greybus: loopback: compute average stats on demand only

Stop recording and updating the average every time a sample
is recorded.  Instead, compute it from the sum and count only
when it's required.

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

diff --git a/drivers/staging/greybus/loopback.c b/drivers/staging/greybus/loopback.c
index 432eeab..e76f8a7 100644 (file)
--- a/drivers/staging/greybus/loopback.c
+++ b/drivers/staging/greybus/loopback.c
@@ -25,7 +25,6 @@
 struct gb_loopback_stats {
        u32 min;
        u32 max;
-       u64 avg;
        u64 sum;
        u32 count;
 };
@@ -107,7 +106,11 @@ static ssize_t name##_avg_show(struct device *dev,                 \
 {                                                                      \
        struct gb_connection *connection = to_gb_connection(dev);       \
        struct gb_loopback *gb = connection->private;                   \
-       return sprintf(buf, "%llu\n", gb->name.avg);                    \
+       struct gb_loopback_stats *stats = &gb->name;                    \
+       u32 count = stats->count ? stats->count : 1;                    \
+       u64 avg = stats->sum + count / 2;       /* round closest */     \
+       u32 rem = do_div(avg, count);                                   \
+       return sprintf(buf, "%llu.%06u\n", avg, 1000000 * rem / count); \
 }                                                                      \
 static DEVICE_ATTR_RO(name##_avg)
 
@@ -367,8 +370,6 @@ static void gb_loopback_update_stats(struct gb_loopback_stats *stats, u32 val)
                stats->max = val;
        stats->sum += val;
        stats->count++;
-       stats->avg = stats->sum;
-       do_div(stats->avg, stats->count);
 }
 
 static void gb_loopback_requests_update(struct gb_loopback *gb, u32 latency)