Date:   Tue, 13 Dec 2016 21:22:35 +0100 (CET)
From:   Peter Meerwald-Stadler <pmeerw@...erw.net>
To:     Andreas Klinger <ak@...klinger.de>
cc:     devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, robh+dt@...nel.org,
        pawel.moll@....com, mark.rutland@....com,
        ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
        jic23@...nel.org, knaack.h@....de, lars@...afoo.de
Subject: Re: [PATCH 2/2] iio: adc: hx711: Add IIO driver for AVIA HX711


> This is the IIO driver for AVIA HX711 ADC which ist mostly used in weighting
> cells.

comments below
 
> The protocol is quite simple and using GPIO's:

GPIOs

> One GPIO is used as clock (SCK) while another GPIO is read (DOUT)
> 
> Signed-off-by: Andreas Klinger <ak@...klinger.de>
> ---
>  drivers/iio/adc/Kconfig  |  13 +++
>  drivers/iio/adc/Makefile |   1 +
>  drivers/iio/adc/hx711.c  | 269 +++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 283 insertions(+)
>  create mode 100644 drivers/iio/adc/hx711.c
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 932de1f9d1e7..7902b50fcf32 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -205,6 +205,19 @@ config HI8435
>  	  This driver can also be built as a module. If so, the module will be
>  	  called hi8435.
>  
> +config HX711
> +	tristate "AVIA HX711 ADC for weight cells"
> +	depends on GPIOLIB
> +	help
> +	  If you say yes here you get support for AVIA HX711 ADC which is used
> +	  for weight cells
> +
> +	  This driver uses two GPIO's, one for setting the clock and the other

GPIOs

> +	  one for getting the data
> +
> +	  This driver can also be built as a module. If so, the module will be
> +	  called hx711.
> +
>  config INA2XX_ADC
>  	tristate "Texas Instruments INA2xx Power Monitors IIO driver"
>  	depends on I2C && !SENSORS_INA2XX
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index b1aa456e6af3..d46e289900ef 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -21,6 +21,7 @@ obj-$(CONFIG_CC10001_ADC) += cc10001_adc.o
>  obj-$(CONFIG_DA9150_GPADC) += da9150-gpadc.o
>  obj-$(CONFIG_EXYNOS_ADC) += exynos_adc.o
>  obj-$(CONFIG_HI8435) += hi8435.o
> +obj-$(CONFIG_HX711) += hx711.o
>  obj-$(CONFIG_IMX7D_ADC) += imx7d_adc.o
>  obj-$(CONFIG_INA2XX_ADC) += ina2xx-adc.o
>  obj-$(CONFIG_LP8788_ADC) += lp8788_adc.o
> diff --git a/drivers/iio/adc/hx711.c b/drivers/iio/adc/hx711.c
> new file mode 100644
> index 000000000000..cbc89e467985
> --- /dev/null
> +++ b/drivers/iio/adc/hx711.c
> @@ -0,0 +1,269 @@
> +/*
> + * HX711: analog to digital converter for weight sensor module
> + *
> + * Copyright (c) Andreas Klinger <ak@...klinger.de>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + */
> +#include <linux/err.h>
> +#include <linux/gpio.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/property.h>
> +#include <linux/slab.h>
> +#include <linux/sched.h>
> +#include <linux/delay.h>
> +#include <linux/iio/iio.h>
> +
> +#define HX711_GAIN_32		2	/* gain = 32 for channel B  */
> +#define HX711_GAIN_64		3	/* gain = 64 for channel A  */
> +#define HX711_GAIN_128		1	/* gain = 128 for channel A */
> +

only one newline here please

> +
> +struct hx711_data {
> +	struct device		*dev;
> +	dev_t			devt;

devt is not used, delete

> +	struct gpio_desc	*gpiod_sck;
> +	struct gpio_desc	*gpiod_dout;
> +	int			gain_pulse;
> +	struct mutex		lock;
> +};
> +
> +static void hx711_reset(struct hx711_data *hx711_data)
> +{
> +	int val;
> +	int i;
> +
> +	val = gpiod_get_value(hx711_data->gpiod_dout);
> +	if (val) {
> +		dev_warn(hx711_data->dev, "RESET-HX711\n");

message needed?

> +
> +		gpiod_set_value(hx711_data->gpiod_sck, 1);
> +		udelay(80);
> +		gpiod_set_value(hx711_data->gpiod_sck, 0);
> +
> +		for (i = 0; i < 1000; i++) {
> +			val = gpiod_get_value(hx711_data->gpiod_dout);
> +			if (!val)
> +				break;
> +			/* sleep at least 1 ms*/

add space before */

> +			msleep(1);
> +		}

can this fail? what is it takes longer than 1000 * 1ms?

> +	}
> +}
> +
> +static int hx711_cycle(struct hx711_data *hx711_data)
> +{
> +	int val;
> +
> +	/* if preempted for more then 60us while SCK is high:
> +	 * hx711 is going in reset
> +	 * ==> measuring is false
> +	 */
> +	preempt_disable();
> +	gpiod_set_value(hx711_data->gpiod_sck, 1);
> +	val = gpiod_get_value(hx711_data->gpiod_dout);
> +	gpiod_set_value(hx711_data->gpiod_sck, 0);
> +	preempt_enable();
> +
> +	return val;
> +}
> +
> +static unsigned int hx711_read(struct hx711_data *hx711_data)
> +{
> +	int i;
> +	int ret;
> +	int wert = 0;

val or value maybe?
should be unsigned int to match the return type of the function

> +
> +	hx711_reset(hx711_data);
> +
> +	for (i = 0; i < 24; i++) {
> +		wert <<= 1;
> +		ret = hx711_cycle(hx711_data);
> +		if (ret)
> +			wert++;
> +	}
> +
> +	wert ^= 0x800000;
> +
> +	for (i = 0; i < hx711_data->gain_pulse; i++)
> +		ret = hx711_cycle(hx711_data);
> +
> +	return wert;
> +}
> +

delete newline

> +
> +static int hx711_read_raw(struct iio_dev *iio_dev,
> +				const struct iio_chan_spec *chan,
> +				int *val, int *val2, long mask)
> +{
> +	struct hx711_data *hx711_data = iio_priv(iio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		switch (chan->type) {
> +		case IIO_VOLTAGE:
> +			mutex_lock(&hx711_data->lock);
> +			*val = (int)hx711_read(hx711_data);
> +			mutex_unlock(&hx711_data->lock);
> +			ret = IIO_VAL_INT;

return IIO_VAL_INT;

> +			break;
> +		default:
> +			return -EINVAL;
> +		}
> +		return ret;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return ret;

delete, dead code

> +}
> +
> +static const struct iio_info hx711_iio_info = {
> +	.driver_module		= THIS_MODULE,
> +	.read_raw		= hx711_read_raw,
> +};
> +
> +static const struct iio_chan_spec hx711_chan_spec[] = {
> +	{ .type = IIO_VOLTAGE,
> +		.channel = 0,

.channel = 0 not needed, there is only one channel

> +		.info_mask_separate =
> +			BIT(IIO_CHAN_INFO_RAW),
> +		.scan_type = {

scan_type not needed, driver does not support buffered reads

> +			.sign = 'u',
> +			.realbits = 24,
> +			.storagebits = 32,
> +			.shift = 0,
> +		}
> +	},
> +};
> +
> +static int hx711_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *node = dev->of_node;
> +	struct hx711_data *hx711_data = NULL;
> +	struct iio_dev *iio;
> +	int ret = 0, ival;
> +
> +	iio = devm_iio_device_alloc(dev, sizeof(struct hx711_data));
> +	if (!iio) {
> +		dev_err(dev, "failed to allocate IIO device\n");
> +		return -ENOMEM;
> +	}
> +
> +	hx711_data = iio_priv(iio);
> +	hx711_data->dev = dev;
> +
> +	mutex_init(&hx711_data->lock);
> +
> +	hx711_data->gpiod_sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_HIGH);
> +	if (IS_ERR(hx711_data->gpiod_sck)) {
> +		ret = PTR_ERR(hx711_data->gpiod_sck);
> +		goto err;
> +	}
> +
> +	hx711_data->gpiod_dout = devm_gpiod_get(dev, "dout", GPIOD_OUT_HIGH);
> +	if (IS_ERR(hx711_data->gpiod_dout)) {
> +		ret = PTR_ERR(hx711_data->gpiod_dout);
> +		goto err;
> +	}
> +
> +	ret = of_property_read_u32 (node, "gain", &ival);
> +	if (!ret) {
> +		switch (ival) {
> +		case 32:
> +			hx711_data->gain_pulse = HX711_GAIN_32;
> +			break;
> +		case 64:
> +			hx711_data->gain_pulse = HX711_GAIN_64;
> +			break;
> +		case 128:

merge default and case 128?

> +			hx711_data->gain_pulse = HX711_GAIN_128;
> +			break;
> +		default:
> +			hx711_data->gain_pulse = HX711_GAIN_128;
> +		}
> +	} else
> +		hx711_data->gain_pulse = HX711_GAIN_128;
> +	dev_dbg(hx711_data->dev, "gain: %d\n", hx711_data->gain_pulse);
> +
> +	ret = gpiod_direction_input(hx711_data->gpiod_dout);
> +	if (ret < 0) {
> +		dev_err(hx711_data->dev, "gpiod_direction_input: %d\n", ret);
> +		goto err;
> +	}
> +
> +	ret = gpiod_direction_output(hx711_data->gpiod_sck, 0);
> +	if (ret < 0) {
> +		dev_err(hx711_data->dev, "gpiod_direction_output: %d\n", ret);
> +		goto err;
> +	}
> +
> +	platform_set_drvdata(pdev, iio);
> +
> +	iio->name = pdev->name;
> +	iio->dev.parent = &pdev->dev;
> +	iio->info = &hx711_iio_info;
> +	iio->modes = INDIO_DIRECT_MODE;
> +	iio->channels = hx711_chan_spec;
> +	iio->num_channels = ARRAY_SIZE(hx711_chan_spec);
> +
> +	dev_err(hx711_data->dev, "initialized\n");

excessive logging, please remove

> +
> +	return devm_iio_device_register(dev, iio);
> +
> +err:
> +	return ret;

just return directly without goto?

> +}
> +
> +
> +static int hx711_suspend(struct device *dev)
> +{

pointless, just don't do PM support

> +	return 0;
> +}
> +
> +static int hx711_resume(struct device *dev)
> +{
> +	return 0;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(hx711_pm_ops, hx711_suspend, hx711_resume);
> +
> +
> +static const struct of_device_id of_hx711_match[] = {
> +	{ .compatible = "avia,hx711", },
> +	{},
> +};
> +
> +MODULE_DEVICE_TABLE(of, of_hx711_match);
> +
> +static struct platform_driver hx711_driver = {
> +	.probe		= hx711_probe,
> +	.driver		= {
> +		.name		= "hx711-gpio",
> +		.pm		= &hx711_pm_ops,
> +		.of_match_table	= of_hx711_match,
> +	},
> +};
> +
> +module_platform_driver(hx711_driver);
> +
> +MODULE_AUTHOR("Andreas Klinger <ak@...klinger.de>");
> +MODULE_DESCRIPTION("HX711 bitbanging driver - ADC for weight cells");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:hx711-gpio");
> +
> 

-- 

Peter Meerwald-Stadler
+43-664-2444418 (mobile)

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