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

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[ Upstream commit 179c0c7044a378198adb36f2a12410ab68cc730a ]

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: 1b600da510 ("PM: EM: Optimize em_cpu_energy() and remove division")
Signed-off-by: Yaxiong Tian <tianyaxiong@kylinos.cn>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://patch.msgid.link/tencent_7F99ED4767C1AF7889D0D8AD50F34859CE06@qq.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Yaxiong Tian
2025-04-18 09:06:13 +08:00
committed by Greg Kroah-Hartman
parent d05c33c14f
commit 81d72f9241
1 changed files with 4 additions and 0 deletions
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4
kernel/power/energy_model.c
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@@ -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;