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@baylibre.com>
Link: https://lore.kernel.org/r/20230929-ad2s1210-mainline-v3-16-fa4364281745@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
index 2b728863a3ff0550c1640458cd5ac85a8f1adee2..67d8af0dd7ae2734924ff21ad090d66a560c3a1b 100644 (file)
--- a/drivers/staging/iio/resolver/ad2s1210.c
+++ b/drivers/staging/iio/resolver/ad2s1210.c
@@ -76,7 +76,6 @@ struct ad2s1210_state {
        struct regmap *regmap;
        /** The external oscillator frequency in Hz. */
        unsigned long clkin_hz;
-       unsigned int fexcit;
        bool hysteresis;
        u8 resolution;
        /** For reading raw sample value via SPI. */
@@ -207,8 +206,6 @@ static int ad2s1210_reinit_excitation_frequency(struct ad2s1210_state *st,
        if (ret < 0)
                return ret;
 
-       st->fexcit = fexcit;
-
        /*
         * Software reset reinitializes the excitation frequency output.
         * It does not reset any of the configuration registers.
@@ -233,8 +230,22 @@ 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->clkin_hz / (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,