Date:   Mon, 24 Apr 2017 22:32:56 +0200
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jonathan Cameron <jic23@...nel.org>
Cc:     linux-iio@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sascha Weisenberger <sascha.weisenberger@...mens.com>
Subject: Re: [PATCH] iio: adc: Add support for TI ADC1x8s102

On 2017-04-24 22:05, Andy Shevchenko wrote:
> On Mon, 2017-04-24 at 21:28 +0200, Jan Kiszka wrote:
>> This is an upstream port of an IIO driver for the TI ADC108S102 and
>> ADC128S102. The former can be found on the Intel Galileo Gen2 and the
>> Siemens SIMATIC IOT2000. For those boards, ACPI-based enumeration is
>> included.
>>
>> Original author: Bogdan Pricop <bogdan.pricop@...tex.com>
>> Ported from Intel Galileo Gen2 BSP to Intel Yocto kernel:
>> Todor Minchev <todor@...chev.co.uk>.
> 
>> +#include <linux/interrupt.h>
>> +#include <linux/module.h>
>> +#include <linux/spi/spi.h>
>> +
>> +#include <linux/platform_data/adc1x8s102.h>
>> +#include <linux/regulator/consumer.h>
>> +
>> +#include <linux/delay.h>
>> +#include <linux/acpi.h>
>> +#include <linux/property.h>
>> +#include <linux/gpio.h>
>> +
>> +#include <linux/spi/pxa2xx_spi.h>
> 
> Perhaps alphabetical order?
> 
>> +
>> +/* 16-bit SPI command format:
>> + *   [15:14] Ignored
>> + *   [13:11] 3-bit channel address
>> + *   [10:0]  Ignored
>> + */
>> +#define ADC1x8S102_CMD(ch)		(((ch) << (8)) << (3))
> 
> I guess ((u16)(ch) << 11) would be slightly better.
> 
>> +
>> +/*
>> + * 16-bit SPI response format:
>> + *   [15:12] Zeros
>> + *   [11:0]  12-bit ADC sample (for ADC108S102, [1:0] will always be
>> 0).
>> + */
> 
>> +#define ADC1x8S102_RES_DATA(res)	(res & ((1 <<
>> ADC1x8S102_BITS) - 1))
> 
> GENMASK() and to align with above
> 
> ((u16)(res) & GENMASK(11, 0))
> 
>> +	/* SPI message buffers:
>> +	 *  tx_buf: |C0|C1|C2|C3|C4|C5|C6|C7|XX|
>> +	 *  rx_buf: |XX|R0|R1|R2|R3|R4|R5|R6|R7|tt|tt|tt|tt|
>> +	 *
>> +	 *  tx_buf: 8 channel read commands, plus 1 dummy command
>> +	 *  rx_buf: 1 dummy response, 8 channel responses, plus 64-
>> bit timestamp
>> +	 */
>> +	__be16				rx_buf[13]
>> ____cacheline_aligned;
>> +	__be16				tx_buf[9];
> 
> Would it be better to have tx_buf with ____cache_aligned? (IIUC it's
> already by fact of above, though...)
> 
>> +};
> 
>> tatic int adc1x8s102_update_scan_mode(struct iio_dev *indio_dev,
>> +		unsigned long const *active_scan_mask)
>> +{
>> +	struct adc1x8s102_state *st;
>> +	int i, j;
>> +
>> +	st = iio_priv(indio_dev);
>> +
> 
>> +	/* Fill in the first x shorts of tx_buf with the number of
>> channels
>> +	 * enabled for sampling by the triggered buffer
>> +	 */
> 
> /*
>  * Is it okay style for
>  * multi-line comments?
>  */
> 
>> +	for (i = 0, j = 0; i < ADC1x8S102_MAX_CHANNELS; i++) {
>> +		if (test_bit(i, active_scan_mask)) {
> 
> for_each_set_bit() 
> 
>> +			st->tx_buf[j] =
>> cpu_to_be16(ADC1x8S102_CMD(i));
>> +			j++;
>> +		}
>> +	}
>> +	/* One dummy command added, to clock in the last response */
>> +	st->tx_buf[j] = 0x00;
> 
>> +}
>> +
> 
>> +static int adc1x8s102_read_raw(struct iio_dev *indio_dev,
>> +			   struct iio_chan_spec const *chan,
> 
>> +			   int *val,
>> +			   int *val2,
>> +			   long m)
> 
> One line?
> 
>> +{
>> +	int ret;
>> +	struct adc1x8s102_state *st;
>> +
>> +	st = iio_priv(indio_dev);
>> +
>> +	switch (m) {
>> +	case IIO_CHAN_INFO_RAW:
>> +		mutex_lock(&indio_dev->mlock);
>> +		if (indio_dev->currentmode == INDIO_BUFFER_TRIGGERED)
>> {
>> +			ret = -EBUSY;
> 
>> +			dev_warn(&st->spi->dev,
>> +			 "indio_dev->currentmode is
>> INDIO_BUFFER_TRIGGERED\n");
> 
> Indentation?
> 

All valid remarks, will address.

>> +		} else {
>> +			ret = adc1x8s102_scan_direct(st, chan-
>>> address);
>> +		}
>> +		mutex_unlock(&indio_dev->mlock);
>> +
>> +		if (ret < 0)
>> +			return ret;
>> +		*val = ADC1x8S102_RES_DATA(ret);
>> +
>> +		return IIO_VAL_INT;
>> +	case IIO_CHAN_INFO_SCALE:
>> +		switch (chan->type) {
>> +		case IIO_VOLTAGE:
>> +			if (st->reg)
>> +				*val = regulator_get_voltage(st->reg) 
>> / 1000;
>> +			else
>> +				*val = st->ext_vin;
>> +
>> +			*val2 = chan->scan_type.realbits;
>> +			return IIO_VAL_FRACTIONAL_LOG2;
>> +		default:
>> +			dev_warn(&st->spi->dev,
>> +				 "Invalid channel type %u for channel
>> %d\n",
>> +				 chan->type, chan->channel);
>> +			return -EINVAL;
>> +		}
>> +	default:
>> +		dev_warn(&st->spi->dev, "Invalid IIO_CHAN_INFO:
>> %lu\n", m);
>> +		return -EINVAL;
>> +	}
>> +}
> 
>> +#ifdef CONFIG_ACPI
>> +typedef int (*acpi_setup_handler)(struct spi_device *,
>> +				  const struct
>> adc1x8s102_platform_data **);
>> +
>> +static const struct adc1x8s102_platform_data int3495_platform_data =
>> {
>> +	.ext_vin = 5000,	/* 5 V */
>> +};
>> +
> 
>> +/* Galileo Gen 2 SPI setup */
>> +static int
>> +adc1x8s102_setup_int3495(struct spi_device *spi,
>> +			 const struct adc1x8s102_platform_data
>> **pdata)
>> +{
> 
>> +	struct pxa2xx_spi_chip *chip_data;
> 
> This one is too big to waste memory on one member.
> 
>> +
>> +	chip_data = devm_kzalloc(&spi->dev, sizeof(*chip_data),
>> GFP_KERNEL);
>> +	if (!chip_data)
>> +		return -ENOMEM;
>> +
>> +	chip_data->gpio_cs = ADC1x8S102_GALILEO2_CS;
>> +	spi->controller_data = chip_data;
>> +	dev_info(&spi->dev, "setting GPIO CS value to %d\n",
>> +		 chip_data->gpio_cs);
>> +	spi_setup(spi);
>> +
>> +	*pdata = &int3495_platform_data;
>> +
>> +	return 0;
>> +}
> 
> This is weird approach.

Let me dig deeper if are allowed to pass a static struct here as well.
But the struct is driver-defined.

> Moreover, please do not use platform data at all.

That is just following pre-existing pattern, just look around in the
iio/adc folder, not to speak of others. But I'm open to learn about any
newer pattern there is.

> 
>> +
>> +static const struct acpi_device_id adc1x8s102_acpi_ids[] = {
>> +	{ "INT3495",  (kernel_ulong_t)&adc1x8s102_setup_int3495 },
>> +	{ }
>> +};
>> +MODULE_DEVICE_TABLE(acpi, adc1x8s102_acpi_ids);
>> +#endif
>> +
>> +static int adc1x8s102_probe(struct spi_device *spi)
>> +{
>> +	const struct adc1x8s102_platform_data *pdata = spi-
>>> dev.platform_data;
>> +	struct adc1x8s102_state *st;
>> +	struct iio_dev *indio_dev;
>> +	int ret;
>> +
> 
>> +#ifdef CONFIG_ACPI
> 
> No.

...because?

> 
>> +	if (ACPI_COMPANION(&spi->dev)) {
>> +		acpi_setup_handler setup_handler;
>> +		const struct acpi_device_id *id;
>> +
>> +		id = acpi_match_device(adc1x8s102_acpi_ids, &spi-
>>> dev);
>> +		if (!id)
>> +			return -ENODEV;
>> +
> 
>> +		setup_handler = (acpi_setup_handler)id->driver_data;
>> +		if (setup_handler) {
>> +			ret = setup_handler(spi, &pdata);
>> +			if (ret)
>> +				return ret;
>> +		}
> 
> No way.

Constructive feedback, please.

> 
>> +	}
>> +#endif
>> +
>> +	if (!pdata) {
>> +		dev_err(&spi->dev, "Cannot get adc1x8s102 platform
>> data\n");
>> +		return -ENODEV;
>> +	}
>> +
> 
>> +error_cleanup_ring:
>> +	iio_triggered_buffer_cleanup(indio_dev);
>> +error_disable_reg:
>> +	regulator_disable(st->reg);
> 
> Does devm_() help to get rid of these?

Yep. See also other drivers.

> 
>> +
>> +	return ret;
>> +}
> 
>> +
>> +static int adc1x8s102_remove(struct spi_device *spi)
>> +{
>> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
>> +	struct adc1x8s102_state *st = iio_priv(indio_dev);
>> +
> 
>> +	iio_device_unregister(indio_dev);
>> +	iio_triggered_buffer_cleanup(indio_dev);
>> +
>> +	regulator_disable(st->reg);
> 
> Ditto.
> 
>> +
>> +	return 0;
>> +}
>> +
> 
>> +++ b/include/linux/platform_data/adc1x8s102.h
> 
> It must be no such file at all!
> Please, remove it completely.

Not without explaining what the new style is. As I said, the existing
driver use that as well. The fact that there is no OF binding yet
exploiting this should be no excuse IMHO.

Jan

-- 
Siemens AG, Corporate Technology, CT RDA ITP SES-DE
Corporate Competence Center Embedded Linux

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