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

Naveen Krishna Ch
2020-09-08T16:22:04Z

Hi Guenter

On Tue, 8 Sep 2020 at 21:42, Chatradhi, Naveen Krishna
<NaveenKrishna.Chatradhi@amd.com> wrote:
>
> [AMD Public Use]
>
> [CAUTION: External Email]
>
> 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.
Sure, I will change it back.

> > I don't want to have to deal with people complaining that it suddenly
> > no longer works.
Understood.
> >
> > 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.

The use case we have is to provide an interface to enable/disable
accumulation by the admins, without having to reboot or install
something.
A userspace API is provided which will be used by the applications.

>
> 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);
> >>
> >>
> >

--
Shine bright,
(: Nav :)