thermal/core/power_allocator: Using round the division when re-divvying up power

The division is used directly in re-divvying up power, the decimal part will
be discarded, devices will get less than the extra_actor_power - 1.
if using round the division to make the calculation more accurate.

For example:
actor0 received more than its max_power, it has the extra_power 759
actor1 received less than its max_power, it require extra_actor_power 395
actor2 received less than its max_power, it require extra_actor_power 365
actor1 and actor2 require the total capped_extra_power 760

using division in re-divvying up power
actor1 would actually get the extra_actor_power 394
actor2 would actually get the extra_actor_power 364

if using round the division in re-divvying up power
actor1 would actually get the extra_actor_power 394
actor2 would actually get the extra_actor_power 365

Signed-off-by: Jeson Gao <jeson.gao@unisoc.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/1615796737-4688-1-git-send-email-gao.yunxiao6@gmail.com

diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
index 92acae5..2802a0e 100644 (file)
--- a/drivers/thermal/gov_power_allocator.c
+++ b/drivers/thermal/gov_power_allocator.c
@@ -374,9 +374,11 @@ static void divvy_up_power(u32 *req_power, u32 *max_power, int num_actors,
         */
        extra_power = min(extra_power, capped_extra_power);
        if (capped_extra_power > 0)
-               for (i = 0; i < num_actors; i++)
-                       granted_power[i] += (extra_actor_power[i] *
-                                       extra_power) / capped_extra_power;
+               for (i = 0; i < num_actors; i++) {
+                       u64 extra_range = (u64)extra_actor_power[i] * extra_power;
+                       granted_power[i] += DIV_ROUND_CLOSEST_ULL(extra_range,
+                                                        capped_extra_power);
+               }
 }
 
 static int allocate_power(struct thermal_zone_device *tz,