linux-kernel - Re: [PATCH] devfreq: Suspend all devices on system shutdown

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Date:   Mon, 28 Jan 2019 10:17:17 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Lukasz Luba <l.luba@...tner.samsung.com>,
        Markus Reichl <m.reichl@...etechno.de>
Subject: Re: [PATCH] devfreq: Suspend all devices on system shutdown

Hi,

On 19. 1. 25. 오후 10:54, Marek Szyprowski wrote:
> This way devfreq core ensures that all its devices will be set to safe
> operation points before reboot operation. There are board on which some
> aggressive power saving operation points are behind the capabilities of
> the bootloader to properly reset the hardware and boot the board. This
> way one can avoid board crash early after reboot.
> 
> Similar pattern is used in CPUfreq subsystem.
> 
> Reported-by: Markus Reichl <m.reichl@...etechno.de>
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> ---
>  drivers/devfreq/devfreq.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 0ae3de76833b..f6aba8344c56 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -23,6 +23,7 @@
>  #include <linux/devfreq.h>
>  #include <linux/workqueue.h>
>  #include <linux/platform_device.h>
> +#include <linux/syscore_ops.h>
>  #include <linux/list.h>
>  #include <linux/printk.h>
>  #include <linux/hrtimer.h>
> @@ -1422,6 +1423,10 @@ static struct attribute *devfreq_attrs[] = {
>  };
>  ATTRIBUTE_GROUPS(devfreq);
>  
> +static struct syscore_ops devfreq_syscore_ops = {
> +	.shutdown = devfreq_suspend,
> +};
> +
>  static int __init devfreq_init(void)
>  {
>  	devfreq_class = class_create(THIS_MODULE, "devfreq");
> @@ -1438,6 +1443,8 @@ static int __init devfreq_init(void)
>  	}
>  	devfreq_class->dev_groups = devfreq_groups;
>  
> +	register_syscore_ops(&devfreq_syscore_ops);
> +
>  	return 0;
>  }
>  subsys_initcall(devfreq_init);
> 

Looks good to me.
Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics