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Date: Wed, 17 Apr 2019 07:04:09 -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 4/17/19 6:46 AM, Guenter Roeck wrote:
> 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.
>
Thinking about it ... does it even make sense to cache reg_config twice,
or would it be better to just update the local copy and use regmap_write()
to send it to the chip ?
Guenter
>> +
>> /* 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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