lkml.org 
[lkml]   [2018]   [Jun]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v2 1/2] iio: dac: Add AD5758 support
On Thu, Jun 7, 2018 at 4:09 PM, Stefan Popa <stefan.popa@analog.com> wrote:
> The AD5758 is a single channel DAC with 16-bit precision which uses the SPI
> interface that operates at clock rates up to 50MHz.
>
> The output can be configured as voltage or current and is available on a
> single terminal.
>
> Datasheet:
> http://www.analog.com/media/en/technical-documentation/data-sheets/ad5758.pdf

> +#include <linux/fs.h>
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/sysfs.h>
> +#include <linux/spi/spi.h>
> +#include <linux/delay.h>

Can you keep the list in order?

> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/property.h>

Same, and property.h more generic if you wish than iio.

> +/* AD5758_DIGITAL_DIAG_RESULTS */
> +#define AD5758_DIG_DIAG_RES_CAL_MEM_UNREFRESHED_MSK BIT(15)

This name way too long.
Also, check the rest near to this length and try to shorten them.

> +#define AD5758_REG_WRITE(x) (0x80 | ((x) & 0x1F))

Name of macro is misleading. It rather some value preparations than "write".

> +/* x^8 + x^2 + x^1 + x^0 */
> +#define AD5758_CRC8_POLY 0x07

Where is it used?

> +enum ad5758_output_range {
> + AD5758_RANGE_0V_5V,
> + AD5758_RANGE_0V_10V,
> + AD5758_RANGE_PLUSMINUS_5V,
> + AD5758_RANGE_PLUSMINUS_10V,
> + AD5758_RANGE_0mA_20mA = 8,

Hmm... why it starts from 8? Perhaps some explanation on top of enum?

> + AD5758_RANGE_0mA_24mA,
> + AD5758_RANGE_4mA_24mA,
> + AD5758_RANGE_PLUSMINUS_20mA,
> + AD5758_RANGE_PLUSMINUS_24mA,
> + AD5758_RANGE_MINUS_1mA_PLUS_22mA,
> +};

> +static int ad5758_get_array_index(const int *array, unsigned int size, int val)
> +{
> + int i;
> +
> + for (i = 0; i < size; i++) {
> + if (val == array[i])
> + return i;
> + }
> +
> + return -EINVAL;
> +}

bsearch? (lib/bsearch.c)

> +static int ad5758_wait_for_task_complete(struct ad5758_state *st,
> + unsigned int reg,
> + unsigned int mask)
> +{
> + unsigned int timeout;
> + int ret;
> +
> + timeout = 4;
> + do {
> + ret = ad5758_spi_reg_read(st, reg);
> + if (ret < 0)
> + return ret;
> +
> + if (!(ret & mask))
> + return 0;
> +

> + mdelay(1);

No way. CPU would be busy for 1ms at least!

> + } while (--timeout);
> +
> + dev_err(&st->spi->dev,
> + "Error reading bit 0x%x in 0x%x register\n", mask, reg);
> +
> + return -EIO;
> +}

> +static int ad5758_soft_reset(struct ad5758_state *st)
> +{
> + int ret;
> +
> + ret = ad5758_spi_reg_write(st, AD5758_KEY, AD5758_KEY_CODE_RESET_1);
> + if (ret < 0)
> + return ret;
> +
> + ret = ad5758_spi_reg_write(st, AD5758_KEY, AD5758_KEY_CODE_RESET_2);
> +

> + mdelay(1);

Explanation must be given for such a long delay without idling.

> +
> + return ret;
> +}

> + if (readval == NULL) {

Why not positive check?

if (readval) {
...
} else {
...
}

> + ret = ad5758_spi_reg_write(st, reg, writeval);
> + } else {
> + ret = ad5758_spi_reg_read(st, reg);
> + if (ret < 0) {
> + mutex_unlock(&st->lock);
> + return ret;
> + }
> +
> + *readval = ret;
> + ret = 0;
> + }

> + ret = strtobool(buf, &pwr_down);
> + if (ret)
> + return ret;

kstrtobool(), please.

> +static const struct iio_chan_spec_ext_info ad5758_ext_info[] = {
> + {
> + .name = "powerdown",
> + .read = ad5758_read_powerdown,
> + .write = ad5758_write_powerdown,
> + .shared = IIO_SEPARATE,
> + },
> + { },

Terminator is better without comma.

> +};

> + st->data[0].d32 =

> + cpu_to_be32(
> + (AD5758_REG_WRITE(AD5758_DIGITAL_DIAG_CONFIG) << 24) | 0x5C3A);

Either do this one line, or introduce a temporary variable for
parameter of cpu_to_be32().

> + if (!device_property_read_u32(&st->spi->dev, "adi,range", &tmp)) {

Would be better to have
ret = device_property_...();
if (ret) {
...
} else {
...
}

if it's optional and

if (ret) {
...
return -ERRNO; // goto cleanup; etc
}

> + for (i = 0; i < ARRAY_SIZE(ad5758_min_max_table); i++) {
> + if (tmp == ad5758_min_max_table[i].reg) {
> + st->out_range = i;
> + break;
> + }
> + }
> +
> + if (i == ARRAY_SIZE(ad5758_min_max_table))
> + dev_warn(&st->spi->dev,
> + "range invalid, using 0V to 5V\n");
> + } else {
> + dev_dbg(&st->spi->dev,
> + "Missing \"range\" property, using 0V to 5V\n");
> + }

> + if (!device_property_read_u32_array(&st->spi->dev, "adi,slew",
> + tmparray, 3)) {

...

> + } else {
> + dev_dbg(&st->spi->dev,
> + "Missing \"slew\" property, using 16kHz and 4 LSB\n");
> + }

Ditto.

> + ad5758_parse_dt(st);

No errors? Nothing fatal?

--
With Best Regards,
Andy Shevchenko

\
 
 \ /
  Last update: 2018-06-12 18:28    [W:0.063 / U:5.364 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site