Date:	Fri, 24 Aug 2012 11:45:05 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Krystian Garbaciak <krystian.garbaciak@...semi.com>
Cc:	linux-kernel@...r.kernel.org, rtc-linux@...glegroups.com,
	lm-sensors@...sensors.org, linux-input@...r.kernel.org,
	linux-watchdog@...r.kernel.org, linux-leds@...r.kernel.org,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Liam Girdwood <lrg@...com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Jean Delvare <khali@...ux-fr.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Ashish Jangam <ashish.jangam@...tcummins.com>,
	Andrew Jones <drjones@...hat.com>,
	Donggeun Kim <dg77.kim@...sung.com>,
	Philippe Rétornaz <philippe.retornaz@...l.ch>,
	Wim Van Sebroeck <wim@...ana.be>,
	Bryan Wu <bryan.wu@...onical.com>,
	"Richard Purdie <rpurdie@...ys.net> Anthony Olech" 
	<anthony.olech@...semi.com>
Subject: Re: [RFC PATCH 4/8] hwmon: Add DA906x hardware monitoring support.

On Fri, Aug 24, 2012 at 03:05:00PM +0100, Krystian Garbaciak wrote:
> DA906x PMIC provides ADC for voltage and temperature monitoring.
> 
Hi Krystian,

DA906x seems to be a bad choice for a name. It covers DA906[0-9] and possibly
even DA906[A-Z]. The only chip really in existence seems to be DA9064.

I personally think it is a bad idea to have an 'x' in a driver name. What if
DA9069 shows up at some point and is completely different ? I think the driver
should be named for the first supported chip; reference the others in the code
and documentation.

Worse, I find no information anywhere in your patch set indicating which chips
are actually supported. I don't know how other subsystems handle this, but for
hwmon this is a no-go.

> The driver provides results of following ADC channels:
>  - in0 - system voltage (2500 - 5500 mV)
>  - in1 - universal voltage channel #1 (0 - 2500 mV)
>  - in2 - universal voltage channel #2 (0 - 2500 mV)
>  - in3 - universal voltage channel #3 (0 - 2500 mV)
>  - in4 - backup battery voltage (0 - 5000 mV)
>  - temp1 - PMIC internal junction temperature (-88 - 333 Celcius degrees)
> 
> Signed-off-by: Krystian Garbaciak <krystian.garbaciak@...semi.com>
> ---
>  drivers/hwmon/Kconfig        |    6 +
>  drivers/hwmon/Makefile       |    1 +
>  drivers/hwmon/da906x-hwmon.c |  393 ++++++++++++++++++++++++++++++++++++++++++

Also please provide Documentation/hwmon/da906x-hwmon.

>  3 files changed, 400 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/hwmon/da906x-hwmon.c
> 
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index b0a2e4c..7abc9a0 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1373,6 +1373,12 @@ config SENSORS_WM8350
>  	  This driver can also be built as a module.  If so, the module
>  	  will be called wm8350-hwmon.
>  
> +config SENSORS_DA906X
> +	tristate "DA906X HWMON device drivers"
> +	depends on MFD_DA906X
> +	help
> +	  Support for the HWMON DA906X device driver.
> +

Alphabetical order, please, and describe which chip(s) are supported. And you
don't really support a device driver, the device driver presumably supports a
chip. Since it is tristate, we also expect you to provide the module name if the
driver is built as module.

>  config SENSORS_ULTRA45
>  	tristate "Sun Ultra45 PIC16F747"
>  	depends on SPARC64
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 7aa9811..ffbe151 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -43,6 +43,7 @@ obj-$(CONFIG_SENSORS_ASC7621)	+= asc7621.o
>  obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o
>  obj-$(CONFIG_SENSORS_CORETEMP)	+= coretemp.o
>  obj-$(CONFIG_SENSORS_DA9052_ADC)+= da9052-hwmon.o
> +obj-$(CONFIG_SENSORS_DA906X)	+= da906x-hwmon.o
>  obj-$(CONFIG_SENSORS_DME1737)	+= dme1737.o
>  obj-$(CONFIG_SENSORS_DS620)	+= ds620.o
>  obj-$(CONFIG_SENSORS_DS1621)	+= ds1621.o
> diff --git a/drivers/hwmon/da906x-hwmon.c b/drivers/hwmon/da906x-hwmon.c
> new file mode 100644
> index 0000000..8ece931
> --- /dev/null
> +++ b/drivers/hwmon/da906x-hwmon.c
> @@ -0,0 +1,393 @@
> +/*
> + * HW Monitor support for Dialog DA906X PMIC series
> + *
> + * Copyright 2012 Dialog Semiconductor Ltd.
> + *
> + * Author: Krystian Garbaciak <krystian.garbaciak@...semi.com>,
> + *         Michal Hajduk <michal.hajduk@...semi.com>
> + *
> + *  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.
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/err.h>
> +#include <linux/delay.h>
> +#include <linux/init.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +#include <linux/platform_device.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +#include <linux/mfd/da906x/core.h>
> +#include <linux/mfd/da906x/pdata.h>
> +
> +/* ADC resolutions for manual and auto modes */
> +#define DA906X_ADC_RES		\
> +		(1 << (DA906X_ADC_RES_L_BITS + DA906X_ADC_RES_M_BITS))
> +#define DA906X_ADC_MAX		(DA906X_ADC_RES - 1)
> +#define	DA906X_ADC_AUTO_RES	(1 << DA906X_ADC_RES_M_BITS)
> +#define	DA906X_ADC_AUTO_MAX	(DA906X_ADC_AUTO_RES - 1)
> +
> +/* Define interpolation table to calculate ADC values  */
> +struct i_table {
> +	int x0;
> +	int a;
> +	int b;
> +};
> +#define ILINE(x1, x2, y1, y2)	{ \
> +		.x0 = (x1), \
> +		.a = ((y2) - (y1)) * DA906X_ADC_RES / ((x2) - (x1)), \
> +		.b = (y1) - ((y2) - (y1)) * (x1) / ((x2) - (x1)), \
> +	}
> +
> +struct channel_info {
> +	const char *name;
> +	const struct i_table *tbl;
> +	int tbl_max;
> +	u16 reg_auto_en;
> +};
> +
> +enum da906x_adc {
> +	DA906X_VSYS,
> +	DA906X_ADCIN1,
> +	DA906X_ADCIN2,
> +	DA906X_ADCIN3,
> +	DA906X_TJUNC,
> +	DA906X_VBBAT,
> +
> +	DA906X_CHAN_NUM
> +};
> +
> +static const struct i_table vsys_tbl[] = {
> +	ILINE(0, DA906X_ADC_MAX, 2500, 5500)
> +};
> +
> +static const struct i_table adcin_tbl[] = {
> +	ILINE(0, DA906X_ADC_MAX, 0, 2500)
> +};
> +
> +static const struct i_table tjunc_tbl[] = {
> +	ILINE(0, DA906X_ADC_MAX, 333, -86)
> +};
> +
> +static const struct i_table vbbat_tbl[] = {
> +	ILINE(0, DA906X_ADC_MAX, 0, 5000)
> +};

Since the first parameter to ILINE is always 0, it is not needed. This means
that x0 in itable is also always 0 and thus not needed. 

> +
> +static const struct channel_info da906x_channels[] = {
> +	[DA906X_VSYS]	= { "VSYS",
> +			    vsys_tbl, ARRAY_SIZE(vsys_tbl) - 1,
> +			    DA906X_REG_VSYS_RES },
> +	[DA906X_ADCIN1]	= { "ADCIN1",
> +			    adcin_tbl,	ARRAY_SIZE(adcin_tbl) - 1,
> +			    DA906X_REG_ADCIN1_RES },
> +	[DA906X_ADCIN2]	= { "ADCIN2",
> +			    adcin_tbl,	ARRAY_SIZE(adcin_tbl) - 1,
> +			    DA906X_REG_ADCIN2_RES },
> +	[DA906X_ADCIN3]	= { "ADCIN3",
> +			    adcin_tbl,	ARRAY_SIZE(adcin_tbl) - 1,
> +			    DA906X_REG_ADCIN3_RES },
> +	[DA906X_TJUNC]	= { "TJUNC",
> +			    tjunc_tbl,	ARRAY_SIZE(tjunc_tbl) - 1 },
> +	[DA906X_VBBAT]	= { "VBBAT",
> +			    vbbat_tbl,	ARRAY_SIZE(vbbat_tbl) - 1}

	s/1}/1 }/

> +};

You lost me here a bit (I am missing something ?).

Seems to be each table has exactly one entry. Since the table size is 1,
ARRAY_SIZE(vbbat_tbl) - 1 is 0, and ...

> +#define DA906X_ADC_AUTO_MODE_SUPPORT_MASK	(DA906X_ADC_AUTO_VSYS_EN | \
> +						 DA906X_ADC_AUTO_AD1_EN | \
> +						 DA906X_ADC_AUTO_AD2_EN | \
> +						 DA906X_ADC_AUTO_AD3_EN)
> +
> +struct da906x_hwmon {
> +	struct da906x *da906x;
> +	struct device *class_dev;
> +	struct completion man_adc_rdy;	/* Manual read completion flag */
> +	struct mutex hwmon_mutex;	/* Queue concurent manual reads */
> +	int irq;
> +	u8 adc_auto_en;     /* Bitmask of channels with auto mode enabled */
> +	s8 tjunc_offset;    /* Calibration offset for junction temperature */
> +};
> +
> +int da906x_adc_convert(int channel, int x)
> +{
> +	const struct channel_info *info = &da906x_channels[channel];
> +	int i, ret;
> +
> +	for (i = info->tbl_max; i > 0; i--)
> +		if (info->tbl[i].x0 <= x)
> +			break;

... this loop never does anything because info->tbl_max is always 0.
Besides, even if the loop was used, x0 is always 0 anyway, so you might well
compare against 0 instead which doesn't make sense.

So what is the point for making the code that complex ? For me it just adds a
lot of confusion.

> +
> +	ret = info->tbl[i].a * x;
> +	if (ret >= 0)
> +		ret += DA906X_ADC_RES / 2;
> +	else
> +		ret -= DA906X_ADC_RES / 2;
> +	ret = ret / DA906X_ADC_RES + info->tbl[i].b;

	ret = DIV_ROUND_CLOSEST(ret, DA906X_ADC_RES) + info->tbl[i].b;

has the same effect as the 5 lines above and is simpler.

> +	return ret;
> +}
> +
> +static int da906x_adc_manual_read(struct da906x_hwmon *hwmon, int channel)
> +{
> +	int ret;
> +	u8 data[2];
> +
> +	mutex_lock(&hwmon->hwmon_mutex);
> +
> +	init_completion(&hwmon->man_adc_rdy);
> +
> +	/* Start measurment on selected channel */
> +	data[0] = (channel << DA906X_ADC_MUX_SHIFT) & DA906X_ADC_MUX_MASK;
> +	data[0] |= DA906X_ADC_MAN;
> +	ret = da906x_reg_update(hwmon->da906x, DA906X_REG_ADC_MAN,
> +				DA906X_ADC_MUX_MASK | DA906X_ADC_MAN, data[0]);
> +	if (ret < 0)
> +		goto out;
> +
> +	/* Wait for interrupt from ADC */
> +	ret = wait_for_completion_timeout(&hwmon->man_adc_rdy,
> +					  msecs_to_jiffies(1000));
> +	if (ret == 0) {
> +		ret = -EBUSY;

Should this be -ETIMEDOUT ?

> +		goto out;
> +	}
> +
> +	/* Get results */
> +	ret = da906x_block_read(hwmon->da906x, DA906X_REG_ADC_RES_L, 2, data);
> +	if (ret < 0)
> +		goto out;
> +	ret = (data[0] & DA906X_ADC_RES_L_MASK) >> DA906X_ADC_RES_L_SHIFT;
> +	ret |= data[1] << DA906X_ADC_RES_L_BITS;
> +out:
> +	mutex_unlock(&hwmon->hwmon_mutex);
> +	return ret;
> +}
> +
> +static int da906x_adc_auto_read(struct da906x *da906x, int channel)
> +{
> +	const struct channel_info *info = &da906x_channels[channel];
> +
> +	return da906x_reg_read(da906x, info->reg_auto_en);
> +}
> +
> +static irqreturn_t da906x_hwmon_irq_handler(int irq, void *irq_data)
> +{
> +	struct da906x_hwmon *hwmon = irq_data;
> +
> +	complete(&hwmon->man_adc_rdy);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static ssize_t da906x_adc_read(struct device *dev,
> +			       struct device_attribute *devattr, char *buf)
> +{
> +	struct da906x_hwmon *hwmon = dev_get_drvdata(dev);
> +	int channel = to_sensor_dev_attr(devattr)->index;
> +	int val;
> +
> +	if (hwmon->adc_auto_en & (1 << channel)) {
> +		val = da906x_adc_auto_read(hwmon->da906x, channel);
> +		if (val < 0)
> +			return val;
> +
> +		val *= DA906X_ADC_RES / DA906X_ADC_AUTO_RES;
> +		val = da906x_adc_convert(channel, val);
> +	} else {
> +		val = da906x_adc_manual_read(hwmon, channel);
> +		if (val < 0)
> +			return val;
> +
> +		if (channel == DA906X_TJUNC)
> +			val += hwmon->tjunc_offset;
> +		val = da906x_adc_convert(channel, val);

This call is really the same for both the if and else path. Might as well put it
after the conditional code.

> +	}
> +
> +	return sprintf(buf, "%d\n", val);
> +}
> +
> +static ssize_t da906x_show_name(struct device *dev,
> +	struct device_attribute *attr, char *buf)


Please align all multi-line function parameters with the opening (.

> +{
> +	return sprintf(buf, DA906X_DRVNAME_HWMON "\n");
> +}
> +
> +static ssize_t da906x_show_label(struct device *dev,
> +				 struct device_attribute *devattr, char *buf)
> +{
> +	const struct channel_info *info;
> +
> +	info = &da906x_channels[to_sensor_dev_attr(devattr)->index];
> +	return sprintf(buf, "%s\n", info->name);
> +}
> +
> +/* Vsys voltage */
> +static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO,
> +			  da906x_adc_read, NULL, DA906X_VSYS);
> +static SENSOR_DEVICE_ATTR(in0_label, S_IRUGO,
> +			  da906x_show_label, NULL, DA906X_VSYS);
> +
> +/* Universal ADC channel #1 */
> +static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO,
> +			  da906x_adc_read, NULL, DA906X_ADCIN1);
> +static SENSOR_DEVICE_ATTR(in1_label, S_IRUGO,
> +			  da906x_show_label, NULL, DA906X_ADCIN1);
> +
> +/* Universal ADC channel #2 */
> +static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO,
> +			  da906x_adc_read, NULL,
> +			  DA906X_ADCIN2);
> +static SENSOR_DEVICE_ATTR(in2_label, S_IRUGO,
> +			  da906x_show_label, NULL, DA906X_ADCIN2);
> +
> +/* Universal ADC channel #3 */
> +static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO,
> +			  da906x_adc_read, NULL, DA906X_ADCIN3);
> +static SENSOR_DEVICE_ATTR(in3_label, S_IRUGO,
> +			  da906x_show_label, NULL, DA906X_ADCIN3);
> +
> +/* Backup battery voltage */
> +static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO,
> +			  da906x_adc_read, NULL, DA906X_VBBAT);
> +static SENSOR_DEVICE_ATTR(in4_label, S_IRUGO,
> +			  da906x_show_label, NULL, DA906X_VBBAT);
> +
> +/* Junction temperature */
> +static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
> +			  da906x_adc_read, NULL, DA906X_TJUNC);
> +
> +static SENSOR_DEVICE_ATTR(temp1_label, S_IRUGO,
> +			  da906x_show_label, NULL, DA906X_TJUNC);
> +
> +/* Device name */
> +static DEVICE_ATTR(name, S_IRUGO, da906x_show_name, NULL);
> +
> +static struct attribute *da906x_attributes[] = {
> +	&dev_attr_name.attr,
> +	&sensor_dev_attr_in0_input.dev_attr.attr,
> +	&sensor_dev_attr_in0_label.dev_attr.attr,
> +	&sensor_dev_attr_in1_input.dev_attr.attr,
> +	&sensor_dev_attr_in1_label.dev_attr.attr,
> +	&sensor_dev_attr_in2_input.dev_attr.attr,
> +	&sensor_dev_attr_in2_label.dev_attr.attr,
> +	&sensor_dev_attr_in3_input.dev_attr.attr,
> +	&sensor_dev_attr_in3_label.dev_attr.attr,
> +	&sensor_dev_attr_in4_input.dev_attr.attr,
> +	&sensor_dev_attr_in4_label.dev_attr.attr,
> +	&sensor_dev_attr_temp1_input.dev_attr.attr,
> +	&sensor_dev_attr_temp1_label.dev_attr.attr,
> +	NULL
> +};
> +
> +static const struct attribute_group da906x_attr_group = {
> +	.attrs = da906x_attributes,
> +};
> +
> +static int __devinit da906x_hwmon_probe(struct platform_device *pdev)
> +{
> +	struct da906x *da906x = dev_get_drvdata(pdev->dev.parent);
> +	struct da906x_pdata *da906x_pdata = dev_get_platdata(da906x->dev);
> +	struct da906x_hwmon *hwmon;
> +	int ret;
> +
> +	hwmon = devm_kzalloc(&pdev->dev, sizeof(struct da906x_hwmon),
> +			     GFP_KERNEL);
> +	if (!hwmon)
> +		return -ENOMEM;
> +
> +	mutex_init(&hwmon->hwmon_mutex);
> +	init_completion(&hwmon->man_adc_rdy);
> +	hwmon->da906x = da906x;
> +
> +	ret = da906x_reg_read(da906x, DA906X_REG_ADC_CONT);
> +	if (ret < 0)
> +		return ret;
> +	hwmon->adc_auto_en = ret & DA906X_ADC_AUTO_MODE_SUPPORT_MASK;
> +
> +	if (da906x_pdata->flags & DA906X_FLG_FORCE_IN0_MANUAL_MODE)

You should check if da906x_pdata is NULL before using it.

> +		hwmon->adc_auto_en &= ~DA906X_ADC_AUTO_VSYS_EN;
> +	else if (da906x_pdata->flags & DA906X_FLG_FORCE_IN0_AUTO_MODE)
> +		hwmon->adc_auto_en |= DA906X_ADC_AUTO_VSYS_EN;
> +
> +	if (da906x_pdata->flags & DA906X_FLG_FORCE_IN1_MANUAL_MODE)
> +		hwmon->adc_auto_en &= ~DA906X_ADC_AUTO_AD1_EN;
> +	else if (da906x_pdata->flags & DA906X_FLG_FORCE_IN1_AUTO_MODE)
> +		hwmon->adc_auto_en |= DA906X_ADC_AUTO_AD1_EN;
> +
> +	if (da906x_pdata->flags & DA906X_FLG_FORCE_IN2_MANUAL_MODE)
> +		hwmon->adc_auto_en &= ~DA906X_ADC_AUTO_AD2_EN;
> +	else if (da906x_pdata->flags & DA906X_FLG_FORCE_IN2_AUTO_MODE)
> +		hwmon->adc_auto_en |= DA906X_ADC_AUTO_AD2_EN;
> +
> +	if (da906x_pdata->flags & DA906X_FLG_FORCE_IN3_MANUAL_MODE)
> +		hwmon->adc_auto_en &= ~DA906X_ADC_AUTO_AD3_EN;
> +	else if (da906x_pdata->flags & DA906X_FLG_FORCE_IN3_AUTO_MODE)
> +		hwmon->adc_auto_en |= DA906X_ADC_AUTO_AD3_EN;
> +
> +	ret = da906x_reg_update(da906x, DA906X_REG_ADC_CONT,
> +				DA906X_ADC_AUTO_MODE_SUPPORT_MASK,
> +				hwmon->adc_auto_en);
> +	if (ret < 0)
> +		return ret;
> +
> +	hwmon->class_dev = hwmon_device_register(&pdev->dev);
> +	if (IS_ERR(hwmon->class_dev))
> +		return PTR_ERR(hwmon->class_dev);
> +
hwmon registration has to be the last call, after sysfs attributes exist.
sysfs entries are expected to exist when the hwmon device is registered.

> +	hwmon->irq = platform_get_irq_byname(pdev, DA906X_DRVNAME_HWMON);

This function can return an error (-ENXIO).

> +	ret = devm_request_threaded_irq(&pdev->dev, hwmon->irq, NULL,
> +					da906x_hwmon_irq_handler,
> +					IRQF_TRIGGER_LOW | IRQF_ONESHOT,
> +					"HWMON", hwmon);
> +	if (ret) {
> +		dev_err(&pdev->dev, "Failed to request IRQ.\n");
> +		goto err;
> +	}
> +
> +	platform_set_drvdata(pdev, hwmon);
> +
> +	ret = da906x_reg_read(da906x, DA906X_REG_T_OFFSET);
> +	if (ret < 0)
> +		dev_warn(&pdev->dev, "Could not read temp1 callibration offset.\n");

	s/callibration/calibration/

> +	else
> +		hwmon->tjunc_offset = (s8)ret;
> +
> +	ret = sysfs_create_group(&pdev->dev.kobj, &da906x_attr_group);
> +	if (ret)
> +		goto err;
> +
> +	return 0;
> +
> +err:
> +	hwmon_device_unregister(hwmon->class_dev);
> +	return ret;
> +}
> +
> +static int __devexit da906x_hwmon_remove(struct platform_device *pdev)
> +{
> +	struct da906x_hwmon *hwmon = platform_get_drvdata(pdev);
> +
> +	hwmon_device_unregister(hwmon->class_dev);
> +	sysfs_remove_group(&pdev->dev.kobj, &da906x_attr_group);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver da906x_hwmon_driver = {
> +	.probe = da906x_hwmon_probe,
> +	.remove = __devexit_p(da906x_hwmon_remove),
> +	.driver = {
> +		.name = DA906X_DRVNAME_HWMON,
> +		.owner = THIS_MODULE,
> +	},
> +};
> +
> +module_platform_driver(da906x_hwmon_driver);
> +
> +MODULE_DESCRIPTION("DA906X Hardware monitoring");
> +MODULE_AUTHOR("Krystian Garbaciak <krystian.garbaciak@...semi.com>, Michal Hajduk <michal.hajduk@...semi.com>");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("paltform:" DA906X_DRVNAME_HWMON);

s/paltform/platform/

> -- 
> 1.7.0.4
> 
> 
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