Re: [PATCH 4/6] hwmon: amd_energy: let user enable/disable the sw accumulation

Guenter Roeck
2020-09-05T15:33:40Z

On 9/5/20 8:17 AM, Guenter Roeck wrote:
> On 9/5/20 7:32 AM, Naveen Krishna Chatradhi wrote:
>> Provide an option "accumulator_status" via sysfs to enable/disable
>> the software accumulation of energy counters.
>>
>> Signed-off-by: Naveen Krishna Chatradhi <nchatrad@amd.com>
>
> I am quite substantially opposed to this. I'd be willing to
> accept a module parameter. However, the code is there, and it is
> enabled by default, and it should stay enabled by default.
> I don't want to have to deal with people complaining that
> it suddenly no longer works.
>
> Also, there needs to be an explanation for why this is needed.
>

No, wait, without accumulator this driver has zero value.
Users should just not load the driver if they don't want the
overhead associated with accumulation.

Guenter

> Guenter
>
>> ---
>> drivers/hwmon/amd_energy.c | 104 ++++++++++++++++++++++++++++++-------
>> 1 file changed, 86 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/hwmon/amd_energy.c b/drivers/hwmon/amd_energy.c
>> index 96c61784d05c..c294bea56c02 100644
>> --- a/drivers/hwmon/amd_energy.c
>> +++ b/drivers/hwmon/amd_energy.c
>> @@ -32,6 +32,8 @@
>> #define AMD_ENERGY_UNIT_MASK 0x01F00
>> #define AMD_ENERGY_MASK 0xFFFFFFFF
>>
>> +static struct device_attribute accumulate_attr;
>> +
>> struct sensor_accumulator {
>> u64 energy_ctr;
>> u64 prev_value;
>> @@ -42,10 +44,12 @@ struct amd_energy_data {
>> const struct hwmon_channel_info *info[2];
>> struct hwmon_chip_info chip;
>> struct task_struct *wrap_accumulate;
>> + struct device *hwmon_dev;
>> /* Lock around the accumulator */
>> struct mutex lock;
>> /* An accumulator for each core and socket */
>> struct sensor_accumulator *accums;
>> + bool accumulator_status;
>> /* Energy Status Units */
>> u64 energy_units;
>> unsigned int timeout;
>> @@ -128,13 +132,15 @@ static void amd_add_delta(struct amd_energy_data *data, int ch,
>> rdmsrl_safe_on_cpu(cpu, reg, &input);
>> input &= AMD_ENERGY_MASK;
>>
>> - accum = &data->accums[ch];
>> - if (input >= accum->prev_value)
>> - input += accum->energy_ctr -
>> - accum->prev_value;
>> - else
>> - input += UINT_MAX - accum->prev_value +
>> - accum->energy_ctr;
>> + if (data->accumulator_status) {
>> + accum = &data->accums[ch];
>> + if (input >= accum->prev_value)
>> + input += accum->energy_ctr -
>> + accum->prev_value;
>> + else
>> + input += UINT_MAX - accum->prev_value +
>> + accum->energy_ctr;
>> + }
>>
>> /* Energy consumed = (1/(2^ESU) * RAW * 1000000UL) μJoules */
>> *val = div64_ul(input * 1000000UL, BIT(data->energy_units));
>> @@ -264,9 +270,67 @@ static int amd_create_sensor(struct device *dev,
>> return 0;
>> }
>>
>> +static ssize_t amd_energy_accumulate_show(struct device *dev,
>> + struct device_attribute *dev_attr,
>> + char *buf)
>> +{
>> + struct amd_energy_data *data = dev_get_drvdata(dev);
>> +
>> + return sprintf(buf, "%d\n", data->accumulator_status);
>> +}
>> +
>> +static ssize_t amd_energy_accumulate_store(struct device *dev,
>> + struct device_attribute *dev_attr,
>> + const char *buf, size_t count)
>> +{
>> + struct amd_energy_data *data = dev_get_drvdata(dev);
>> + bool input;
>> + int ret;
>> +
>> + ret = kstrtobool(buf, &input);
>> + if (ret)
>> + return ret;
>> +
>> + if (data->accumulator_status == input)
>> + return count;
>> +
>> + if (input) {
>> + memset(data->accums, 0, (data->nr_cpus + data->nr_socks) *
>> + sizeof(struct sensor_accumulator));
>> +
>> + if (!data->wrap_accumulate) {
>> + data->wrap_accumulate =
>> + kthread_run(energy_accumulator,
>> + data, "%s", dev_name(dev));
>> + if (IS_ERR(data->wrap_accumulate))
>> + return PTR_ERR(data->wrap_accumulate);
>> + }
>> + } else {
>> + if (data && data->wrap_accumulate) {
>> + ret = kthread_stop(data->wrap_accumulate);
>> + if (ret)
>> + return ret;
>> + data->wrap_accumulate = NULL;
>> + }
>> + }
>> + data->accumulator_status = input;
>> +
>> + return count;
>> +}
>> +
>> +static int create_accumulate_status_file(struct amd_energy_data *data)
>> +{
>> + accumulate_attr.attr.name = "accumulator_status";
>> + accumulate_attr.attr.mode = 0664;
>> + accumulate_attr.show = amd_energy_accumulate_show;
>> + accumulate_attr.store = amd_energy_accumulate_store;
>> +
>> + return sysfs_create_file(&data->hwmon_dev->kobj,
>> + &accumulate_attr.attr);
>> +}
>> +
>> static int amd_energy_probe(struct platform_device *pdev)
>> {
>> - struct device *hwmon_dev;
>> struct amd_energy_data *data;
>> struct device *dev = &pdev->dev;
>> int ret;
>> @@ -290,12 +354,12 @@ static int amd_energy_probe(struct platform_device *pdev)
>> mutex_init(&data->lock);
>> get_energy_units(data);
>>
>> - hwmon_dev = devm_hwmon_device_register_with_info(dev, DRVNAME,
>> - data,
>> - &data->chip,
>> - NULL);
>> - if (IS_ERR(hwmon_dev))
>> - return PTR_ERR(hwmon_dev);
>> + data->hwmon_dev = devm_hwmon_device_register_with_info(dev, DRVNAME,
>> + data,
>> + &data->chip,
>> + NULL);
>> + if (IS_ERR(data->hwmon_dev))
>> + return PTR_ERR(data->hwmon_dev);
>>
>> /* Once in 3 minutes for a resolution of 1/2*16 */
>> if (data->energy_units == 0x10)
>> @@ -305,10 +369,12 @@ static int amd_energy_probe(struct platform_device *pdev)
>> if (data->energy_units == 0x6)
>> data->timeout = 3 * 24 * 60 * 60;
>>
>> - data->wrap_accumulate = kthread_run(energy_accumulator, data,
>> - "%s", dev_name(hwmon_dev));
>> - if (IS_ERR(data->wrap_accumulate))
>> - return PTR_ERR(data->wrap_accumulate);
>> + /* Disabling the energy accumulation by default */
>> + data->accumulator_status = 0;
>> +
>> + ret = create_accumulate_status_file(data);
>> + if (ret)
>> + return ret;
>>
>> return 0;
>> }
>> @@ -317,6 +383,8 @@ static int amd_energy_remove(struct platform_device *pdev)
>> {
>> struct amd_energy_data *data = dev_get_drvdata(&pdev->dev);
>>
>> + sysfs_remove_file(&data->hwmon_dev->kobj, &accumulate_attr.attr);
>> +
>> if (data && data->wrap_accumulate)
>> kthread_stop(data->wrap_accumulate);
>>
>>
>