[PATCH v5 09/14] iio: adc: ad7768-1: Add GPIO controller support

[Jonathan Santos <Jonathan.Santos@analog.com>]

From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>

The AD7768-1 has the ability to control other local hardware (such as gain
stages),to power down other blocks in the signal chain, or read local
status signals over the SPI interface.

Add direct mode conditional locks in the gpio callbacks to prevent register
access when the device is in buffered mode.

This change exports the AD7768-1's four gpios and makes them accessible
at an upper layer.

Reviewed-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Co-developed-by: Jonathan Santos <Jonathan.Santos@analog.com>
Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
---
v5 Changes:
* Use the new new iio_device_claim/release_direct() functions.
* replaced gpiochip_add_data() for devm_gpiochip_add_data().

v4 Changes:
* Mentioned in the commit message that we cannot tweak the GPIO controller
  when the device is not in direct mode.

v3 Changes:
* Fixed SoB order.
* Added mising iio_device_release_direct_mode().
* Simplified some regmap writes.
* Removed ad7768_gpio_request() callback.
* Fixed line wrapping.

v2 Changes:
* Replaced mutex for iio_device_claim_direct_mode().
* Use gpio-controller property to conditionally enable the
  GPIO support.
* OBS: when the GPIO is configured as output, we should read 
  the current state value from AD7768_REG_GPIO_WRITE.
---
 drivers/iio/adc/ad7768-1.c | 139 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 137 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
index 13d17a13b6ea..11e5456f50d3 100644
--- a/drivers/iio/adc/ad7768-1.c
+++ b/drivers/iio/adc/ad7768-1.c
@@ -9,6 +9,8 @@
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/err.h>
+#include <linux/gpio.h>
+#include <linux/gpio/driver.h>
 #include <linux/gpio/consumer.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -86,6 +88,16 @@
 #define AD7768_REG_ANALOG2_VCM_MSK	GENMASK(2, 0)
 #define AD7768_REG_ANALOG2_VCM(x)	FIELD_PREP(AD7768_REG_ANALOG2_VCM_MSK, (x))
 
+/* AD7768_REG_GPIO_CONTROL */
+#define AD7768_GPIO_UNIVERSAL_EN	BIT(7)
+#define AD7768_GPIO_CONTROL_MSK		GENMASK(3, 0)
+
+/* AD7768_REG_GPIO_WRITE */
+#define AD7768_GPIO_WRITE_MSK		GENMASK(3, 0)
+
+/* AD7768_REG_GPIO_READ */
+#define AD7768_GPIO_READ_MSK		GENMASK(3, 0)
+
 #define AD7768_VCM_OFF			0x07
 
 enum ad7768_conv_mode {
@@ -168,6 +180,7 @@ struct ad7768_state {
 	struct regulator_dev *vcm_rdev;
 	unsigned int vcm_output_sel;
 	struct clk *mclk;
+	struct gpio_chip gpiochip;
 	unsigned int mclk_freq;
 	unsigned int samp_freq;
 	struct completion completion;
@@ -353,6 +366,120 @@ static int ad7768_set_dig_fil(struct ad7768_state *st,
 	return 0;
 }
 
+static int ad7768_gpio_direction_input(struct gpio_chip *chip, unsigned int offset)
+{
+	struct iio_dev *indio_dev = gpiochip_get_data(chip);
+	struct ad7768_state *st = iio_priv(indio_dev);
+	int ret;
+
+	if (!iio_device_claim_direct(indio_dev))
+		return -EBUSY;
+
+	ret = regmap_clear_bits(st->regmap, AD7768_REG_GPIO_CONTROL,
+				BIT(offset));
+	iio_device_release_direct(indio_dev);
+
+	return ret;
+}
+
+static int ad7768_gpio_direction_output(struct gpio_chip *chip,
+					unsigned int offset, int value)
+{
+	struct iio_dev *indio_dev = gpiochip_get_data(chip);
+	struct ad7768_state *st = iio_priv(indio_dev);
+	int ret;
+
+	if (!iio_device_claim_direct(indio_dev))
+		return -EBUSY;
+
+	ret = regmap_set_bits(st->regmap, AD7768_REG_GPIO_CONTROL,
+			      BIT(offset));
+	iio_device_release_direct(indio_dev);
+
+	return ret;
+}
+
+static int ad7768_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct iio_dev *indio_dev = gpiochip_get_data(chip);
+	struct ad7768_state *st = iio_priv(indio_dev);
+	unsigned int val;
+	int ret;
+
+	if (!iio_device_claim_direct(indio_dev))
+		return -EBUSY;
+
+	ret = regmap_read(st->regmap, AD7768_REG_GPIO_CONTROL, &val);
+	if (ret)
+		goto err_release;
+
+	/*
+	 * If the GPIO is configured as an output, read the current value from
+	 * AD7768_REG_GPIO_WRITE. Otherwise, read the input value from
+	 * AD7768_REG_GPIO_READ.
+	 */
+	if (val & BIT(offset))
+		ret = regmap_read(st->regmap, AD7768_REG_GPIO_WRITE, &val);
+	else
+		ret = regmap_read(st->regmap, AD7768_REG_GPIO_READ, &val);
+	if (ret)
+		goto err_release;
+
+	ret = !!(val & BIT(offset));
+err_release:
+	iio_device_release_direct(indio_dev);
+
+	return ret;
+}
+
+static void ad7768_gpio_set(struct gpio_chip *chip, unsigned int offset, int value)
+{
+	struct iio_dev *indio_dev = gpiochip_get_data(chip);
+	struct ad7768_state *st = iio_priv(indio_dev);
+	unsigned int val;
+	int ret;
+
+	if (!iio_device_claim_direct(indio_dev))
+		return;
+
+	ret = regmap_read(st->regmap, AD7768_REG_GPIO_CONTROL, &val);
+	if (ret)
+		goto err_release;
+
+	if (val & BIT(offset))
+		regmap_update_bits(st->regmap, AD7768_REG_GPIO_WRITE,
+				   BIT(offset), value << offset);
+
+err_release:
+	iio_device_release_direct(indio_dev);
+}
+
+static int ad7768_gpio_init(struct iio_dev *indio_dev)
+{
+	struct ad7768_state *st = iio_priv(indio_dev);
+	int ret;
+
+	ret = regmap_write(st->regmap, AD7768_REG_GPIO_CONTROL,
+			   AD7768_GPIO_UNIVERSAL_EN);
+	if (ret)
+		return ret;
+
+	st->gpiochip = (struct gpio_chip) {
+		.label = "ad7768_1_gpios",
+		.base = -1,
+		.ngpio = 4,
+		.parent = &st->spi->dev,
+		.can_sleep = true,
+		.direction_input = ad7768_gpio_direction_input,
+		.direction_output = ad7768_gpio_direction_output,
+		.get = ad7768_gpio_get,
+		.set = ad7768_gpio_set,
+		.owner = THIS_MODULE,
+	};
+
+	return devm_gpiochip_add_data(&st->spi->dev, &st->gpiochip, indio_dev);
+}
+
 static int ad7768_set_freq(struct ad7768_state *st,
 			   unsigned int freq)
 {
@@ -494,8 +621,9 @@ static const struct iio_info ad7768_info = {
 	.debugfs_reg_access = &ad7768_reg_access,
 };
 
-static int ad7768_setup(struct ad7768_state *st)
+static int ad7768_setup(struct iio_dev *indio_dev)
 {
+	struct ad7768_state *st = iio_priv(indio_dev);
 	int ret;
 
 	st->gpio_reset = devm_gpiod_get_optional(&st->spi->dev, "reset",
@@ -528,6 +656,13 @@ static int ad7768_setup(struct ad7768_state *st)
 	if (IS_ERR(st->gpio_sync_in))
 		return PTR_ERR(st->gpio_sync_in);
 
+	/* Only create a Chip GPIO if flagged for it */
+	if (device_property_read_bool(&st->spi->dev, "gpio-controller")) {
+		ret = ad7768_gpio_init(indio_dev);
+		if (ret < 0)
+			return ret;
+	}
+
 	/* Set the default sampling frequency to 32000 kSPS */
 	return ad7768_set_freq(st, 32000);
 }
@@ -884,7 +1019,7 @@ static int ad7768_probe(struct spi_device *spi)
 	if (ret)
 		return ret;
 
-	ret = ad7768_setup(st);
+	ret = ad7768_setup(indio_dev);
 	if (ret < 0) {
 		dev_err(&spi->dev, "AD7768 setup failed\n");
 		return ret;
-- 
2.34.1