linux-kernel - [PATCH v2 15/19] staging: iio: resolver: ad2s1210: read excitation frequency from control register

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Date:   Thu, 21 Sep 2023 09:43:56 -0500
From:   David Lechner <dlechner@...libre.com>
To:     linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-staging@...ts.linux.dev
Cc:     linux-kernel@...r.kernel.org, Jonathan Cameron <jic23@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Nuno Sá <nuno.sa@...log.com>,
        Axel Haslam <ahaslam@...libre.com>,
        Philip Molloy <pmolloy@...libre.com>,
        David Lechner <dlechner@...libre.com>
Subject: [PATCH v2 15/19] staging: iio: resolver: ad2s1210: read excitation frequency from control register

This modifies the ad2s1210_show_fexcit() function to read the excitation
frequency from the control register. This way we don't have to keep
track of the value and don't risk returning a stale value.

Signed-off-by: David Lechner <dlechner@...libre.com>
---
 drivers/staging/iio/resolver/ad2s1210.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
index f1ffee34ebbc..27294eff99ef 100644
--- a/drivers/staging/iio/resolver/ad2s1210.c
+++ b/drivers/staging/iio/resolver/ad2s1210.c
@@ -78,7 +78,6 @@ struct ad2s1210_state {
 	struct regmap *regmap;
 	/** The external oscillator frequency in Hz. */
 	unsigned long fclkin;
-	unsigned int fexcit;
 	u8 resolution;
 	u8 rx[2] __aligned(IIO_DMA_MINALIGN);
 	u8 tx[2];
@@ -202,8 +201,6 @@ static int ad2s1210_set_excitation_frequency(struct ad2s1210_state *st,
 	if (ret < 0)
 		return ret;
 
-	st->fexcit = fexcit;
-
 	/* software reset reinitializes the excitation frequency output */
 	return regmap_write(st->regmap, AD2S1210_REG_SOFT_RESET, 0);
 }
@@ -225,8 +222,22 @@ static ssize_t ad2s1210_show_fexcit(struct device *dev,
 				    char *buf)
 {
 	struct ad2s1210_state *st = iio_priv(dev_to_iio_dev(dev));
+	unsigned int value;
+	u16 fexcit;
+	int ret;
 
-	return sprintf(buf, "%u\n", st->fexcit);
+	mutex_lock(&st->lock);
+	ret = regmap_read(st->regmap, AD2S1210_REG_EXCIT_FREQ, &value);
+	if (ret < 0)
+		goto error_ret;
+
+	fexcit = value * st->fclkin / (1 << 15);
+
+	ret = sprintf(buf, "%u\n", fexcit);
+
+error_ret:
+	mutex_unlock(&st->lock);
+	return ret;
 }
 
 static ssize_t ad2s1210_store_fexcit(struct device *dev,
-- 
2.34.1