Commit 179c0c70 authored by Yaxiong Tian's avatar Yaxiong Tian Committed by Rafael J. Wysocki
Browse files

PM: EM: Fix potential division-by-zero error in em_compute_costs() 



When the device is of a non-CPU type, table[i].performance won't be
initialized in the previous em_init_performance(), resulting in division
by zero when calculating costs in em_compute_costs().

Since the 'cost' algorithm is only used for EAS energy efficiency
calculations and is currently not utilized by other device drivers, we
should add the _is_cpu_device(dev) check to prevent this division-by-zero
issue.

Fixes: 1b600da5 ("PM: EM: Optimize em_cpu_energy() and remove division")
Signed-off-by: default avatarYaxiong Tian <tianyaxiong@kylinos.cn>
Reviewed-by: default avatarLukasz Luba <lukasz.luba@arm.com>
Link: https://patch.msgid.link/tencent_7F99ED4767C1AF7889D0D8AD50F34859CE06@qq.com


Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent b4432656

kernel/power/energy_model.c

+4 −0
Original line number Diff line number Diff line
@@ -233,6 +233,10 @@ static int em_compute_costs(struct device *dev, struct em_perf_state *table, 
	unsigned long prev_cost = ULONG_MAX;

	int i, ret;



	/* This is needed only for CPUs and EAS skip other devices */

	if (!_is_cpu_device(dev))

		return 0;



	/* Compute the cost of each performance state. */

	for (i = nr_states - 1; i >= 0; i--) {

		unsigned long power_res, cost;