linux-kernel - [PATCH v2 4/4] iio: adc: ad7124: add clock output support

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Message-Id: <20250825-iio-adc-ad7124-proper-clock-support-v2-4-4dcff9db6b35@baylibre.com>
Date: Mon, 25 Aug 2025 17:55:03 -0500
From: David Lechner <dlechner@...libre.com>
To: Michael Hennerich <Michael.Hennerich@...log.com>, 
 Jonathan Cameron <jic23@...nel.org>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, David Lechner <dlechner@...libre.com>
Subject: [PATCH v2 4/4] iio: adc: ad7124: add clock output support

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@...libre.com>
---

We could make this fancier and only turn on the output on demand of a
clock consumer, but then we have to deal with locking of the SPI bus
to be able to write to the register. So I opted for the simpler
solution of always turning it on during probe. This would only be used
for synchronizing with other similar ADCs, so implementing the functions
for a more general-purpose clock seems a bit overkill.
---
 drivers/iio/adc/ad7124.c | 37 ++++++++++++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index 4112c484c2371cfa6f26acb0d7c5b2a308a5fb35..a1c5f059b284c4f8797986628b92b70fd84e90f4 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -7,6 +7,7 @@
 #include <linux/bitfield.h>
 #include <linux/bitops.h>
 #include <linux/clk.h>
+#include <linux/clk-provider.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/err.h>
@@ -18,6 +19,7 @@
 #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>
@@ -125,10 +127,12 @@ static const unsigned int ad7124_reg_size[] = {
 	3, 3, 3, 3, 3
 };
 
+#define AD7124_INT_CLK_HZ 614400
+
 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[] = {
@@ -1164,6 +1168,33 @@ static int ad7124_setup(struct ad7124_state *st)
 		}
 
 		clk_sel = AD7124_ADC_CONTROL_CLK_SEL_INT;
+	} else if (!device_property_present(dev, "clocks") &&
+		   device_property_present(dev, "clock-names")) {
+		struct clk_hw *clk_hw;
+
+		const char *name __free(kfree) = kasprintf(GFP_KERNEL, "%s-clk",
+			fwnode_get_name(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");
+
+		/*
+		 * 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;
 	} else {
 		struct clk *clk;
 

-- 
2.43.0