iio: filter: admv8818: Support frequencies >= 2^32

[ Upstream commit 9016776f1301627de78a633bda7c898425a56572 ]

This patch allows writing u64 values to the ADMV8818's high and low-pass
filter frequencies. It includes the following changes:

- Rejects negative frequencies in admv8818_write_raw.
- Adds a write_raw_get_fmt function to admv8818's iio_info, returning
  IIO_VAL_INT_64 for the high and low-pass filter 3dB frequency channels.

Fixes: f34fe888ad ("iio:filter:admv8818: add support for ADMV8818")
Signed-off-by: Brian Pellegrino <bpellegrino@arka.org>
Signed-off-by: Sam Winchenbach <swinchenbach@arka.org>
Link: https://patch.msgid.link/20250328174831.227202-7-sam.winchenbach@framepointer.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/iio/filter/admv8818.c

@@ -402,6 +402,19 @@ static int admv8818_read_lpf_freq(struct admv8818_state *st, u64 *lpf_freq)
 	return ret;
 }
 
+static int admv8818_write_raw_get_fmt(struct iio_dev *indio_dev,
+								struct iio_chan_spec const *chan,
+								long mask)
+{
+	switch (mask) {
+	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
+	case IIO_CHAN_INFO_HIGH_PASS_FILTER_3DB_FREQUENCY:
+		return IIO_VAL_INT_64;
+	default:
+		return -EINVAL;
+	}
+}
+
 static int admv8818_write_raw(struct iio_dev *indio_dev,
 			      struct iio_chan_spec const *chan,
 			      int val, int val2, long info)
@@ -410,6 +423,9 @@ static int admv8818_write_raw(struct iio_dev *indio_dev,
 
 	u64 freq = ((u64)val2 << 32 | (u32)val);
 
+	if ((s64)freq < 0)
+		return -EINVAL;
+
 	switch (info) {
 	case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
 		return admv8818_lpf_select(st, freq);
@@ -571,6 +587,7 @@ set_mode:
 
 static const struct iio_info admv8818_info = {
 	.write_raw = admv8818_write_raw,
+	.write_raw_get_fmt = admv8818_write_raw_get_fmt,
 	.read_raw = admv8818_read_raw,
 	.debugfs_reg_access = &admv8818_reg_access,
 };