linux-kernel - Re: [PATCH 2/4] cpu: expose pm_qos_resume

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Date:   Tue, 13 Sep 2016 21:57:28 +0800
From:   Alex Shi <alex.shi@...aro.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Cc:     linux-pm@...r.kernel.org, Ulf Hansson <ulf.hansson@...aro.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH 2/4] cpu: expose pm_qos_resume_latency for each cpu

Cc Rafael,

This patchset is quit simple and straight. Is there any concern or
hesitate on it?

Thanks
Alex

On 09/01/2016 11:50 AM, Alex Shi wrote:
> 
> Few commits and patch changed according to Greg's comments.
> 
> Regards
> Alex
> 
> ====
> 
> From 186c534b0b8b9649fbfce05b0b4f90f764c571a4 Mon Sep 17 00:00:00 2001
> From: Alex Shi <alex.shi@...aro.org>
> Date: Tue, 16 Aug 2016 15:29:01 +0800
> Subject: [PATCH 2/4] cpu: expose pm_qos_resume_latency for each cpu
> 
> Adding /sys/devices/system/cpu/cpux/power/pm_qos_resume_latency_us for
> each of cpus. The pm_qos_resume_latency usage defined in
> Documentation/ABI/testing/sysfs-devices-power
> 
> The cpu-dma PM QoS constraint impacts all the cpus in the system. There
> is no way to let the user to choose a PM QoS constraint per cpu.
> 
> The following patch exposes to the userspace a per cpu based sysfs file
> in order to let the userspace to change the value of the PM QoS latency
> constraint.
> 
> This change is inoperative in its form and the cpuidle governors have to
> take into account the per cpu latency constraint in addition to the
> global cpu-dma latency constraint in order to operate properly.
> 
> Signed-off-by: Alex Shi <alex.shi@...aro.org>
> To: linux-kernel@...r.kernel.org
> To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: linux-pm@...r.kernel.org
> Cc: Ulf Hansson <ulf.hansson@...aro.org>
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
>  drivers/base/cpu.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> index 4c28e1a..2c3b359 100644
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -17,6 +17,7 @@
>  #include <linux/of.h>
>  #include <linux/cpufeature.h>
>  #include <linux/tick.h>
> +#include <linux/pm_qos.h>
>  
>  #include "base.h"
>  
> @@ -376,6 +377,7 @@ int register_cpu(struct cpu *cpu, int num)
>  
>  	per_cpu(cpu_sys_devices, num) = &cpu->dev;
>  	register_cpu_under_node(num, cpu_to_node(num));
> +	dev_pm_qos_expose_latency_limit(&cpu->dev, 0);
>  
>  	return 0;
>  }
>