linux-kernel - Re: [RFC PATCH 1/4] PM / QoS: Add pm_qos_cancel_request

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Date:	Mon, 20 Apr 2015 14:00:35 -0000
From:	"Dov Levenglick" <dovl@...eaurora.org>
To:	"Adrian Hunter" <adrian.hunter@...el.com>
Cc:	"Ulf Hansson" <ulf.hansson@...aro.org>,
	"linux-mmc" <linux-mmc@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"Len Brown" <len.brown@...el.com>, "Pavel Machek" <pavel@....cz>,
	"Kevin Hilman" <khilman@...aro.org>,
	"Tomeu Vizoso" <tomeu.vizoso@...labora.com>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/4] PM / QoS: Add pm_qos_cancel_request_lazy() that
 doesn't sleep

> Add pm_qos_cancel_request_lazy() which is convenient for
> contexts that may not sleep.
>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>  include/linux/pm_qos.h |  2 ++
>  kernel/power/qos.c     | 20 ++++++++++++++++++++
>  2 files changed, 22 insertions(+)
>
> diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
> index 7b3ae0c..f44d353 100644
> --- a/include/linux/pm_qos.h
> +++ b/include/linux/pm_qos.h
> @@ -126,6 +126,8 @@ void pm_qos_update_request(struct pm_qos_request *req,
>  			   s32 new_value);
>  void pm_qos_update_request_timeout(struct pm_qos_request *req,
>  				   s32 new_value, unsigned long
> timeout_us);
> +void pm_qos_cancel_request_lazy(struct pm_qos_request *req,
> +				unsigned int timeout_us);
>  void pm_qos_remove_request(struct pm_qos_request *req);
>

I think that this could be acheived using existing API if
pm_qos_update_request_timeout() were to be called with the existing
timeout value.
Since reading the existing timeout value is missing - and I think would be
a useful feature to have for other use-cases - do you agree with such an
approach?

>  int pm_qos_request(int pm_qos_class);
> diff --git a/kernel/power/qos.c b/kernel/power/qos.c
> index 97b0df7..ac131cb 100644
> --- a/kernel/power/qos.c
> +++ b/kernel/power/qos.c
> @@ -517,6 +517,26 @@ void pm_qos_update_request_timeout(struct
> pm_qos_request *req, s32 new_value,
>  }
>
>  /**
> + * pm_qos_cancel_request_lazy - cancels an existing qos request lazily.
> + * @req : handle to list element holding a pm_qos request to use
> + * @timeout_us: the delay before cancelling this qos request in usecs.
> + *
> + * After timeout_us, this qos request is cancelled.
> + */
> +void pm_qos_cancel_request_lazy(struct pm_qos_request *req,
> +				unsigned int timeout_us)
> +{
> +	if (!req)
> +		return;
> +	if (WARN(!pm_qos_request_active(req),
> +		 "%s called for unknown object.", __func__))
> +		return;
> +
> +	schedule_delayed_work(&req->work, usecs_to_jiffies(timeout_us));
> +}
> +EXPORT_SYMBOL_GPL(pm_qos_cancel_request_lazy);
> +
> +/**
>   * pm_qos_remove_request - modifies an existing qos request
>   * @req: handle to request list element
>   *
> --
> 1.9.1
>
> --
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>


QUALCOMM ISRAEL, on behalf of Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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