Currently, all sensors are read when the energy meter is queried via sysfs.
This introduces a considerable amount of delay and variation in the sysfs
reading, which is not desirable when trying to profile energy use. Therefore,
read only the energy meters when a sysfs query comes in for them, and don't
cache the results so that we always get the latest reading.

Signed-off-by: Darrick J. Wong
---

drivers/hwmon/ibmaem.c | 18 +++++++++++++-----
1 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/hwmon/ibmaem.c b/drivers/hwmon/ibmaem.c
index c9416e6..f660216 100644
--- a/drivers/hwmon/ibmaem.c
+++ b/drivers/hwmon/ibmaem.c
@@ -463,12 +463,18 @@ static int aem_read_sensor(struct aem_data *data, u8 elt, u8 reg,
}

/* Update AEM energy registers */
+static void update_aem_energy_one(struct aem_data *data, int which)
+{
+ aem_read_sensor(data, AEM_ENERGY_ELEMENT, which,
+ &data->energy[which], 8);
+}
+
static void update_aem_energy(struct aem_data *data)
{
- aem_read_sensor(data, AEM_ENERGY_ELEMENT, 0, &data->energy[0], 8);
+ update_aem_energy_one(data, 0);
if (data->ver_major < 2)
return;
- aem_read_sensor(data, AEM_ENERGY_ELEMENT, 1, &data->energy[1], 8);
+ update_aem_energy_one(data, 1);
}

/* Update all AEM1 sensors */
@@ -849,7 +855,7 @@ static ssize_t aem_show_power(struct device *dev,
struct timespec b, a;

mutex_lock(&data->lock);
- update_aem_energy(data);
+ update_aem_energy_one(data, attr->index);
getnstimeofday(&b);
before = data->energy[attr->index];

@@ -861,7 +867,7 @@ static ssize_t aem_show_power(struct device *dev,
return 0;
}

- update_aem_energy(data);
+ update_aem_energy_one(data, attr->index);
getnstimeofday(&a);
after = data->energy[attr->index];
mutex_unlock(&data->lock);
@@ -880,7 +886,9 @@ static ssize_t aem_show_energy(struct device *dev,
{
struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
struct aem_data *a = dev_get_drvdata(dev);
- a->update(a);
+ mutex_lock(&a->lock);
+ update_aem_energy_one(a, attr->index);
+ mutex_unlock(&a->lock);

return sprintf(buf, "%llu\n",
(unsigned long long)a->energy[attr->index] * 1000);
--
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