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Message-ID: <20150106181842.GA618@roeck-us.net>
Date: Tue, 6 Jan 2015 10:18:42 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc: Patrick Titiano <ptitiano@...libre.com>,
LKML <linux-kernel@...r.kernel.org>,
Benoit Cousson <bcousson@...libre.com>,
LM Sensors <lm-sensors@...sensors.org>
Subject: Re: [v8, 5/5] hwmon: ina2xx: allow to change the averaging rate at
run-time
On Mon, Jan 05, 2015 at 03:20:56PM +0100, Bartosz Golaszewski wrote:
> The averaging rate of ina226 is hardcoded to 16 in the driver. Make it
> modifiable at run-time via a new sysfs attribute.
>
> While we're at it - add an additional variable to ina2xx_data, which holds
> the current configuration settings - this way we'll be able to restore the
> configuration in case of an unexpected chip reset.
>
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> ---
> Documentation/hwmon/ina2xx | 3 ++
> drivers/hwmon/ina2xx.c | 129 +++++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 128 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/hwmon/ina2xx b/Documentation/hwmon/ina2xx
> index 320dd69..a11256d 100644
> --- a/Documentation/hwmon/ina2xx
> +++ b/Documentation/hwmon/ina2xx
> @@ -48,3 +48,6 @@ The shunt value in micro-ohms can be set via platform data or device tree at
> compile-time or via the shunt_resistor attribute in sysfs at run-time. Please
> refer to the Documentation/devicetree/bindings/i2c/ina2xx.txt for bindings
> if the device tree is used.
> +
> +The averaging rate of INA226 and INA230 can be changed via the avg_rate sysfs
> +attribute. The available rates are: 1, 4, 16, 64, 128, 256, 512 and 1024.
You do accept other values, so you might want to add that other values will be
rounded to the above.
> diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
> index 49537ea..6f6aebd 100644
> --- a/drivers/hwmon/ina2xx.c
> +++ b/drivers/hwmon/ina2xx.c
> @@ -68,6 +68,15 @@
>
> #define INA2XX_RSHUNT_DEFAULT 10000
>
> +/* bit masks for the averaging setting in the configuration register */
> +#define INA226_AVG_RD_MASK 0x0E00
> +#define INA226_AVG_WR_MASK 0xF1FF
You could define INA226_AVG_MASK as 0x0e00 and use ~INA226_AVG_MASK to negate
it. This is more common than the above and less error prone.
> +
> +#define INA226_READ_AVG(reg) ((reg & INA226_AVG_RD_MASK) >> 9)
(reg)
Also, it might make sense to define INA226_AVG_SHIFT since you use it twice.
> +
> +/* common attrs, ina226 attrs and NULL */
> +#define INA2XX_MAX_ATTRIBUTE_GROUPS 3
> +
> enum ina2xx_ids { ina219, ina226 };
>
> struct ina2xx_config {
> @@ -85,12 +94,14 @@ struct ina2xx_data {
> const struct ina2xx_config *config;
>
> long rshunt;
> + u16 curr_config;
>
> struct mutex update_lock;
> bool valid;
> unsigned long last_updated;
>
> int kind;
> + const struct attribute_group *groups[INA2XX_MAX_ATTRIBUTE_GROUPS];
> u16 regs[INA2XX_MAX_REGISTERS];
> };
>
> @@ -115,6 +126,39 @@ static const struct ina2xx_config ina2xx_config[] = {
> },
> };
>
> +/*
> + * Available averaging rates for ina226. The indices correspond with
> + * the bit values expected by the chip (according to the ina226 datasheet,
> + * table 3 AVG bit settings, found at
> + * http://www.ti.com/lit/ds/symlink/ina226.pdf.
> + */
> +static const int ina226_avg_tab[] = { 1, 4, 16, 64, 128, 256, 512, 1024 };
> +
> +static int ina226_avg_bits(int avg)
> +{
> + int i;
> +
> + /* Get the closest average from the tab. */
> + for (i = 0; i < ARRAY_SIZE(ina226_avg_tab) - 1; i++) {
> + if (avg <= (ina226_avg_tab[i] + ina226_avg_tab[i + 1]) / 2)
> + return i;
> + }
> +
> + return i; /* Return 0b0111 for other values. */
> +}
> +
> +static int ina226_avg_val(int bits)
> +{
> + /*
> + * Value read from the config register should be correct, but do check
> + * the boundary just in case.
> + */
> + if (bits >= ARRAY_SIZE(ina226_avg_tab))
> + return -ENODEV;
> +
Logically this can not happen, since the calling code uses INA226_READ_AVG()
which can only return 0..7. So this check is really unnecessary. It might
possibly make sense to pass in the configuration register value and apply
INA226_READ_AVG in this function to make this more obvious. See more below,
though; the function itself is unnecessary.
> + return ina226_avg_tab[bits];
> +}
> +
> static int ina2xx_calibrate(struct ina2xx_data *data)
> {
> return i2c_smbus_write_word_swapped(data->client, INA2XX_CALIBRATION,
> @@ -131,7 +175,7 @@ static int ina2xx_init(struct ina2xx_data *data)
>
> /* device configuration */
> ret = i2c_smbus_write_word_swapped(client, INA2XX_CONFIG,
> - data->config->config_default);
> + data->curr_config);
> if (ret < 0)
> return ret;
>
> @@ -292,6 +336,62 @@ static ssize_t ina2xx_set_shunt(struct device *dev,
> return count;
> }
>
> +static ssize_t ina226_show_avg(struct device *dev,
> + struct device_attribute *da, char *buf)
> +{
> + struct ina2xx_data *data = ina2xx_update_device(dev);
> + int avg, i;
> +
> + if (IS_ERR(data))
> + return PTR_ERR(data);
> +
> + avg = ina226_avg_val(INA226_READ_AVG(data->regs[INA2XX_CONFIG]));
> + if (avg < 0)
> + return avg;
> +
> + for (i = 0; i < ARRAY_SIZE(ina226_avg_tab); i++) {
> + if (avg == ina226_avg_tab[i])
> + break;
ina226_avg_val() calculates the average value from ina226_avg_tab
and then you loop through ina226_avg_tab to find the index into ina226_avg_tab
again, only to use the thus calculated index for accessing ina226_avg_tab[]
once more. Think about it. A simple
avg = ina226_avg_tab[INA226_READ_AVG(data->regs[INA2XX_CONFIG])];
return snprintf(buf, PAGE_SIZE, "%d\n", avg);
or even
return snprintf(buf, PAGE_SIZE, "%d\n",
ina226_avg_tab[INA226_READ_AVG(data->regs[INA2XX_CONFIG])]);
would accomplish exactly the same.
> + }
> +
> + return snprintf(buf, PAGE_SIZE, "%d\n", ina226_avg_tab[i]);
> +}
> +
> +static ssize_t ina226_set_avg(struct device *dev,
> + struct device_attribute *da,
> + const char *buf, size_t count)
> +{
> + struct ina2xx_data *data = dev_get_drvdata(dev);
> + unsigned long val;
> + int status, avg;
> +
> + if (IS_ERR(data))
> + return PTR_ERR(data);
> +
> + status = kstrtoul(buf, 10, &val);
> + if (status < 0)
> + return status;
> +
> + if (val > INT_MAX || val == 0)
> + return -EINVAL;
> +
> + avg = ina226_avg_bits(val);
> +
> + mutex_lock(&data->update_lock);
> + data->curr_config = (data->regs[INA2XX_CONFIG] &
> + INA226_AVG_WR_MASK) | (avg << 9);
> + status = i2c_smbus_write_word_swapped(data->client,
> + INA2XX_CONFIG,
> + data->curr_config);
> + /* Make sure the next access re-reads all registers. */
> + data->valid = 0;
> + mutex_unlock(&data->update_lock);
> + if (status < 0)
> + return status;
> +
> + return count;
> +}
> +
> /* shunt voltage */
> static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, ina2xx_show_value, NULL,
> INA2XX_SHUNT_VOLTAGE);
> @@ -313,6 +413,10 @@ static SENSOR_DEVICE_ATTR(shunt_resistor, S_IRUGO | S_IWUSR,
> ina2xx_show_value, ina2xx_set_shunt,
> INA2XX_CALIBRATION);
>
> +/* averaging rate */
> +static SENSOR_DEVICE_ATTR(avg_rate, S_IRUGO | S_IWUSR,
I kind of dislike that attribute name. I don't have a better idea though, so
I'll let it pass unless you have a better idea.
> + ina226_show_avg, ina226_set_avg, 0);
> +
> /* pointers to created device attributes */
> static struct attribute *ina2xx_attrs[] = {
> &sensor_dev_attr_in0_input.dev_attr.attr,
> @@ -322,7 +426,19 @@ static struct attribute *ina2xx_attrs[] = {
> &sensor_dev_attr_shunt_resistor.dev_attr.attr,
> NULL,
> };
> -ATTRIBUTE_GROUPS(ina2xx);
> +
> +static const struct attribute_group ina2xx_group = {
> + .attrs = ina2xx_attrs,
> +};
> +
> +static struct attribute *ina226_attrs[] = {
> + &sensor_dev_attr_avg_rate.dev_attr.attr,
> + NULL,
> +};
> +
> +static const struct attribute_group ina226_group = {
> + .attrs = ina226_attrs,
> +};
>
> static int ina2xx_probe(struct i2c_client *client,
> const struct i2c_device_id *id)
> @@ -333,7 +449,7 @@ static int ina2xx_probe(struct i2c_client *client,
> struct ina2xx_data *data;
> struct device *hwmon_dev;
> u32 val;
> - int ret;
> + int ret, group = 0;
>
> if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WORD_DATA))
> return -ENODEV;
> @@ -355,6 +471,7 @@ static int ina2xx_probe(struct i2c_client *client,
> /* set the device type */
> data->kind = id->driver_data;
> data->config = &ina2xx_config[data->kind];
> + data->curr_config = data->config->config_default;
> data->client = client;
>
> if (data->rshunt <= 0 ||
> @@ -369,8 +486,12 @@ static int ina2xx_probe(struct i2c_client *client,
>
> mutex_init(&data->update_lock);
>
> + data->groups[group++] = &ina2xx_group;
> + if (data->kind == ina226)
> + data->groups[group++] = &ina226_group;
> +
> hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
> - data, ina2xx_groups);
> + data, data->groups);
> if (IS_ERR(hwmon_dev))
> return PTR_ERR(hwmon_dev);
>
--
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