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

Guenter Roeck
2020-09-05T15:18:09Z

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.

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);
>
>