staging: iio: resolver: ad2s1210: use devicetree to get CLKIN rate

This removes the fclkin sysfs attribute and replaces it with getting
the CLKIN clock rate using the clk subsystem (i.e. from the devicetree).

CLKIN comes from an external oscillator that is connected directly to
the AD2S1210 chip, so users of the sysfs attributes should not need to
be concerned with this.

The fclkin field (the datasheet name) is renamed to clkin_hz to be more
obvious that it is a frequency in Hz.
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20230929-ad2s1210-mainline-v3-9-fa4364281745@baylibre.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/resolver/Kconfig

@@ -7,6 +7,7 @@ menu "Resolver to digital converters"
 config AD2S1210
 	tristate "Analog Devices ad2s1210 driver"
 	depends on SPI
+	depends on COMMON_CLK
 	depends on GPIOLIB || COMPILE_TEST
 	help
 	  Say yes here to build support for Analog Devices spi resolver

drivers/staging/iio/resolver/ad2s1210.c

@@ -3,7 +3,9 @@
  * ad2s1210.c support for the ADI Resolver to Digital Converters: AD2S1210
  *
  * Copyright (c) 2010-2010 Analog Devices Inc.
+ * Copyright (c) 2023 BayLibre, SAS
  */
+#include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/gpio/consumer.h>
@@ -90,7 +92,8 @@ struct ad2s1210_state {
 	struct mutex lock;
 	struct spi_device *sdev;
 	struct gpio_desc *gpios[5];
-	unsigned int fclkin;
+	/** The external oscillator frequency in Hz. */
+	unsigned long clkin_hz;
 	unsigned int fexcit;
 	bool hysteresis;
 	u8 resolution;
@@ -165,7 +168,7 @@ int ad2s1210_update_frequency_control_word(struct ad2s1210_state *st)
 	int ret;
 	unsigned char fcw;
 
-	fcw = (unsigned char)(st->fexcit * (1 << 15) / st->fclkin);
+	fcw = (unsigned char)(st->fexcit * (1 << 15) / st->clkin_hz);
 	if (fcw < AD2S1210_MIN_FCW || fcw > AD2S1210_MAX_FCW) {
 		dev_err(&st->sdev->dev, "ad2s1210: FCW out of range\n");
 		return -ERANGE;
@@ -201,45 +204,6 @@ static inline int ad2s1210_soft_reset(struct ad2s1210_state *st)
 	return ad2s1210_config_write(st, 0x0);
 }
 
-static ssize_t ad2s1210_show_fclkin(struct device *dev,
-				    struct device_attribute *attr,
-				    char *buf)
-{
-	struct ad2s1210_state *st = iio_priv(dev_to_iio_dev(dev));
-
-	return sprintf(buf, "%u\n", st->fclkin);
-}
-
-static ssize_t ad2s1210_store_fclkin(struct device *dev,
-				     struct device_attribute *attr,
-				     const char *buf,
-				     size_t len)
-{
-	struct ad2s1210_state *st = iio_priv(dev_to_iio_dev(dev));
-	unsigned int fclkin;
-	int ret;
-
-	ret = kstrtouint(buf, 10, &fclkin);
-	if (ret)
-		return ret;
-	if (fclkin < AD2S1210_MIN_CLKIN || fclkin > AD2S1210_MAX_CLKIN) {
-		dev_err(dev, "ad2s1210: fclkin out of range\n");
-		return -EINVAL;
-	}
-
-	mutex_lock(&st->lock);
-	st->fclkin = fclkin;
-
-	ret = ad2s1210_update_frequency_control_word(st);
-	if (ret < 0)
-		goto error_ret;
-	ret = ad2s1210_soft_reset(st);
-error_ret:
-	mutex_unlock(&st->lock);
-
-	return ret < 0 ? ret : len;
-}
-
 static ssize_t ad2s1210_show_fexcit(struct device *dev,
 				    struct device_attribute *attr,
 				    char *buf)
@@ -537,7 +501,7 @@ static int ad2s1210_read_raw(struct iio_dev *indio_dev,
 			*val2 = 95874;
 			return IIO_VAL_INT_PLUS_NANO;
 		case IIO_ANGL_VEL:
-			*val = st->fclkin;
+			*val = st->clkin_hz;
 			*val2 = ad2s1210_velocity_scale[st->resolution];
 			return IIO_VAL_FRACTIONAL;
 		default:
@@ -549,8 +513,6 @@ static int ad2s1210_read_raw(struct iio_dev *indio_dev,
 	}
 }
 
-static IIO_DEVICE_ATTR(fclkin, 0644,
-		       ad2s1210_show_fclkin, ad2s1210_store_fclkin, 0);
 static IIO_DEVICE_ATTR(fexcit, 0644,
 		       ad2s1210_show_fexcit,	ad2s1210_store_fexcit, 0);
 static IIO_DEVICE_ATTR(control, 0644,
@@ -599,7 +561,6 @@ static const struct iio_chan_spec ad2s1210_channels[] = {
 };
 
 static struct attribute *ad2s1210_attributes[] = {
-	&iio_dev_attr_fclkin.dev_attr.attr,
 	&iio_dev_attr_fexcit.dev_attr.attr,
 	&iio_dev_attr_control.dev_attr.attr,
 	&iio_dev_attr_bits.dev_attr.attr,
@@ -657,6 +618,24 @@ static const struct iio_info ad2s1210_info = {
 	.attrs = &ad2s1210_attribute_group,
 };
 
+static int ad2s1210_setup_clocks(struct ad2s1210_state *st)
+{
+	struct device *dev = &st->sdev->dev;
+	struct clk *clk;
+
+	clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk), "failed to get clock\n");
+
+	st->clkin_hz = clk_get_rate(clk);
+	if (st->clkin_hz < AD2S1210_MIN_CLKIN || st->clkin_hz > AD2S1210_MAX_CLKIN)
+		return dev_err_probe(dev, -EINVAL,
+				     "clock frequency out of range: %lu\n",
+				     st->clkin_hz);
+
+	return 0;
+}
+
 static int ad2s1210_setup_gpios(struct ad2s1210_state *st)
 {
 	struct spi_device *spi = st->sdev;
@@ -695,6 +674,10 @@ static int ad2s1210_probe(struct spi_device *spi)
 	st->resolution = 12;
 	st->fexcit = AD2S1210_DEF_EXCIT;
 
+	ret = ad2s1210_setup_clocks(st);
+	if (ret < 0)
+		return ret;
+
 	ret = ad2s1210_setup_gpios(st);
 	if (ret < 0)
 		return ret;
@@ -709,13 +692,7 @@ static int ad2s1210_probe(struct spi_device *spi)
 	indio_dev->num_channels = ARRAY_SIZE(ad2s1210_channels);
 	indio_dev->name = spi_get_device_id(spi)->name;
 
-	ret = devm_iio_device_register(&spi->dev, indio_dev);
-	if (ret)
-		return ret;
-
-	st->fclkin = spi->max_speed_hz;
-
-	return 0;
+	return devm_iio_device_register(&spi->dev, indio_dev);
 }
 
 static const struct of_device_id ad2s1210_of_match[] = {