linux-kernel - [PATCH] thermal: power_allocator: using round the division when re-divvying up power

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Message-Id: <1615796737-4688-1-git-send-email-gao.yunxiao6@gmail.com>
Date:   Mon, 15 Mar 2021 16:25:37 +0800
From:   gao.yunxiao6@...il.com
To:     lukasz.luba@....com, rui.zhang@...el.com,
        daniel.lezcano@...aro.org, amitk@...nel.org
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        orsonzhai@...il.com, zhang.lyra@...il.com,
        "jeson.gao" <jeson.gao@...soc.com>
Subject: [PATCH] thermal: power_allocator: using round the division when re-divvying up power

From: "jeson.gao" <jeson.gao@...soc.com>

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 it's max_power, it has the extra_power 759
actor1 received less than it's max_power, it require extra_actor_power 395
actor2 received less than it's 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@...soc.com>
---
 drivers/thermal/gov_power_allocator.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/thermal/gov_power_allocator.c b/drivers/thermal/gov_power_allocator.c
index 92acae53df49..2802a0e13c88 100644
--- 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,
-- 
2.28.0