staging: iio: resolver: ad2s1210: convert resolution to devicetree property

Selecting the resolution was implemented as the `bits` sysfs attribute.
However, the selection of the resolution depends on how the hardware
is wired and the specific application, so this is rather a job for
devicetree to describe.

A new devicetree property `assigned-resolution-bits` to specify the
resolution required for each chip is added and the `bits` sysfs
attribute is removed.

Since the resolution is now supplied by a devicetree property, the
resolution-gpios are now optional and we can allow for the case where
the resolution pins on the AD2S1210 are hard-wired instead of requiring
them to be connected to gpios.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20231005-ad2s1210-mainline-v4-4-ec00746840fc@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 0c77727253309b0561306bd4516d5dcaf321e9f7..66ef35fbb6fe9ad039c04a1bd3b929feed621cf0 100644 (file)
--- a/drivers/staging/iio/resolver/ad2s1210.c
+++ b/drivers/staging/iio/resolver/ad2s1210.c
@@ -63,6 +63,13 @@ enum ad2s1210_mode {
        MOD_CONFIG = 0b11,
 };
 
+enum ad2s1210_resolution {
+       AD2S1210_RES_10 = 0b00,
+       AD2S1210_RES_12 = 0b01,
+       AD2S1210_RES_14 = 0b10,
+       AD2S1210_RES_16 = 0b11,
+};
+
 struct ad2s1210_state {
        struct mutex lock;
        struct spi_device *sdev;
@@ -70,15 +77,14 @@ struct ad2s1210_state {
        struct gpio_desc *sample_gpio;
        /** GPIO pins connected to A0 and A1 lines. */
        struct gpio_descs *mode_gpios;
-       /** GPIO pins connected to RES0 and RES1 lines. */
-       struct gpio_descs *resolution_gpios;
        /** Used to access config registers. */
        struct regmap *regmap;
        /** The external oscillator frequency in Hz. */
        unsigned long clkin_hz;
        /** Available raw hysteresis values based on resolution. */
        int hysteresis_available[2];
-       u8 resolution;
+       /** The selected resolution */
+       enum ad2s1210_resolution resolution;
        /** For reading raw sample value via SPI. */
        __be16 sample __aligned(IIO_DMA_MINALIGN);
        /** SPI transmit buffer. */
@@ -215,63 +221,6 @@ static int ad2s1210_reinit_excitation_frequency(struct ad2s1210_state *st,
        return regmap_write(st->regmap, AD2S1210_REG_SOFT_RESET, 0);
 }
 
-static int ad2s1210_set_resolution_gpios(struct ad2s1210_state *st,
-                                        u8 resolution)
-{
-       struct gpio_descs *gpios = st->resolution_gpios;
-       DECLARE_BITMAP(bitmap, 2);
-
-       bitmap[0] = (resolution - 10) >> 1;
-
-       return gpiod_set_array_value(gpios->ndescs, gpios->desc, gpios->info,
-                                    bitmap);
-}
-
-static ssize_t ad2s1210_show_resolution(struct device *dev,
-                                       struct device_attribute *attr,
-                                       char *buf)
-{
-       struct ad2s1210_state *st = iio_priv(dev_to_iio_dev(dev));
-
-       return sprintf(buf, "%d\n", st->resolution);
-}
-
-static ssize_t ad2s1210_store_resolution(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 char data;
-       unsigned char udata;
-       int ret;
-
-       ret = kstrtou8(buf, 10, &udata);
-       if (ret || udata < 10 || udata > 16) {
-               dev_err(dev, "ad2s1210: resolution out of range\n");
-               return -EINVAL;
-       }
-
-       data = (udata - 10) >> 1;
-
-       mutex_lock(&st->lock);
-       ret = regmap_update_bits(st->regmap, AD2S1210_REG_CONTROL,
-                                AD2S1210_SET_RES, data);
-       if (ret < 0)
-               goto error_ret;
-
-       ret = ad2s1210_set_resolution_gpios(st, udata);
-       if (ret < 0)
-               goto error_ret;
-
-       st->resolution = udata;
-       st->hysteresis_available[1] = 1 << (16 - st->resolution);
-       ret = len;
-
-error_ret:
-       mutex_unlock(&st->lock);
-       return ret;
-}
-
 /* read the fault register since last sample */
 static ssize_t ad2s1210_show_fault(struct device *dev,
                                   struct device_attribute *attr, char *buf)
@@ -413,7 +362,7 @@ static int ad2s1210_get_hysteresis(struct ad2s1210_state *st, int *val)
        if (ret < 0)
                return ret;
 
-       *val = ret << (16 - st->resolution);
+       *val = ret << (2 * (AD2S1210_RES_16 - st->resolution));
        return IIO_VAL_INT;
 }
 
@@ -577,8 +526,6 @@ static int ad2s1210_write_raw(struct iio_dev *indio_dev,
        }
 }
 
-static IIO_DEVICE_ATTR(bits, 0644,
-                      ad2s1210_show_resolution, ad2s1210_store_resolution, 0);
 static IIO_DEVICE_ATTR(fault, 0644,
                       ad2s1210_show_fault, ad2s1210_clear_fault, 0);
 
@@ -633,7 +580,6 @@ static const struct iio_chan_spec ad2s1210_channels[] = {
 };
 
 static struct attribute *ad2s1210_attributes[] = {
-       &iio_dev_attr_bits.dev_attr.attr,
        &iio_dev_attr_fault.dev_attr.attr,
        &iio_dev_attr_los_thrd.dev_attr.attr,
        &iio_dev_attr_dos_ovr_thrd.dev_attr.attr,
@@ -655,15 +601,12 @@ static int ad2s1210_initial(struct ad2s1210_state *st)
        int ret;
 
        mutex_lock(&st->lock);
-       ret = ad2s1210_set_resolution_gpios(st, st->resolution);
-       if (ret < 0)
-               goto error_ret;
 
        /* Use default config register value plus resolution from devicetree. */
        data = FIELD_PREP(AD2S1210_PHASE_LOCK_RANGE_44, 1);
        data |= FIELD_PREP(AD2S1210_ENABLE_HYSTERESIS, 1);
        data |= FIELD_PREP(AD2S1210_SET_ENRES, 0x3);
-       data |= FIELD_PREP(AD2S1210_SET_RES, (st->resolution - 10) >> 1);
+       data |= FIELD_PREP(AD2S1210_SET_RES, st->resolution);
 
        ret = regmap_write(st->regmap, AD2S1210_REG_CONTROL, data);
        if (ret < 0)
@@ -703,6 +646,35 @@ static const struct iio_info ad2s1210_info = {
        .debugfs_reg_access = &ad2s1210_debugfs_reg_access,
 };
 
+static int ad2s1210_setup_properties(struct ad2s1210_state *st)
+{
+       struct device *dev = &st->sdev->dev;
+       u32 val;
+       int ret;
+
+       ret = device_property_read_u32(dev, "assigned-resolution-bits", &val);
+       if (ret < 0)
+               return dev_err_probe(dev, ret,
+                       "failed to read assigned-resolution-bits property\n");
+
+       if (val < 10 || val > 16)
+               return dev_err_probe(dev, -EINVAL,
+                                    "resolution out of range: %u\n", val);
+
+       st->resolution = (val - 10) >> 1;
+       /*
+        * These are values that correlate to the hysteresis bit in the Control
+        * register. 0 = disabled, 1 = enabled. When enabled, the actual
+        * hysteresis is +/- 1 LSB of the raw position value. Which bit is the
+        * LSB depends on the specified resolution.
+        */
+       st->hysteresis_available[0] = 0;
+       st->hysteresis_available[1] = 1 << (2 * (AD2S1210_RES_16 -
+                                                st->resolution));
+
+       return 0;
+}
+
 static int ad2s1210_setup_clocks(struct ad2s1210_state *st)
 {
        struct device *dev = &st->sdev->dev;
@@ -724,6 +696,9 @@ static int ad2s1210_setup_clocks(struct ad2s1210_state *st)
 static int ad2s1210_setup_gpios(struct ad2s1210_state *st)
 {
        struct device *dev = &st->sdev->dev;
+       struct gpio_descs *resolution_gpios;
+       DECLARE_BITMAP(bitmap, 2);
+       int ret;
 
        /* should not be sampling on startup */
        st->sample_gpio = devm_gpiod_get(dev, "sample", GPIOD_OUT_LOW);
@@ -741,16 +716,32 @@ static int ad2s1210_setup_gpios(struct ad2s1210_state *st)
                return dev_err_probe(dev, -EINVAL,
                                     "requires exactly 2 mode-gpios\n");
 
-       /* both pins high means that we start with 16-bit resolution */
-       st->resolution_gpios = devm_gpiod_get_array(dev, "resolution",
-                                                   GPIOD_OUT_HIGH);
-       if (IS_ERR(st->resolution_gpios))
-               return dev_err_probe(dev, PTR_ERR(st->resolution_gpios),
+       /*
+        * If resolution gpios are provided, they get set to the required
+        * resolution, otherwise it is assumed the RES0 and RES1 pins are
+        * hard-wired to match the resolution indicated in the devicetree.
+        */
+       resolution_gpios = devm_gpiod_get_array_optional(dev, "resolution",
+                                                        GPIOD_ASIS);
+       if (IS_ERR(resolution_gpios))
+               return dev_err_probe(dev, PTR_ERR(resolution_gpios),
                                     "failed to request resolution GPIOs\n");
 
-       if (st->resolution_gpios->ndescs != 2)
-               return dev_err_probe(dev, -EINVAL,
-                                    "requires exactly 2 resolution-gpios\n");
+       if (resolution_gpios) {
+               if (resolution_gpios->ndescs != 2)
+                       return dev_err_probe(dev, -EINVAL,
+                                     "requires exactly 2 resolution-gpios\n");
+
+               bitmap[0] = st->resolution;
+
+               ret = gpiod_set_array_value(resolution_gpios->ndescs,
+                                           resolution_gpios->desc,
+                                           resolution_gpios->info,
+                                           bitmap);
+               if (ret < 0)
+                       return dev_err_probe(dev, ret,
+                                            "failed to set resolution gpios\n");
+       }
 
        return 0;
 }
@@ -814,9 +805,10 @@ static int ad2s1210_probe(struct spi_device *spi)
 
        mutex_init(&st->lock);
        st->sdev = spi;
-       st->resolution = 12;
-       st->hysteresis_available[0] = 0;
-       st->hysteresis_available[1] = 1 << (16 - st->resolution);
+
+       ret = ad2s1210_setup_properties(st);
+       if (ret < 0)
+               return ret;
 
        ret = ad2s1210_setup_clocks(st);
        if (ret < 0)