Commit babef976 authored May 02, 2015 by Javi Merino Committed by Kevin Hilman Jun 05, 2015

thermal: power_allocator: round the division when divvying up power



In situations where there is an uneven number of cooling devices, the
division of power among them can lead to a milliwatt being dropped on
the floor due to rounding errors.  This doesn't sound like a lot, but
some devices only grant the lowest cooling device state for their
maximum power.  So for instance, if the granted_power is the maximum
power and all devices are getting their maximum power, one would get
max_power - 1, making it choose cooling device state 1, instead of 0.

Round the division to make the calculation more accurate.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
(cherry picked from commit ea54cac9065112724f3432e0574ba3e346fd695d)
Signed-off-by: Kevin Hilman <khilman@linaro.org>

parent 22793eb9

drivers/thermal/power_allocator.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -196,7 +196,8 @@ static void divvy_up_power(u32 req_power, u32 max_power, int num_actors,
		for (i = 0; i < num_actors; i++) {
		u64 req_range = req_power[i] * power_range;

		granted_power[i] = div_u64(req_range, total_req_power);
		granted_power[i] = DIV_ROUND_CLOSEST_ULL(req_range,
		total_req_power);

		if (granted_power[i] > max_power[i]) {
		extra_power += granted_power[i] - max_power[i];