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From:   David Lechner <dlechner@baylibre.com>
To:     linux-iio@vger.kernel.org, devicetree@vger.kernel.org,
        linux-staging@lists.linux.dev
Cc:     linux-kernel@vger.kernel.org, Jonathan Cameron <jic23@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Michael Hennerich <Michael.Hennerich@analog.com>,
        =?UTF-8?q?Nuno=20S=C3=A1?= <nuno.sa@analog.com>,
        Axel Haslam <ahaslam@baylibre.com>,
        Philip Molloy <pmolloy@baylibre.com>,
        David Lechner <dlechner@baylibre.com>
Subject: [v2 13/19] staging: iio: resolver: ad2s1210: implement hysteresis as channel attr
Date:   Thu, 21 Sep 2023 09:19:41 -0500
Message-Id: <20230921141947.57784-16-dlechner@baylibre.com>
In-Reply-To: <20230921141947.57784-1-dlechner@baylibre.com>
References: <20230921141947.57784-1-dlechner@baylibre.com>
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The AD2S1210 resolver has a hysteresis feature that can be used to
prevent flicker in the LSB of the position register. This can be either
enabled or disabled. Disabling hysteresis is useful for increasing
precision by oversampling.

Signed-off-by: David Lechner <dlechner@baylibre.com>
---
 drivers/staging/iio/resolver/ad2s1210.c | 88 ++++++++++++++++++++++++-
 1 file changed, 85 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
index 7a1069d948eb..fe413759deb9 100644
--- a/drivers/staging/iio/resolver/ad2s1210.c
+++ b/drivers/staging/iio/resolver/ad2s1210.c
@@ -80,7 +80,6 @@ struct ad2s1210_state {
 	/** The external oscillator frequency in Hz. */
 	unsigned long fclkin;
 	unsigned int fexcit;
-	bool hysteresis;
 	u8 resolution;
 	u8 rx[2] __aligned(IIO_DMA_MINALIGN);
 	u8 tx[2];
@@ -456,6 +455,27 @@ static int ad2s1210_read_raw(struct iio_dev *indio_dev,
 		}
 		break;
 
+	case IIO_CHAN_INFO_HYSTERESIS:
+		switch (chan->type) {
+		case IIO_ANGL:
+			mutex_lock(&st->lock);
+			ret = regmap_test_bits(st->regmap, AD2S1210_REG_CONTROL,
+					       AD2S1210_ENABLE_HYSTERESIS);
+			if (ret < 0)
+				goto error_info_hysteresis;
+
+			*val = !!ret;
+			ret = IIO_VAL_INT;
+
+error_info_hysteresis:
+			mutex_unlock(&st->lock);
+			break;
+		default:
+			ret = -EINVAL;
+			break;
+		}
+		break;
+
 	default:
 		ret = -EINVAL;
 		break;
@@ -464,6 +484,64 @@ static int ad2s1210_read_raw(struct iio_dev *indio_dev,
 	return ret;
 }
 
+static int ad2s1210_read_avail(struct iio_dev *indio_dev,
+			       struct iio_chan_spec const *chan,
+			       const int **vals, int *type,
+			       int *length, long mask)
+{
+	static const int available[] = { 0, 1 };
+	int ret = -EINVAL;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_HYSTERESIS:
+		switch (chan->type) {
+		case IIO_ANGL:
+			*vals = available;
+			*type = IIO_VAL_INT;
+			*length = ARRAY_SIZE(available);
+			ret = IIO_AVAIL_LIST;
+			break;
+		default:
+			break;
+		}
+	default:
+		break;
+	}
+
+	return ret;
+}
+
+static int ad2s1210_write_raw(struct iio_dev *indio_dev,
+			      struct iio_chan_spec const *chan,
+			      int val, int val2, long mask)
+{
+	struct ad2s1210_state *st = iio_priv(indio_dev);
+	int ret = -EINVAL;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_HYSTERESIS:
+		switch (chan->type) {
+		case IIO_ANGL:
+			mutex_lock(&st->lock);
+			ret = regmap_update_bits(st->regmap, AD2S1210_REG_CONTROL,
+						 AD2S1210_ENABLE_HYSTERESIS,
+						 val ? AD2S1210_ENABLE_HYSTERESIS
+						     : 0);
+			mutex_unlock(&st->lock);
+			break;
+
+		default:
+			break;
+		}
+		break;
+
+	default:
+		break;
+	}
+
+	return ret;
+}
+
 static IIO_DEVICE_ATTR(fexcit, 0644,
 		       ad2s1210_show_fexcit,	ad2s1210_store_fexcit, 0);
 static IIO_DEVICE_ATTR(bits, 0644,
@@ -499,7 +577,10 @@ static const struct iio_chan_spec ad2s1210_channels[] = {
 		.indexed = 1,
 		.channel = 0,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
-				      BIT(IIO_CHAN_INFO_SCALE),
+				      BIT(IIO_CHAN_INFO_SCALE) |
+				      BIT(IIO_CHAN_INFO_HYSTERESIS),
+		.info_mask_separate_available =
+					BIT(IIO_CHAN_INFO_HYSTERESIS),
 	}, {
 		.type = IIO_ANGL_VEL,
 		.indexed = 1,
@@ -573,6 +654,8 @@ static int ad2s1210_debugfs_reg_access(struct iio_dev *indio_dev,
 
 static const struct iio_info ad2s1210_info = {
 	.read_raw = ad2s1210_read_raw,
+	.read_avail = ad2s1210_read_avail,
+	.write_raw = ad2s1210_write_raw,
 	.attrs = &ad2s1210_attribute_group,
 	.debugfs_reg_access = &ad2s1210_debugfs_reg_access,
 };
@@ -689,7 +772,6 @@ static int ad2s1210_probe(struct spi_device *spi)
 
 	mutex_init(&st->lock);
 	st->sdev = spi;
-	st->hysteresis = true;
 	st->resolution = 12;
 	st->fexcit = AD2S1210_DEF_EXCIT;
 
-- 
2.34.1