linux-kernel - Re: [PATCH] PM: EM: Fix uninitialized power in em_create_perf

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Message-ID: <1dcc31f7-1ea9-a595-5ab9-9de4d7130f0b@huawei.com>
Date: Mon, 4 Nov 2024 17:19:55 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: Lukasz Luba <lukasz.luba@....com>
CC: <rafael@...nel.org>, <pavel@....cz>, <len.brown@...el.com>,
	<linux-pm@...r.kernel.org>, <daniel.lezcano@...aro.org>,
	<linux-kernel@...r.kernel.org>, <qperret@...gle.com>
Subject: Re: [PATCH] PM: EM: Fix uninitialized power in em_create_perf_table



On 2024/11/4 17:14, Lukasz Luba wrote:
> Hi Jinjie,
> 
> On 11/4/24 09:03, Jinjie Ruan wrote:
>> In em_create_perf_table(), power is uninitialized and passed the pointer
>> to active_power() hook, but the hook function may not assign it and
>> return 0, such as mtk_cpufreq_get_cpu_power(), so the later zero check
>> for
> 
> Please fix the driver. I have checked that function. It must return
> -EINVAL when the 'policy' is not found. We cannot progress with power=0.

Thank you very much! It will be also good to fix the driver.

> 
> 
>> power is not invalid, initialize power to zero to fix it.
>>
>> Cc: stable@...r.kernel.org
>> Fixes: 7d9895c7fbfc ("PM / EM: introduce em_dev_register_perf_domain
>> function")
>> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
>> ---
>>   kernel/power/energy_model.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/power/energy_model.c b/kernel/power/energy_model.c
>> index 927cc55ba0b3..866a3e9c05b2 100644
>> --- a/kernel/power/energy_model.c
>> +++ b/kernel/power/energy_model.c
>> @@ -344,7 +344,7 @@ static int em_create_perf_table(struct device
>> *dev, struct em_perf_domain *pd,
>>                   struct em_data_callback *cb,
>>                   unsigned long flags)
>>   {
>> -    unsigned long power, freq, prev_freq = 0;
>> +    unsigned long power = 0, freq, prev_freq = 0;
>>       int nr_states = pd->nr_perf_states;
>>       int i, ret;
>>   
> 
> 
> This patch proposal is just a workaround.
> 
> When you send a patch to that MTK driver, I can review it for you so
> please add me on CC.
> 
> Regards,
> Lukasz
>