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Date: Thu, 9 May 2019 10:38:38 -0500
From: Eddie James <eajames@...ux.vnet.ibm.com>
To: Guenter Roeck <linux@...ck-us.net>,
Eddie James <eajames@...ux.ibm.com>
Cc: linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
jdelvare@...e.com
Subject: Re: [PATCH] hwmon (occ): Switch power average to between poll
responses
On 5/8/19 4:03 PM, Guenter Roeck wrote:
> On Tue, May 07, 2019 at 02:35:51PM -0500, Eddie James wrote:
>> The average power reported in the hwmon OCC driver is not useful
>> because the time it represents is too short. Instead, store the
>> previous power accumulator reported by the OCC and average it with the
>> latest accumulator to obtain an average between poll responses. This
>> does operate under the assumption that the user polls regularly.
>>
> That looks really bad. Effectively it means that the number reported
> as average power is more or less useless/random. On top of that, the code
> gets so complicated that it is all but impossible to understand.
>
> Does it really make sense to report an average that has effectively
> no useful meaning (and is, for example, influenced just by reading it) ?
Yea... that's a good point. Basically our userspace environment has no
good way to do this either, so I tried to shoe-horn this into the
driver, but this approach is indeed bad. I'll abandon this patch.
Thanks!
Eddie
>
> Guenter
>
>> Signed-off-by: Eddie James <eajames@...ux.ibm.com>
>> ---
>> drivers/hwmon/occ/common.c | 133 ++++++++++++++++++++++++++++++++-------------
>> drivers/hwmon/occ/common.h | 7 +++
>> 2 files changed, 103 insertions(+), 37 deletions(-)
>>
>> diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
>> index e6d3fb5..6ffcee7 100644
>> --- a/drivers/hwmon/occ/common.c
>> +++ b/drivers/hwmon/occ/common.c
>> @@ -118,6 +118,53 @@ struct extended_sensor {
>> u8 data[6];
>> } __packed;
>>
>> +static void occ_update_prev_power_avgs(struct occ *occ)
>> +{
>> + u8 i;
>> + struct power_sensor_1 *ps1;
>> + struct power_sensor_2 *ps2;
>> + struct power_sensor_a0 *psa0;
>> + struct occ_sensor *power = &occ->sensors.power;
>> + struct occ_power_avg *prevs = occ->prev_power_avgs;
>> +
>> + switch (power->version) {
>> + case 1:
>> + for (i = 0; i < power->num_sensors; ++i) {
>> + ps1 = ((struct power_sensor_1 *)power->data) + i;
>> +
>> + prevs[i].accumulator =
>> + get_unaligned_be32(&ps1->accumulator);
>> + prevs[i].update_tag =
>> + get_unaligned_be32(&ps1->update_tag);
>> + }
>> + break;
>> + case 2:
>> + for (i = 0; i < power->num_sensors; ++i) {
>> + ps2 = ((struct power_sensor_2 *)power->data) + i;
>> +
>> + prevs[i].accumulator =
>> + get_unaligned_be64(&ps2->accumulator);
>> + prevs[i].update_tag =
>> + get_unaligned_be32(&ps2->update_tag);
>> + }
>> + break;
>> + case 0xA0:
>> + for (i = 0; i < power->num_sensors; ++i) {
>> + psa0 = ((struct power_sensor_a0 *)power->data) + i;
>> +
>> + prevs[i].accumulator = psa0->system.accumulator;
>> + prevs[i].update_tag = psa0->system.update_tag;
>> + prevs[i + 1].accumulator = psa0->proc.accumulator;
>> + prevs[i + 1].update_tag = psa0->proc.update_tag;
>> + prevs[i + 2].accumulator = psa0->vdd.accumulator;
>> + prevs[i + 2].update_tag = psa0->vdd.update_tag;
>> + prevs[i + 3].accumulator = psa0->vdn.accumulator;
>> + prevs[i + 3].update_tag = psa0->vdn.update_tag;
>> + }
>> + break;
>> + }
>> +}
>> +
>> static int occ_poll(struct occ *occ)
>> {
>> int rc;
>> @@ -135,6 +182,8 @@ static int occ_poll(struct occ *occ)
>> cmd[6] = checksum & 0xFF; /* checksum lsb */
>> cmd[7] = 0;
>>
>> + occ_update_prev_power_avgs(occ);
>> +
>> /* mutex should already be locked if necessary */
>> rc = occ->send_cmd(occ, cmd);
>> if (rc) {
>> @@ -208,6 +257,7 @@ int occ_update_response(struct occ *occ)
>> /* limit the maximum rate of polling the OCC */
>> if (time_after(jiffies, occ->last_update + OCC_UPDATE_FREQUENCY)) {
>> rc = occ_poll(occ);
>> + occ->prev_update = occ->last_update;
>> occ->last_update = jiffies;
>> } else {
>> rc = occ->last_error;
>> @@ -364,6 +414,14 @@ static ssize_t occ_show_freq_2(struct device *dev,
>> return snprintf(buf, PAGE_SIZE - 1, "%u\n", val);
>> }
>>
>> +static u64 occ_power_avg(struct occ *occ, u8 idx, u64 accum, u32 samples)
>> +{
>> + struct occ_power_avg *avg = &occ->prev_power_avgs[idx];
>> +
>> + return div_u64((accum - avg->accumulator) * 1000000ULL,
>> + samples - avg->update_tag);
>> +}
>> +
>> static ssize_t occ_show_power_1(struct device *dev,
>> struct device_attribute *attr, char *buf)
>> {
>> @@ -385,13 +443,12 @@ static ssize_t occ_show_power_1(struct device *dev,
>> val = get_unaligned_be16(&power->sensor_id);
>> break;
>> case 1:
>> - val = get_unaligned_be32(&power->accumulator) /
>> - get_unaligned_be32(&power->update_tag);
>> - val *= 1000000ULL;
>> + val = occ_power_avg(occ, sattr->index,
>> + get_unaligned_be32(&power->accumulator),
>> + get_unaligned_be32(&power->update_tag));
>> break;
>> case 2:
>> - val = (u64)get_unaligned_be32(&power->update_tag) *
>> - occ->powr_sample_time_us;
>> + val = jiffies_to_usecs(occ->last_update - occ->prev_update);
>> break;
>> case 3:
>> val = get_unaligned_be16(&power->value) * 1000000ULL;
>> @@ -403,12 +460,6 @@ static ssize_t occ_show_power_1(struct device *dev,
>> return snprintf(buf, PAGE_SIZE - 1, "%llu\n", val);
>> }
>>
>> -static u64 occ_get_powr_avg(u64 *accum, u32 *samples)
>> -{
>> - return div64_u64(get_unaligned_be64(accum) * 1000000ULL,
>> - get_unaligned_be32(samples));
>> -}
>> -
>> static ssize_t occ_show_power_2(struct device *dev,
>> struct device_attribute *attr, char *buf)
>> {
>> @@ -431,12 +482,12 @@ static ssize_t occ_show_power_2(struct device *dev,
>> get_unaligned_be32(&power->sensor_id),
>> power->function_id, power->apss_channel);
>> case 1:
>> - val = occ_get_powr_avg(&power->accumulator,
>> - &power->update_tag);
>> + val = occ_power_avg(occ, sattr->index,
>> + get_unaligned_be64(&power->accumulator),
>> + get_unaligned_be32(&power->update_tag));
>> break;
>> case 2:
>> - val = (u64)get_unaligned_be32(&power->update_tag) *
>> - occ->powr_sample_time_us;
>> + val = jiffies_to_usecs(occ->last_update - occ->prev_update);
>> break;
>> case 3:
>> val = get_unaligned_be16(&power->value) * 1000000ULL;
>> @@ -452,6 +503,8 @@ static ssize_t occ_show_power_a0(struct device *dev,
>> struct device_attribute *attr, char *buf)
>> {
>> int rc;
>> + u32 samples;
>> + u64 accum;
>> u64 val = 0;
>> struct power_sensor_a0 *power;
>> struct occ *occ = dev_get_drvdata(dev);
>> @@ -469,12 +522,15 @@ static ssize_t occ_show_power_a0(struct device *dev,
>> return snprintf(buf, PAGE_SIZE - 1, "%u_system\n",
>> get_unaligned_be32(&power->sensor_id));
>> case 1:
>> - val = occ_get_powr_avg(&power->system.accumulator,
>> - &power->system.update_tag);
>> + accum = get_unaligned_be64(&power->system.accumulator);
>> + samples = get_unaligned_be32(&power->system.update_tag);
>> + val = occ_power_avg(occ, sattr->index, accum, samples);
>> break;
>> case 2:
>> - val = (u64)get_unaligned_be32(&power->system.update_tag) *
>> - occ->powr_sample_time_us;
>> + case 6:
>> + case 10:
>> + case 14:
>> + val = jiffies_to_usecs(occ->last_update - occ->prev_update);
>> break;
>> case 3:
>> val = get_unaligned_be16(&power->system.value) * 1000000ULL;
>> @@ -483,12 +539,9 @@ static ssize_t occ_show_power_a0(struct device *dev,
>> return snprintf(buf, PAGE_SIZE - 1, "%u_proc\n",
>> get_unaligned_be32(&power->sensor_id));
>> case 5:
>> - val = occ_get_powr_avg(&power->proc.accumulator,
>> - &power->proc.update_tag);
>> - break;
>> - case 6:
>> - val = (u64)get_unaligned_be32(&power->proc.update_tag) *
>> - occ->powr_sample_time_us;
>> + accum = get_unaligned_be64(&power->proc.accumulator);
>> + samples = get_unaligned_be32(&power->proc.update_tag);
>> + val = occ_power_avg(occ, sattr->index + 1, accum, samples);
>> break;
>> case 7:
>> val = get_unaligned_be16(&power->proc.value) * 1000000ULL;
>> @@ -497,12 +550,9 @@ static ssize_t occ_show_power_a0(struct device *dev,
>> return snprintf(buf, PAGE_SIZE - 1, "%u_vdd\n",
>> get_unaligned_be32(&power->sensor_id));
>> case 9:
>> - val = occ_get_powr_avg(&power->vdd.accumulator,
>> - &power->vdd.update_tag);
>> - break;
>> - case 10:
>> - val = (u64)get_unaligned_be32(&power->vdd.update_tag) *
>> - occ->powr_sample_time_us;
>> + accum = get_unaligned_be64(&power->vdd.accumulator);
>> + samples = get_unaligned_be32(&power->vdd.update_tag);
>> + val = occ_power_avg(occ, sattr->index + 2, accum, samples);
>> break;
>> case 11:
>> val = get_unaligned_be16(&power->vdd.value) * 1000000ULL;
>> @@ -511,12 +561,9 @@ static ssize_t occ_show_power_a0(struct device *dev,
>> return snprintf(buf, PAGE_SIZE - 1, "%u_vdn\n",
>> get_unaligned_be32(&power->sensor_id));
>> case 13:
>> - val = occ_get_powr_avg(&power->vdn.accumulator,
>> - &power->vdn.update_tag);
>> - break;
>> - case 14:
>> - val = (u64)get_unaligned_be32(&power->vdn.update_tag) *
>> - occ->powr_sample_time_us;
>> + accum = get_unaligned_be64(&power->vdn.accumulator);
>> + samples = get_unaligned_be32(&power->vdn.update_tag);
>> + val = occ_power_avg(occ, sattr->index + 3, accum, samples);
>> break;
>> case 15:
>> val = get_unaligned_be16(&power->vdn.value) * 1000000ULL;
>> @@ -719,6 +766,7 @@ static ssize_t occ_show_extended(struct device *dev,
>> static int occ_setup_sensor_attrs(struct occ *occ)
>> {
>> unsigned int i, s, num_attrs = 0;
>> + unsigned int power_avgs_size = 0;
>> struct device *dev = occ->bus_dev;
>> struct occ_sensors *sensors = &occ->sensors;
>> struct occ_attribute *attr;
>> @@ -761,9 +809,13 @@ static int occ_setup_sensor_attrs(struct occ *occ)
>> /* fall through */
>> case 1:
>> num_attrs += (sensors->power.num_sensors * 4);
>> + power_avgs_size = sizeof(struct occ_power_avg) *
>> + sensors->power.num_sensors;
>> break;
>> case 0xA0:
>> num_attrs += (sensors->power.num_sensors * 16);
>> + power_avgs_size = sizeof(struct occ_power_avg) *
>> + sensors->power.num_sensors * 4;
>> show_power = occ_show_power_a0;
>> break;
>> default:
>> @@ -792,6 +844,13 @@ static int occ_setup_sensor_attrs(struct occ *occ)
>> sensors->extended.num_sensors = 0;
>> }
>>
>> + if (power_avgs_size) {
>> + occ->prev_power_avgs = devm_kzalloc(dev, power_avgs_size,
>> + GFP_KERNEL);
>> + if (!occ->prev_power_avgs)
>> + return -ENOMEM;
>> + }
>> +
>> occ->attrs = devm_kzalloc(dev, sizeof(*occ->attrs) * num_attrs,
>> GFP_KERNEL);
>> if (!occ->attrs)
>> diff --git a/drivers/hwmon/occ/common.h b/drivers/hwmon/occ/common.h
>> index c676e48..08970f8 100644
>> --- a/drivers/hwmon/occ/common.h
>> +++ b/drivers/hwmon/occ/common.h
>> @@ -87,17 +87,24 @@ struct occ_attribute {
>> struct sensor_device_attribute_2 sensor;
>> };
>>
>> +struct occ_power_avg {
>> + u64 accumulator;
>> + u32 update_tag;
>> +};
>> +
>> struct occ {
>> struct device *bus_dev;
>>
>> struct occ_response resp;
>> struct occ_sensors sensors;
>> + struct occ_power_avg *prev_power_avgs;
>>
>> int powr_sample_time_us; /* average power sample time */
>> u8 poll_cmd_data; /* to perform OCC poll command */
>> int (*send_cmd)(struct occ *occ, u8 *cmd);
>>
>> unsigned long last_update;
>> + unsigned long prev_update;
>> struct mutex lock; /* lock OCC access */
>>
>> struct device *hwmon;
>> --
>> 1.8.3.1
>>
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