Re: [PATCH 1/2] iio: adc: stx104: Implement and utilize register structures

From: Jonathan Cameron
Date: Tue Jun 14 2022 - 07:14:01 EST

On Mon, 6 Jun 2022 10:15:17 -0400
William Breathitt Gray <william.gray@xxxxxxxxxx> wrote:

> Reduce magic numbers and improve code readability by implementing and
> utilizing named register data structures.
>
> Signed-off-by: William Breathitt Gray <william.gray@xxxxxxxxxx>

A few comments inline, but looks fine to me otherwise.

Jonathan

> ---
> drivers/iio/adc/stx104.c | 70 +++++++++++++++++++++++++++-------------
> 1 file changed, 47 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/iio/adc/stx104.c b/drivers/iio/adc/stx104.c
> index 7552351bfed9..7656b363e281 100644
> --- a/drivers/iio/adc/stx104.c
> +++ b/drivers/iio/adc/stx104.c
> @@ -16,6 +16,7 @@
> #include <linux/module.h>
> #include <linux/moduleparam.h>
> #include <linux/spinlock.h>
> +#include <linux/types.h>
>
> #define STX104_OUT_CHAN(chan) { \
> .type = IIO_VOLTAGE, \
> @@ -44,14 +45,36 @@ static unsigned int num_stx104;
> module_param_hw_array(base, uint, ioport, &num_stx104, 0);
> MODULE_PARM_DESC(base, "Apex Embedded Systems STX104 base addresses");
>
> +/**
> + * struct stx104_reg - device register structure
> + * @ad: ADC Data
> + * @achan: ADC Channel
> + * @dio: Digital I/O
> + * @dac: DAC Channels
> + * @cir_asr: Clear Interrupts and ADC Status
> + * @acr: ADC Control
> + * @pccr_fsh: Pacer Clock Control and FIFO Status MSB
> + * @acfg: ADC Configuration
> + */
> +struct stx104_reg {
> + u16 ad;
> + u8 achan;
> + u8 dio;
> + u16 dac[2];
> + u8 cir_asr;
> + u8 acr;
> + u8 pccr_fsh;
> + u8 acfg;
> +};
> +
> /**
> * struct stx104_iio - IIO device private data structure
> * @chan_out_states: channels' output states
> - * @base: base port address of the IIO device
> + * @reg: I/O address offset for the device registers
> */
> struct stx104_iio {
> unsigned int chan_out_states[STX104_NUM_OUT_CHAN];
> - void __iomem *base;
> + struct stx104_reg __iomem *reg;
> };
>
> /**
> @@ -64,7 +87,7 @@ struct stx104_iio {
> struct stx104_gpio {
> struct gpio_chip chip;
> spinlock_t lock;
> - void __iomem *base;
> + u8 __iomem *base;
> unsigned int out_state;
> };
>
> @@ -72,6 +95,7 @@ static int stx104_read_raw(struct iio_dev *indio_dev,
> struct iio_chan_spec const *chan, int *val, int *val2, long mask)
> {
> struct stx104_iio *const priv = iio_priv(indio_dev);
> + struct stx104_reg __iomem *const reg = priv->reg;
> unsigned int adc_config;
> int adbu;
> int gain;
> @@ -79,7 +103,7 @@ static int stx104_read_raw(struct iio_dev *indio_dev,
> switch (mask) {
> case IIO_CHAN_INFO_HARDWAREGAIN:
> /* get gain configuration */
> - adc_config = ioread8(priv->base + 11);
> + adc_config = ioread8(&reg->acfg);
> gain = adc_config & 0x3;
>
> *val = 1 << gain;
> @@ -91,24 +115,24 @@ static int stx104_read_raw(struct iio_dev *indio_dev,
> }
>
> /* select ADC channel */
> - iowrite8(chan->channel | (chan->channel << 4), priv->base + 2);
> + iowrite8(chan->channel | (chan->channel << 4), &reg->achan);
>
> /* trigger ADC sample capture and wait for completion */
> - iowrite8(0, priv->base);
> - while (ioread8(priv->base + 8) & BIT(7));
> + iowrite8(0, &reg->ad);

Curious - 8 bit write to a 16 bit address? Maybe worth a comment
on why.

> + while (ioread8(&reg->cir_asr) & BIT(7));
>
> - *val = ioread16(priv->base);
> + *val = ioread16(&reg->ad);
> return IIO_VAL_INT;
> case IIO_CHAN_INFO_OFFSET:
> /* get ADC bipolar/unipolar configuration */
> - adc_config = ioread8(priv->base + 11);
> + adc_config = ioread8(&reg->acfg);
> adbu = !(adc_config & BIT(2));
>
> *val = -32768 * adbu;
> return IIO_VAL_INT;
> case IIO_CHAN_INFO_SCALE:
> /* get ADC bipolar/unipolar and gain configuration */
> - adc_config = ioread8(priv->base + 11);
> + adc_config = ioread8(&reg->acfg);
> adbu = !(adc_config & BIT(2));
> gain = adc_config & 0x3;
>
> @@ -130,16 +154,16 @@ static int stx104_write_raw(struct iio_dev *indio_dev,
> /* Only four gain states (x1, x2, x4, x8) */
> switch (val) {
> case 1:
> - iowrite8(0, priv->base + 11);
> + iowrite8(0, &priv->reg->acfg);
> break;
> case 2:
> - iowrite8(1, priv->base + 11);
> + iowrite8(1, &priv->reg->acfg);
> break;
> case 4:
> - iowrite8(2, priv->base + 11);
> + iowrite8(2, &priv->reg->acfg);
> break;
> case 8:
> - iowrite8(3, priv->base + 11);
> + iowrite8(3, &priv->reg->acfg);
> break;
> default:
> return -EINVAL;
> @@ -153,7 +177,7 @@ static int stx104_write_raw(struct iio_dev *indio_dev,
> return -EINVAL;
>
> priv->chan_out_states[chan->channel] = val;
> - iowrite16(val, priv->base + 4 + 2 * chan->channel);
> + iowrite16(val, priv->reg->dac + chan->channel);
Perhaps for consistency with below go with
&priv->reg->dac[chan->channels];

>
> return 0;
> }
> @@ -307,15 +331,15 @@ static int stx104_probe(struct device *dev, unsigned int id)
> }
>
> priv = iio_priv(indio_dev);
> - priv->base = devm_ioport_map(dev, base[id], STX104_EXTENT);
> - if (!priv->base)
> + priv->reg = devm_ioport_map(dev, base[id], STX104_EXTENT);
> + if (!priv->reg)
> return -ENOMEM;
>
> indio_dev->info = &stx104_info;
> indio_dev->modes = INDIO_DIRECT_MODE;
>
> /* determine if differential inputs */
> - if (ioread8(priv->base + 8) & BIT(5)) {
> + if (ioread8(&priv->reg->cir_asr) & BIT(5)) {
> indio_dev->num_channels = ARRAY_SIZE(stx104_channels_diff);
> indio_dev->channels = stx104_channels_diff;
> } else {
> @@ -326,14 +350,14 @@ static int stx104_probe(struct device *dev, unsigned int id)
> indio_dev->name = dev_name(dev);
>
> /* configure device for software trigger operation */
> - iowrite8(0, priv->base + 9);
> + iowrite8(0, &priv->reg->acr);
>
> /* initialize gain setting to x1 */
> - iowrite8(0, priv->base + 11);
> + iowrite8(0, &priv->reg->acfg);
>
> /* initialize DAC output to 0V */
> - iowrite16(0, priv->base + 4);
> - iowrite16(0, priv->base + 6);
> + iowrite16(0, &priv->reg->dac[0]);
> + iowrite16(0, &priv->reg->dac[1]);
>
> stx104gpio->chip.label = dev_name(dev);
> stx104gpio->chip.parent = dev;
> @@ -348,7 +372,7 @@ static int stx104_probe(struct device *dev, unsigned int id)
> stx104gpio->chip.get_multiple = stx104_gpio_get_multiple;
> stx104gpio->chip.set = stx104_gpio_set;
> stx104gpio->chip.set_multiple = stx104_gpio_set_multiple;
> - stx104gpio->base = priv->base + 3;
> + stx104gpio->base = &priv->reg->dio;
> stx104gpio->out_state = 0x0;
>
> spin_lock_init(&stx104gpio->lock);