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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>
This commit is contained in:
Javi Merino 2015-05-02 10:15:24 +01:00 committed by Eduardo Valentin
parent 488c7455d7
commit ea54cac906
1 changed files with 2 additions and 1 deletions
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3
drivers/thermal/power_allocator.c
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@ -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++) { for (i = 0; i < num_actors; i++) {
u64 req_range = req_power[i] * power_range; 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]) { if (granted_power[i] > max_power[i]) {
extra_power += granted_power[i] - max_power[i]; extra_power += granted_power[i] - max_power[i];