linux-kernel - Re: [PATCH v3 1/5] powercap/drivers/dtpm: Encapsulate even more the code

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Date:   Thu, 11 Mar 2021 10:15:19 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     rafael@...nel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v3 1/5] powercap/drivers/dtpm: Encapsulate even more the
 code

Hi Daniel,

On 3/10/21 11:02 AM, Daniel Lezcano wrote:
> In order to increase the self-encapsulation of the dtpm generic code,
> the following changes are adding a power update ops to the dtpm
> ops. That allows the generic code to call directly the dtpm backend
> function to update the power values.
> 
> The power update function does compute the power characteristics when
> the function is invoked. In the case of the CPUs, the power
> consumption depends on the number of online CPUs. The online CPUs mask
> is not up to date at CPUHP_AP_ONLINE_DYN state in the tear down
> callback. That is the reason why the online / offline are at separate
> state. As there is already an existing state for DTPM, this one is
> only moved to the DEAD state, so there is no addition of new state
> with these changes. The dtpm node is not removed when the cpu is
> unplugged.
> 
> That simplifies the code for the next changes and results in a more
> self-encapsulated code.
> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
> V2:
>   - Updated the changelog with the CPU node not being removed
>   - Commented the cpu hotplug callbacks to explain why there are two callbacks
>   - Changed 'upt_power_uw' to 'update_power_uw'
>   - Removed unused cpumask variable
> ---
>   drivers/powercap/dtpm.c     |  54 ++++++-------
>   drivers/powercap/dtpm_cpu.c | 148 ++++++++++++++++--------------------
>   include/linux/cpuhotplug.h  |   2 +-
>   include/linux/dtpm.h        |   3 +-
>   4 files changed, 97 insertions(+), 110 deletions(-)
> 

[snip]

> @@ -210,27 +175,20 @@ static int cpuhp_dtpm_cpu_online(unsigned int cpu)
>   	for_each_cpu(cpu, policy->related_cpus)
>   		per_cpu(dtpm_per_cpu, cpu) = dtpm;
>   
> -	sprintf(name, "cpu%d", dtpm_cpu->cpu);
> +	sprintf(name, "cpu%d-cpufreq", dtpm_cpu->cpu);

We should be safe in normal platforms, since there is less than
< 300 cores. although, I would use 2x CPUFREQ_NAME_LEN array.

Other than that

Reviewed-by: Lukasz Luba <lukasz.luba@....com>

Regards,
Lukasz