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Date: Sat, 17 Apr 2021 15:39:12 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Tomas Melin <tomas.melin@...sala.com>
Cc: Jonathan Cameron <jic23@...nel.org>,
devicetree <devicetree@...r.kernel.org>,
linux-iio <linux-iio@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] iio: accel: Add driver for Murata SCA3300 accelerometer
On Fri, Apr 16, 2021 at 5:21 PM Tomas Melin <tomas.melin@...sala.com> wrote:
>
> Add initial support for Murata SCA3300 3-axis industrial
> accelerometer with digital SPI interface. This device also
> provides a temperature measurement.
>
> Device product page including datasheet can be found at:
> https://www.murata.com/en-global/products/sensor/accel/sca3300
Can you create a tag out of it, i.e.
Datasheet: <URL>
?
> Signed-off-by: Tomas Melin <tomas.melin@...sala.com>
...
> obj-$(CONFIG_SCA3000) += sca3000.o
> +obj-$(CONFIG_SCA3300) += sca3300.o
How much difference between them?
...
> +/*
> + * Copyright (c) 2021 Vaisala Oyj. All rights reserved.
> + */
One line
> +#include <asm/unaligned.h>
Usually asm/* goes after linux/*
> +#include <linux/bitops.h>
> +#include <linux/crc8.h>
> +#include <linux/delay.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
Can you move this below...
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
...here.
So, you will have something like this at the end:
linux/*
asm/*
linux/iio*
...
> +#define SCA3300_REG_STATUS 0x6
> +#define SCA3300_REG_MODE 0xd
> +#define SCA3300_REG_WHOAMI 0x10
> +#define SCA3300_VALUE_SW_RESET 0x20
> +#define SCA3300_CRC8_POLYNOMIAL 0x1d
> +#define SCA3300_DEVICE_ID 0x51
> +#define SCA3300_RS_ERROR 0x3
> +#define SCA3300_SELBANK 0x1f
Is it mask or value or offset?
> +#define SCA3300_STATUS_MASK 0x1ff
GENMASK()
TAB indentation to all?
This all like an unordered pile of something. I can't guess the value
for which register and so on. Can you put an order here?
...
> +#define SCA3300_ACCEL_CHANNEL(index, reg, axis) { \
> + }
Something wrong with indentation here.
...
> +static const int sca3300_accel_scale[][2] = {{0, 370}, {0, 741}, {0, 185},
> + {0, 185}};
Put it all on one line.
...
> +static const unsigned long sca3300_scan_masks[] = {
> + BIT(SCA3300_ACC_X) | BIT(SCA3300_ACC_Y) | BIT(SCA3300_ACC_Z) |
> + BIT(SCA3300_TEMP),
> + 0};
Something wrong with indentation, i.e. }; should be on the following line.
...
> +static int sca3300_transfer(struct sca3300_data *sca_data, int *val)
> +{
> + struct spi_delay delay = {.value = 10, .unit = SPI_DELAY_UNIT_USECS};
> + int32_t ret;
> + int rs;
> + u8 crc;
> + struct spi_transfer xfers[2] = {
> + {
> + .tx_buf = sca_data->txbuf,
> + .rx_buf = NULL,
> + .len = ARRAY_SIZE(sca_data->txbuf),
> + .delay = delay,
> + .cs_change = 1,
> + },
> + {
> + .tx_buf = NULL,
> + .rx_buf = sca_data->rxbuf,
> + .len = ARRAY_SIZE(sca_data->rxbuf),
> + .delay = delay,
> + .cs_change = 0,
> + }
> + };
> +
> + /* inverted crc value as described in device data sheet */
> + crc = ~crc8(sca3300_crc_table, &sca_data->txbuf[0], 3, CRC8_INIT_VALUE);
> + sca_data->txbuf[3] = crc;
> +
> + ret = spi_sync_transfer(sca_data->spi, xfers, ARRAY_SIZE(xfers));
> + if (ret < 0) {
> + dev_err(&sca_data->spi->dev,
> + "transfer error, error: %d\n", ret);
> + return -EIO;
Why shadowing error code?
> + }
> +
> + crc = ~crc8(sca3300_crc_table, &sca_data->rxbuf[0], 3, CRC8_INIT_VALUE);
> + if (sca_data->rxbuf[3] != crc) {
> + dev_err(&sca_data->spi->dev, "CRC checksum mismatch");
> + return -EIO;
> + }
> +
> + /* get return status */
> + rs = sca_data->rxbuf[0] & 0x03;
What's 0x3? Shouldn't it be defined with a descriptive name?
> + if (rs == SCA3300_RS_ERROR)
> + ret = -EINVAL;
> +
> + *val = sign_extend32(get_unaligned_be16(&sca_data->rxbuf[1]), 15);
> +
> + return ret;
> +}
...
> +static int sca3300_error_handler(struct sca3300_data *sca_data)
> +{
> + int ret;
> + int val;
> +
> + mutex_lock(&sca_data->lock);
> + sca_data->txbuf[0] = 0x0 | (SCA3300_REG_STATUS << 2);
> + ret = sca3300_transfer(sca_data, &val);
> + mutex_unlock(&sca_data->lock);
> + /* return status is cleared after reading status register */
> + if (ret != -EINVAL) {
Why this? Comment above is confusing, see also the comments below.
> + dev_err(&sca_data->spi->dev,
> + "error reading device status: %d\n", ret);
> + return ret;
> + }
> + dev_err(&sca_data->spi->dev, "device status: 0x%x\n",
> + (u16)(val & SCA3300_STATUS_MASK));
Why casting here?!
> + return 0;
> +}
...
> +static int sca3300_read_reg(struct sca3300_data *sca_data, u8 reg, int *val)
> +{
> + int ret;
> +
> + mutex_lock(&sca_data->lock);
> + sca_data->txbuf[0] = 0x0 | (reg << 2);
What is the meaning of the 0x0? Comment, please.
> + ret = sca3300_transfer(sca_data, val);
> + mutex_unlock(&sca_data->lock);
> + if (ret == -EINVAL)
This needs a good comment.
> + ret = sca3300_error_handler(sca_data);
> +
> + return ret;
if (ret != -EINVAL)
return ret;
return _error_handler(...);
> +}
> +
> +static int sca3300_write_reg(struct sca3300_data *sca_data, u8 reg, int val)
> +{
> + int reg_val = 0;
> + int ret;
> +
> + mutex_lock(&sca_data->lock);
> + sca_data->txbuf[0] = BIT(7) | (reg << 2);
> + put_unaligned_be16(val, &sca_data->txbuf[1]);
> + ret = sca3300_transfer(sca_data, ®_val);
> + mutex_unlock(&sca_data->lock);
> + if (ret == -EINVAL)
> + ret = sca3300_error_handler(sca_data);
> +
> + return ret;
> +}
As per above.
...
> + for (i = 0; i < ARRAY_SIZE(sca3300_accel_scale); i++) {
> + if (val2 == sca3300_accel_scale[i][1]) {
> + idx = i;
Redundant variable. Refactor w/o using it. It's easy.
> + break;
> + }
> + }
> + if (idx == -1)
> + return -EINVAL;
...
> + /* freq. change is possible only for mode 3 and 4 */
> + if (reg_val == 2 && val == sca3300_lp_freq[3])
> + return sca3300_write_reg(data, SCA3300_REG_MODE, 3);
> + else if (reg_val == 3 && val == sca3300_lp_freq[2])
> + return sca3300_write_reg(data, SCA3300_REG_MODE, 2);
> + else
> + return -EINVAL;
Two times redundant 'else'
...
> +static irqreturn_t sca3300_trigger_handler(int irq, void *p)
> +{
> + struct iio_poll_func *pf = p;
> + struct iio_dev *indio_dev = pf->indio_dev;
> + struct sca3300_data *data = iio_priv(indio_dev);
> + int bit, ret, val, i = 0;
> +
> + for_each_set_bit(bit, indio_dev->active_scan_mask,
> + indio_dev->masklength) {
> + ret = sca3300_read_reg(data, sca3300_channels[bit].address,
> + &val);
> + if (ret < 0) {
> + dev_err(&data->spi->dev,
> + "failed to read register, error: %d\n", ret);
> + goto out;
> + }
> + ((s16 *)data->scan.channels)[i++] = val;
> + }
> +
> + iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
> + iio_get_time_ns(indio_dev));
> +out:
> + iio_trigger_notify_done(indio_dev->trig);
> +
> + return IRQ_HANDLED;
> +}
> +
...
> + ret = sca3300_write_reg(sca_data, SCA3300_REG_MODE,
> + SCA3300_VALUE_SW_RESET);
> + if (ret != 0)
if (ret)
Everywhere in the code.
> + return ret;
+ blank line
> + /* wait at least 1ms after SW-reset command */
> + usleep_range(1e3, 10e3);
This doesn't make any difference. You may simply drop it and unify the comments.
> + /* wait 15ms for settling of signal paths */
> + usleep_range(15e3, 50e3);
...
> + if (value != SCA3300_DEVICE_ID) {
> + dev_err(&sca_data->spi->dev,
> + "device id not expected value, %d != %u\n",
> + value, SCA3300_DEVICE_ID);
> + return -EIO;
-ENODEV ?
> + }
...
> +static int sca3300_debugfs_reg_access(struct iio_dev *indio_dev,
> + unsigned int reg, unsigned int writeval,
> + unsigned int *readval)
> +{
> + struct sca3300_data *data = iio_priv(indio_dev);
> + int value;
> + int ret;
> +
> + if (reg > SCA3300_SELBANK)
> + return -EINVAL;
> +
> + if (!readval)
> + return sca3300_write_reg(data, reg, writeval);
> + ret = sca3300_read_reg(data, reg, &value);
> + if (ret < 0)
> + return ret;
> + *readval = (unsigned int)value;
While casting?
> + return 0;
> +}
If you switch to use regmap, the read part will be a bonus automatically.
...
> + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*sca_data));
> + if (!indio_dev) {
> + dev_err(&spi->dev,
> + "failed to allocate memory for iio device\n");
Noice. You will get the same from user space.
> + return -ENOMEM;
> + }
...
> + indio_dev->dev.parent = &spi->dev;
This is done by IIO core.
...
> + ret = devm_iio_device_register(&spi->dev, indio_dev);
> + if (ret < 0) {
> + dev_err(&spi->dev, "iio device register failed, error: %d\n",
> + ret);
> + return ret;
> + }
> +
> + return 0;
return ret;
> +}
...
> +static const struct of_device_id sca3300_dt_ids[] = {
> + { .compatible = "murata,sca3300"},
> + {},
Drop comma. No need for a terminator line.
> +};
...
> +static struct spi_driver sca3300_driver = {
> + .driver = {
> + .name = SCA3300_ALIAS,
> + .owner = THIS_MODULE,
Redundant.
> + .of_match_table = of_match_ptr(sca3300_dt_ids),
Drop of_match_ptr(). In 99% its use is wrong.
> + },
> +
> + .probe = sca3300_probe,
> +};
--
With Best Regards,
Andy Shevchenko
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