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

William Breathitt Gray
2022-06-14T16:12:39Z

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On Tue, Jun 14, 2022 at 12:22:48PM +0100, Jonathan Cameron wrote:
> On Mon, 6 Jun 2022 10:15:17 -0400
> William Breathitt Gray <william.gray@linaro.org> wrote:
>
> > Reduce magic numbers and improve code readability by implementing and
> > utilizing named register data structures.
> >
> > Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
>
> 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.

This address doubles as the 8-bit Software Strobe Register; writing an
8-bit value to this address will initiate an ADC sample capture. I'll
rename this member to ssr_ad and add some comments to make this more
explicit.

>
> > + 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];

Ack.

William Breathitt Gray

> >
> > 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);
>

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