ibmaem: don't query the entire sensor repository when reading energy meter

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 <djwong@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 5 deletions

diff --git a/drivers/hwmon/ibmaem.c b/drivers/hwmon/ibmaem.c
index 08c5179e6d84..0f70dc204105 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 */
@@ -850,7 +856,7 @@ 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];
 
@@ -862,7 +868,7 @@ 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);
@@ -881,7 +887,9 @@ 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);