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Date: Wed, 17 Apr 2019 06:46:50 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Nicolin Chen <nicoleotsuka@...il.com>, jdelvare@...e.com
Cc: linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
corbet@....net, linux-doc@...r.kernel.org
Subject: Re: [PATCH] hwmon: (ina3221) Add voltage conversion time settings
On 4/16/19 4:55 PM, Nicolin Chen wrote:
> The CONFIG register has two 3-bit fields for conversion time
> settings of Bus-voltage and Shunt-voltage, respectively. The
> conversion settings, along with averaging mode, allow users
> to optimize available timing requirement.
>
> This patch adds an 'update_interval' sysfs node through the
> hwmon_chip_info of hwmon core. It reflects a total hardware
> conversion time:
> samples * channels * (Bus + Shunt conversion times)
>
> Though INA3221 supports different conversion time setups for
> Bus and Shunt voltages, this patch only adds the support of
> a unified setting for both conversion times, by dividing the
> conversion time into two equal values.
>
> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
> ---
>
> Hi Guenter,
>
> I am not quite sure if this update_interval is the best way to
> implement the conversion time settings but I can't find another
> common approach. This implementation certainly has drawbacks:
> 1) It can't configure Bus and Shunt conversion times separately
> (Not crucial for me at this point as I set them equally)
> 2) Users need to calculate for the settings of conversion time
> 3) The ABI defines update_interval in msec while the hardware
> and datasheet does in usec, and that generates rounding diff
> 4) The update_interval value would be spontaneously modified
> everytime number of samples or number of enabled channels
> gets changed. This might confuses users who tries to have
> a fixed update_interval other than really merely setting
> conversion time.
>
> I see IIO subsystem have something like IIO_CHAN_INFO_INT_TIME
> for conversion time setting exclusively. Do we have something
> similar under hwmon?
>
No. I think what you have should be good enough for now.
Please see comments below.
Thanks,
Guenter
> Thanks
>
> Documentation/hwmon/ina3221 | 9 +++++
> drivers/hwmon/ina3221.c | 65 ++++++++++++++++++++++++++++++++-----
> 2 files changed, 65 insertions(+), 9 deletions(-)
>
> diff --git a/Documentation/hwmon/ina3221 b/Documentation/hwmon/ina3221
> index ed3f22769d4b..3b05170112f0 100644
> --- a/Documentation/hwmon/ina3221
> +++ b/Documentation/hwmon/ina3221
> @@ -38,3 +38,12 @@ in[456]_input Shunt voltage(uV) for channels 1, 2, and 3 respectively
> samples Number of samples using in the averaging mode.
> Supports the list of number of samples:
> 1, 4, 16, 64, 128, 256, 512, 1024
> +update_interval Data conversion time in millisecond, following:
> + update_interval = C x S x (BC + SC)
> + C: number of enabled channels
> + S: number of samples
> + BC: bus-voltage conversion time in millisecond
> + SC: shunt-voltage conversion time in millisecond
> + Affects both Bus- and Shunt-voltage conversion time.
> + Note that setting update_interval to 0ms sets both BC
> + and SC to 140 us (minimum conversion time).
> diff --git a/drivers/hwmon/ina3221.c b/drivers/hwmon/ina3221.c
> index 74d39d212931..af4ab8ddddce 100644
> --- a/drivers/hwmon/ina3221.c
> +++ b/drivers/hwmon/ina3221.c
> @@ -144,19 +144,37 @@ static const int ina3221_avg_samples[] = {
> 1, 4, 16, 64, 128, 256, 512, 1024,
> };
>
> -static inline int ina3221_wait_for_data(struct ina3221_data *ina)
> +/* Converting update_interval in msec to conversion time in usec */
> +static inline u32 ina3221_interval_ms_to_conv_time(u16 config, int interval)
> {
> - u32 channels = hweight16(ina->reg_config & INA3221_CONFIG_CHs_EN_MASK);
> - u32 vbus_ct_idx = INA3221_CONFIG_VBUS_CT(ina->reg_config);
> - u32 vsh_ct_idx = INA3221_CONFIG_VSH_CT(ina->reg_config);
> - u32 samples_idx = INA3221_CONFIG_AVG(ina->reg_config);
> + u32 channels = hweight16(config & INA3221_CONFIG_CHs_EN_MASK);
> + u32 samples_idx = INA3221_CONFIG_AVG(config);
> + u32 samples = ina3221_avg_samples[samples_idx];
> +
> + /* Bisect the result to Bus and Shunt conversion times */
> + return DIV_ROUND_CLOSEST(interval * 1000 / 2, channels * samples);
> +}
> +
> +/* Converting CONFIG register value to update_interval in usec */
> +static inline u32 ina3221_reg_to_interval_us(u16 config)
> +{
> + u32 channels = hweight16(config & INA3221_CONFIG_CHs_EN_MASK);
> + u32 vbus_ct_idx = INA3221_CONFIG_VBUS_CT(config);
> + u32 vsh_ct_idx = INA3221_CONFIG_VSH_CT(config);
> + u32 samples_idx = INA3221_CONFIG_AVG(config);
> u32 samples = ina3221_avg_samples[samples_idx];
> u32 vbus_ct = ina3221_conv_time[vbus_ct_idx];
> u32 vsh_ct = ina3221_conv_time[vsh_ct_idx];
> - u32 wait, cvrf;
>
> /* Calculate total conversion time */
> - wait = channels * (vbus_ct + vsh_ct) * samples;
> + return channels * (vbus_ct + vsh_ct) * samples;
> +}
> +
> +static inline int ina3221_wait_for_data(struct ina3221_data *ina)
> +{
> + u32 wait, cvrf;
> +
> + wait = ina3221_reg_to_interval_us(ina->reg_config);
>
> /* Polling the CVRF bit to make sure read data is ready */
> return regmap_field_read_poll_timeout(ina->fields[F_CVRF],
> @@ -197,6 +215,11 @@ static int ina3221_read_chip(struct device *dev, u32 attr, long *val)
> regval = INA3221_CONFIG_AVG(ina->reg_config);
> *val = ina3221_avg_samples[regval];
> return 0;
> + case hwmon_chip_update_interval:
> + /* Return in msec */
> + *val = ina3221_reg_to_interval_us(ina->reg_config);
> + *val = DIV_ROUND_CLOSEST(*val, 1000);
> + return 0;
> default:
> return -EOPNOTSUPP;
> }
> @@ -308,7 +331,7 @@ static int ina3221_read_curr(struct device *dev, u32 attr,
> static int ina3221_write_chip(struct device *dev, u32 attr, long val)
> {
> struct ina3221_data *ina = dev_get_drvdata(dev);
> - int ret, idx;
> + int ret, idx, tmp;
>
> switch (attr) {
> case hwmon_chip_samples:
> @@ -321,6 +344,28 @@ static int ina3221_write_chip(struct device *dev, u32 attr, long val)
> if (ret)
> return ret;
>
> + /* Update reg_config accordingly */
> + return regmap_read(ina->regmap, INA3221_CONFIG,
> + &ina->reg_config);
> + case hwmon_chip_update_interval:
> + tmp = ina3221_interval_ms_to_conv_time(ina->reg_config, val);
> + idx = find_closest(tmp, ina3221_conv_time,
> + ARRAY_SIZE(ina3221_conv_time));
> +
> + /* Update Bus-voltage conversion time */
> + ret = regmap_update_bits(ina->regmap, INA3221_CONFIG,
> + INA3221_CONFIG_VBUS_CT_MASK,
> + idx << INA3221_CONFIG_VBUS_CT_SHIFT);
> + if (ret)
> + return ret;
> +
> + /* Update Shunt-voltage conversion time */
> + ret = regmap_update_bits(ina->regmap, INA3221_CONFIG,
> + INA3221_CONFIG_VSH_CT_MASK,
> + idx << INA3221_CONFIG_VSH_CT_SHIFT);
> + if (ret)
> + return ret;
It should be possible to update both conversion times with a single call,
since both calls touch only one register. Something like
ret = regmap_update_bits(ina->regmap, INA3221_CONFIG
INA3221_CONFIG_VBUS_CT_MASK | INA3221_CONFIG_VSH_CT_MASK,
(idx << INA3221_CONFIG_VBUS_CT_SHIFT) | (idx << INA3221_CONFIG_VSH_CT_SHIFT));
Granted, that is a bit long, but it saves an extra i2c write operation.
> +
> /* Update reg_config accordingly */
> return regmap_read(ina->regmap, INA3221_CONFIG,
> &ina->reg_config);
> @@ -482,6 +527,7 @@ static umode_t ina3221_is_visible(const void *drvdata,
> case hwmon_chip:
> switch (attr) {
> case hwmon_chip_samples:
> + case hwmon_chip_update_interval:
> return 0644;
> default:
> return 0;
> @@ -527,7 +573,8 @@ static umode_t ina3221_is_visible(const void *drvdata,
>
> static const struct hwmon_channel_info *ina3221_info[] = {
> HWMON_CHANNEL_INFO(chip,
> - HWMON_C_SAMPLES),
> + HWMON_C_SAMPLES,
> + HWMON_C_UPDATE_INTERVAL),
> HWMON_CHANNEL_INFO(in,
> /* 0: dummy, skipped in is_visible */
> HWMON_I_INPUT,
>
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