[PATCH v2 0/2] Add ADF4371 Reference Doubler and Reference Divider

[PATCH v2 0/2] Add ADF4371 Reference Doubler and Reference Divider

[Antoniu Miclaus]

This patch series add support for for reference doubler block and reference
divide by 2 clock block within the ADF4371.

The doubler is useful for increasing the PFD comparison frequency which will
result in a noise performance of the system.

The reference divide by 2 divides the reference signal by 2,
resulting in a 50% duty cycle PFD frequency.

Both features were requested from customers that purchased hundreds of adf4371
parts to use in their project. They need a way to adjust these blocks either
from userspace or devicetree.

The patch series aims to both satisfy the customer needs and be compliant with
the current kernel. The devicetree approach was chosen since these kind of
features are already present in the mainline kernel for parts such as adf4350.

Antoniu Miclaus (2):
  dt-bindings: iio: adf4371: add rdiv2 and doubler
  iio: frequency: adf4371: add ref doubler and div2

 .../bindings/iio/frequency/adf4371.yaml       | 11 ++++++
 drivers/iio/frequency/adf4371.c               | 35 +++++++++++++++++--
 2 files changed, 44 insertions(+), 2 deletions(-)

-- 
2.47.0

[PATCH v2 1/2] dt-bindings: iio: adf4371: add rdiv2 and doubler

[Antoniu Miclaus]

Add support for reference doubler enable and reference divide by 2
clock.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
---
no changes in v2. (added cover letter as requested)
 .../devicetree/bindings/iio/frequency/adf4371.yaml    | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/frequency/adf4371.yaml b/Documentation/devicetree/bindings/iio/frequency/adf4371.yaml
index 1cb2adaf66f9..ef241c38520c 100644
--- a/Documentation/devicetree/bindings/iio/frequency/adf4371.yaml
+++ b/Documentation/devicetree/bindings/iio/frequency/adf4371.yaml
@@ -40,6 +40,17 @@ properties:
       output stage will shut down until the ADF4371/ADF4372 achieves lock as
       measured by the digital lock detect circuitry.
 
+  adi,reference-doubler-enable:
+    type: boolean
+    description:
+      If this property is present, the reference doubler block is enabled.
+
+  adi,adi,reference-div2-enable:
+    type: boolean
+    description:
+      If this property is present, the reference divide by 2 clock is enabled.
+      This feature can be used to provide a 50% duty cycle signal to the PFD.
+
 required:
   - compatible
   - reg
-- 
2.47.0

Re: [PATCH v2 1/2] dt-bindings: iio: adf4371: add rdiv2 and doubler

[Conor Dooley]

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On Mon, Nov 25, 2024 at 01:26:40PM +0200, Antoniu Miclaus wrote:
> Add support for reference doubler enable and reference divide by 2
> clock.

You're still missing an explanation here for why these cannot be derived
from the required output frequency vs the input frequency.

> 
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
> ---
> no changes in v2. (added cover letter as requested)
>  .../devicetree/bindings/iio/frequency/adf4371.yaml    | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/frequency/adf4371.yaml b/Documentation/devicetree/bindings/iio/frequency/adf4371.yaml
> index 1cb2adaf66f9..ef241c38520c 100644
> --- a/Documentation/devicetree/bindings/iio/frequency/adf4371.yaml
> +++ b/Documentation/devicetree/bindings/iio/frequency/adf4371.yaml
> @@ -40,6 +40,17 @@ properties:
>        output stage will shut down until the ADF4371/ADF4372 achieves lock as
>        measured by the digital lock detect circuitry.
>  
> +  adi,reference-doubler-enable:
> +    type: boolean
> +    description:
> +      If this property is present, the reference doubler block is enabled.
> +
> +  adi,adi,reference-div2-enable:
> +    type: boolean
> +    description:
> +      If this property is present, the reference divide by 2 clock is enabled.
> +      This feature can be used to provide a 50% duty cycle signal to the PFD.
> +
>  required:
>    - compatible
>    - reg
> -- 
> 2.47.0
> 

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[PATCH v2 2/2] iio: frequency: adf4371: add ref doubler and div2

[Antoniu Miclaus]

Add support for the reference doubler and the reference divide by 2
clock.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
---
changes in v2:
 - assign directly `device_property_read_bool`
 - use struct device *dev = &st->spi->dev;
 drivers/iio/frequency/adf4371.c | 34 +++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/frequency/adf4371.c b/drivers/iio/frequency/adf4371.c
index b27088464826..b643a08f06ed 100644
--- a/drivers/iio/frequency/adf4371.c
+++ b/drivers/iio/frequency/adf4371.c
@@ -41,6 +41,12 @@
 #define ADF4371_MOD2WORD_MSK		GENMASK(5, 0)
 #define ADF4371_MOD2WORD(x)		FIELD_PREP(ADF4371_MOD2WORD_MSK, x)
 
+/* ADF4371_REG22 */
+#define ADF4371_REF_DOUB_MASK		BIT(5)
+#define ADF4371_REF_DOUB(x)		FIELD_PREP(ADF4371_REF_DOUB_MASK, x)
+#define ADF4371_RDIV2_MASK		BIT(4)
+#define ADF4371_RDIV2(x)		FIELD_PREP(ADF4371_RDIV2_MASK, x)
+
 /* ADF4371_REG24 */
 #define ADF4371_RF_DIV_SEL_MSK		GENMASK(6, 4)
 #define ADF4371_RF_DIV_SEL(x)		FIELD_PREP(ADF4371_RF_DIV_SEL_MSK, x)
@@ -70,6 +76,9 @@
 #define ADF4371_MAX_FREQ_PFD		250000000UL /* Hz */
 #define ADF4371_MAX_FREQ_REFIN		600000000UL /* Hz */
 
+#define ADF4371_MIN_CLKIN_DOUB_FREQ	10000000ULL /* Hz */
+#define ADF4371_MAX_CLKIN_DOUB_FREQ	125000000ULL /* Hz */
+
 /* MOD1 is a 24-bit primary modulus with fixed value of 2^25 */
 #define ADF4371_MODULUS1		33554432ULL
 /* MOD2 is the programmable, 14-bit auxiliary fractional modulus */
@@ -175,6 +184,8 @@ struct adf4371_state {
 	unsigned int mod2;
 	unsigned int rf_div_sel;
 	unsigned int ref_div_factor;
+	bool ref_doubler_en;
+	bool ref_div2_en;
 	u8 buf[10] __aligned(IIO_DMA_MINALIGN);
 };
 
@@ -476,6 +487,7 @@ static int adf4371_setup(struct adf4371_state *st)
 {
 	unsigned int synth_timeout = 2, timeout = 1, vco_alc_timeout = 1;
 	unsigned int vco_band_div, tmp;
+	struct device *dev = &st->spi->dev;
 	int ret;
 
 	/* Perform a software reset */
@@ -497,22 +509,40 @@ static int adf4371_setup(struct adf4371_state *st)
 			return ret;
 	}
 
+	st->ref_doubler_en = device_property_read_bool(dev, "adi,reference-doubler-enable");
+
+	st->ref_div2_en = device_property_read_bool(dev, "adi,reference-div2-enable");
+
 	/* Set address in ascending order, so the bulk_write() will work */
 	ret = regmap_update_bits(st->regmap, ADF4371_REG(0x0),
 				 ADF4371_ADDR_ASC_MSK | ADF4371_ADDR_ASC_R_MSK,
 				 ADF4371_ADDR_ASC(1) | ADF4371_ADDR_ASC_R(1));
 	if (ret < 0)
 		return ret;
+
+	if (st->ref_doubler_en &&
+	    (st->clkin_freq > ADF4371_MAX_CLKIN_DOUB_FREQ ||
+	     st->clkin_freq < ADF4371_MIN_CLKIN_DOUB_FREQ))
+		st->ref_doubler_en = false;
+
+	ret = regmap_update_bits(st->regmap,  ADF4371_REG(0x22),
+				 ADF4371_REF_DOUB_MASK |
+				 ADF4371_RDIV2_MASK,
+				 ADF4371_REF_DOUB(st->ref_doubler_en) |
+				 ADF4371_RDIV2(st->ref_div2_en));
+	if (ret < 0)
+		return ret;
+
 	/*
 	 * Calculate and maximize PFD frequency
 	 * fPFD = REFIN × ((1 + D)/(R × (1 + T)))
 	 * Where D is the REFIN doubler bit, T is the reference divide by 2,
 	 * R is the reference division factor
-	 * TODO: it is assumed D and T equal 0.
 	 */
 	do {
 		st->ref_div_factor++;
-		st->fpfd = st->clkin_freq / st->ref_div_factor;
+		st->fpfd = (st->clkin_freq * (st->ref_doubler_en ? 2 : 1)) /
+			   (st->ref_div_factor * (st->ref_div2_en ? 2 : 1));
 	} while (st->fpfd > ADF4371_MAX_FREQ_PFD);
 
 	/* Calculate Timeouts */
-- 
2.47.0