Re: [PATCH v2 12/16] iio: adc: ad7768-1: Add GPIO controller support

[Jonathan Santos <jonath4nns@gmail.com>]

On 01/27, David Lechner wrote:
> On 1/27/25 9:13 AM, Jonathan Santos wrote:
> > 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.
> > 
> > This change exports the AD7768-1's four gpios and makes them accessible
> > at an upper layer.
> > 
> > Co-developed-by: Jonathan Santos <Jonathan.Santos@analog.com>
> > Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
> > Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> > ---
> > 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 | 148 ++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 146 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
> > index c540583808c2..e3ea078e6ec4 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>
> > @@ -79,6 +81,19 @@
> >  #define AD7768_CONV_MODE_MSK		GENMASK(2, 0)
> >  #define AD7768_CONV_MODE(x)		FIELD_PREP(AD7768_CONV_MODE_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_GPIO_INPUT(x)		0x00
> > +#define AD7768_GPIO_OUTPUT(x)		BIT(x)
> > +
> >  #define AD7768_RD_FLAG_MSK(x)		(BIT(6) | ((x) & 0x3F))
> >  #define AD7768_WR_FLAG_MSK(x)		((x) & 0x3F)
> >  
> > @@ -160,6 +175,8 @@ struct ad7768_state {
> >  	struct regulator *vref;
> >  	struct mutex lock;
> >  	struct clk *mclk;
> > +	struct gpio_chip gpiochip;
> > +	unsigned int gpio_avail_map;
> >  	unsigned int mclk_freq;
> >  	unsigned int samp_freq;
> >  	struct completion completion;
> > @@ -309,6 +326,125 @@ 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;
> > +
> > +	ret = iio_device_claim_direct_mode(indio_dev);
> > +	if (ret)
> > +		return ret;
> 
> Missing iio_device_release_direct_mode() here and in other functions.
> 
> (And we are in the process of removing iio_device_claim_direct_scoped(), so
> don't use that.)
> 

Sure, my mistake. I am fixing this.

> > +
> > +	return regmap_update_bits(st->regmap,
> > +				  AD7768_REG_GPIO_CONTROL,
> > +				  BIT(offset),
> > +				  AD7768_GPIO_INPUT(offset));
> 
> Can be simplified to regmap_clear_bits(), then we can get rid of the odd
> AD7768_GPIO_INPUT macro that ignores the argument.
> 
> > +}
> > +
> > +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;
> > +
> > +	ret = iio_device_claim_direct_mode(indio_dev);
> > +	if (ret)
> > +		return ret;
> > +
> > +	return regmap_update_bits(st->regmap,
> > +				  AD7768_REG_GPIO_CONTROL,
> > +				  BIT(offset),
> > +				  AD7768_GPIO_OUTPUT(offset));
> 
> And regmap_set_bits() here.
> 
> > +}
> > +
> > +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;
> > +
> > +	ret = iio_device_claim_direct_mode(indio_dev);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = regmap_read(st->regmap, AD7768_REG_GPIO_CONTROL, &val);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	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);
> 
> Can we get a comment explaining why GPIO_READ doesn't work in output mode?
> 
> Or if it does work, we can simplify this function.
> 
> 

The datasheet does not mention this; I reached this conclusion through testing.
It seems they separate the output state from the read register. Anyway, I will
add a comment.

> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return !!(val & BIT(offset));
> > +}
> > +
> > +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;
> > +
> > +	ret = iio_device_claim_direct_mode(indio_dev);
> > +	if (ret)
> > +		return;
> > +
> > +	ret = regmap_read(st->regmap, AD7768_REG_GPIO_CONTROL, &val);
> > +	if (ret < 0)
> > +		return;
> > +
> > +	if (val & BIT(offset))
> > +		regmap_update_bits(st->regmap,
> > +				   AD7768_REG_GPIO_WRITE,
> > +				   BIT(offset),
> > +				   (value << offset));
> 
> Can remove extra ().
> 
> > +}
> > +
> > +static int ad7768_gpio_request(struct gpio_chip *chip, unsigned int offset)
> > +{
> > +	struct iio_dev *indio_dev = gpiochip_get_data(chip);
> > +	struct ad7768_state *st = iio_priv(indio_dev);
> > +
> > +	if (!(st->gpio_avail_map & BIT(offset)))
> > +		return -ENODEV;
> > +
> > +	st->gpio_avail_map &= ~BIT(offset);
> 
> Is this really needed? It seems like GPIO core would be keeping track already.
> 
> Also would need a .free callback to undo this action.
> 
> It seems like most ADC's with GPIO controllers don't implement .request though.
> 

Indeed, .request is optional and does not seem to make a pratical  
difference if the core handles that. If that is the case i can remove
this

> > +
> > +	return 0;
> > +}
> > +