hz /= 8;
+		break;
+	case AD7124_MID_POWER:
+		fclk_hz /= 4;
+		break;
+	default:
+		break;
+	}
+
+	return fclk_hz;
+}
+
 static void ad7124_set_channel_odr(struct ad7124_state *st, unsigned int channel, unsigned int odr)
 {
 	unsigned int fclk, odr_sel_bits;
 
-	fclk = ad7124_master_clk_freq_hz[FIELD_GET(AD7124_ADC_CONTROL_POWER_MODE,
-						   st->adc_control)];
+	fclk = ad7124_get_fclk_hz(st);
 
 	/*
 	 * FS[10:0] = fCLK / (fADC x 32) where:
@@ -1112,7 +1142,7 @@ static int ad7124_parse_channel_config(struct iio_dev *indio_dev,
 static int ad7124_setup(struct ad7124_state *st)
 {
 	struct device *dev = &st->sd.spi->dev;
-	unsigned int power_mode;
+	unsigned int power_mode, clk_sel;
 	struct clk *mclk;
 	int i, ret;
 
@@ -1156,9 +1186,48 @@ static int ad7124_setup(struct ad7124_state *st)
 				return dev_err_probe(dev, ret,
 						     "Failed to set mclk rate\n");
 		}
+
+		clk_sel = AD7124_ADC_CONTROL_CLK_SEL_INT;
+		st->clk_hz = AD7124_INT_CLK_HZ;
+	} else {
+		struct clk *clk;
+
+		clk = devm_clk_get_optional_enabled(dev, NULL);
+		if (IS_ERR(clk))
+			return dev_err_probe(dev, PTR_ERR(clk),
+					     "Failed to get external clock\n");
+
+		if (clk) {
+			unsigned long clk_hz;
+
+			clk_hz = clk_get_rate(clk);
+			if (!clk_hz)
+				return dev_err_probe(dev, -EINVAL,
+					"Failed to get external clock rate\n");
+
+			/*
+			 * The external clock may be 4x the nominal clock rate,
+			 * in which case the ADC needs to be configured to
+			 * divide it by 4. Using MEGA is a bit arbitrary, but
+			 * the expected clock rates are either 614.4 kHz or
+			 * 2.4576 MHz, so this should work.
+			 */
+			if (clk_hz > MEGA) {
+				clk_sel = AD7124_ADC_CONTROL_CLK_SEL_EXT_DIV4;
+				st->clk_hz = clk_hz / 4;
+			} else {
+				clk_sel = AD7124_ADC_CONTROL_CLK_SEL_EXT;
+				st->clk_hz = clk_hz;
+			}
+		} else {
+			clk_sel = AD7124_ADC_CONTROL_CLK_SEL_INT;
+			st->clk_hz = AD7124_INT_CLK_HZ;
+		}
 	}
 
-	/* Set the power mode */
+	st->adc_control &= ~AD7124_ADC_CONTROL_CLK_SEL;
+	st->adc_control |= FIELD_PREP(AD7124_ADC_CONTROL_CLK_SEL, clk_sel);
+
 	st->adc_control &= ~AD7124_ADC_CONTROL_POWER_MODE;
 	st->adc_control |= FIELD_PREP(AD7124_ADC_CONTROL_POWER_MODE, power_mode);
 

-- 
2.43.0

[PATCH v3 4/4] iio: adc: ad7124: add clock output support

[David Lechner]

Add support for the AD7124's internal clock output. If the #clock-cells
property is present, turn on the internal clock output during probe.

If both the clocks and #clock-names properties are present (not allowed
by devicetree bindings), assume that an external clock is being used so
that we don't accidentally have two outputs fighting each other.

Signed-off-by: David Lechner <dlechner@baylibre.com>
---
 drivers/iio/adc/ad7124.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index eb5b2028dfad0f62145edff13a24e824b05e0c13..9b410571413429a99ea3303f49377f8a7e0ceba6 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -6,7 +6,9 @@
  */
 #include <linux/bitfield.h>
 #include <linux/bitops.h>
+#include <linux/cleanup.h>
 #include <linux/clk.h>
+#include <linux/clk-provider.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/err.h>
@@ -18,6 +20,7 @@
 #include <linux/property.h>
 #include <linux/regulator/consumer.h>
 #include <linux/spi/spi.h>
+#include <linux/sprintf.h>
 #include <linux/units.h>
 
 #include <linux/iio/iio.h>
@@ -1189,6 +1192,36 @@ static int ad7124_setup(struct ad7124_state *st)
 
 		clk_sel = AD7124_ADC_CONTROL_CLK_SEL_INT;
 		st->clk_hz = AD7124_INT_CLK_HZ;
+	} else if (!device_property_present(dev, "clocks") &&
+		   device_property_present(dev, "#clock-cells")) {
+#ifdef CONFIG_COMMON_CLK
+		struct clk_hw *clk_hw;
+
+		const char *name __free(kfree) = kasprintf(GFP_KERNEL, "%pfwP-clk",
+							   dev_fwnode(dev));
+		if (!name)
+			return -ENOMEM;
+
+		clk_hw = devm_clk_hw_register_fixed_rate(dev, name, NULL, 0,
+							 AD7124_INT_CLK_HZ);
+		if (IS_ERR(clk_hw))
+			return dev_err_probe(dev, PTR_ERR(clk_hw),
+					     "Failed to register clock provider\n");
+
+		ret = devm_of_clk_add_hw_provider(dev, of_clk_hw_simple_get,
+						  clk_hw);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					     "Failed to add clock provider\n");
+#endif
+
+		/*
+		 * Treat the clock as always on. This way we don't have to deal
+		 * with someone trying to enable/disable the clock while we are
+		 * reading samples.
+		 */
+		clk_sel = AD7124_ADC_CONTROL_CLK_SEL_INT_OUT;
+		st->clk_hz = AD7124_INT_CLK_HZ;
 	} else {
 		struct clk *clk;
 

-- 
2.43.0

Re: [PATCH v3 3/4] iio: adc: ad7124: add external clock support

[Andy Shevchenko]

On Fri, Aug 29, 2025 at 12:55 AM David Lechner <dlechner@baylibre.com> wrote:
>
> Add support for an external clock source to the AD7124 ADC driver.
>
> Previously, the driver only supported using the internal clock and had
> bad devicetree bindings that used a fake clock to essentially select
> the power mode. This is preserved for backwards compatibility.
>
> If the clock is not named "mclk", then we know that the devicetree is
> using the correct bindings and we can configure the chip to use an
> external clock source rather than internal.
>
> Also drop a redundant comment when configuring the register fields
> instead of adding more.

...

> +                       if (clk_hz > MEGA) {

I read your answer, but maybe I missed something?  Can we use (1 *
HZ_PER_MHZ) here?

> +                               clk_sel = AD7124_ADC_CONTROL_CLK_SEL_EXT_DIV4;
> +                               st->clk_hz = clk_hz / 4;
> +                       } else {
> +                               clk_sel = AD7124_ADC_CONTROL_CLK_SEL_EXT;
> +                               st->clk_hz = clk_hz;
> +                       }


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3 3/4] iio: adc: ad7124: add external clock support

[David Lechner]

On 8/29/25 10:53 AM, Andy Shevchenko wrote:
> On Fri, Aug 29, 2025 at 12:55 AM David Lechner <dlechner@baylibre.com> wrote:
>>
>> Add support for an external clock source to the AD7124 ADC driver.
>>
>> Previously, the driver only supported using the internal clock and had
>> bad devicetree bindings that used a fake clock to essentially select
>> the power mode. This is preserved for backwards compatibility.
>>
>> If the clock is not named "mclk", then we know that the devicetree is
>> using the correct bindings and we can configure the chip to use an
>> external clock source rather than internal.
>>
>> Also drop a redundant comment when configuring the register fields
>> instead of adding more.
> 
> ...
> 
>> +                       if (clk_hz > MEGA) {
> 
> I read your answer, but maybe I missed something?  Can we use (1 *
> HZ_PER_MHZ) here?

I suppose we can. But it doesn't add any additional information.
We already know we are dealing with Hz because of clk_hz and 1
is implicit. So it is just a matter of style preference. Since I
read a lot of code, I tend to prefer the minimal approach - it is
less to read and still has the same meaning.

> 
>> +                               clk_sel = AD7124_ADC_CONTROL_CLK_SEL_EXT_DIV4;
>> +                               st->clk_hz = clk_hz / 4;
>> +                       } else {
>> +                               clk_sel = AD7124_ADC_CONTROL_CLK_SEL_EXT;
>> +                               st->clk_hz = clk_hz;
>> +                       }
> 
> 

Re: [PATCH v3 3/4] iio: adc: ad7124: add external clock support

[Andy Shevchenko]

On Fri, Aug 29, 2025 at 8:19 PM David Lechner <dlechner@baylibre.com> wrote:
> On 8/29/25 10:53 AM, Andy Shevchenko wrote:
> > On Fri, Aug 29, 2025 at 12:55 AM David Lechner <dlechner@baylibre.com> wrote:

...

> >> +                       if (clk_hz > MEGA) {
> >
> > I read your answer, but maybe I missed something?  Can we use (1 *
> > HZ_PER_MHZ) here?
>
> I suppose we can. But it doesn't add any additional information.
> We already know we are dealing with Hz because of clk_hz and 1
> is implicit. So it is just a matter of style preference. Since I
> read a lot of code, I tend to prefer the minimal approach - it is
> less to read and still has the same meaning.

Physicist in me prefers pedantism in comparison of the units. We don't
compare kilometers with kilograms (maybe not the best example, though,
if you understand what I mean :-).

> >> +                               clk_sel = AD7124_ADC_CONTROL_CLK_SEL_EXT_DIV4;
> >> +                               st->clk_hz = clk_hz / 4;
> >> +                       } else {
> >> +                               clk_sel = AD7124_ADC_CONTROL_CLK_SEL_EXT;
> >> +                               st->clk_hz = clk_hz;
> >> +                       }


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3 3/4] iio: adc: ad7124: add external clock support

[Jonathan Cameron]

On Fri, 29 Aug 2025 22:11:12 +0300
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> On Fri, Aug 29, 2025 at 8:19 PM David Lechner <dlechner@baylibre.com> wrote:
> > On 8/29/25 10:53 AM, Andy Shevchenko wrote:  
> > > On Fri, Aug 29, 2025 at 12:55 AM David Lechner <dlechner@baylibre.com> wrote:  
> 
> ...
> 
> > >> +                       if (clk_hz > MEGA) {  
> > >
> > > I read your answer, but maybe I missed something?  Can we use (1 *
> > > HZ_PER_MHZ) here?  
> >
> > I suppose we can. But it doesn't add any additional information.
> > We already know we are dealing with Hz because of clk_hz and 1
> > is implicit. So it is just a matter of style preference. Since I
> > read a lot of code, I tend to prefer the minimal approach - it is
> > less to read and still has the same meaning.  
> 
> Physicist in me prefers pedantism in comparison of the units. We don't
> compare kilometers with kilograms (maybe not the best example, though,
> if you understand what I mean :-).
> 
As I don't think either of you have particularly strong opinions on this
(or at least you'll both be flexible) and I want to merge it.
I tweaked to 1 * HZ_PER_MHZ and applied the series.

Thanks,

Jonathan

> > >> +                               clk_sel = AD7124_ADC_CONTROL_CLK_SEL_EXT_DIV4;
> > >> +                               st->clk_hz = clk_hz / 4;
> > >> +                       } else {
> > >> +                               clk_sel = AD7124_ADC_CONTROL_CLK_SEL_EXT;
> > >> +                               st->clk_hz = clk_hz;
> > >> +                       }  
> 
>