linux-kernel - Re: [PATCH v3] PM / QoS: add pm_qos_update_request

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Date:	Sun, 25 Mar 2012 20:02:39 -0700
From:	mark gross <markgross@...gnar.org>
To:	myungjoo.ham@...il.com
Cc:	markgross@...gnar.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	linux-pm@...r.kernel.org, Len Brown <len.brown@...el.com>,
	Pavel Machek <pavel@....cz>, Kevin Hilman <khilman@...com>,
	Jean Pihet <j-pihet@...com>, kyungmin.park@...sung.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] PM / QoS: add pm_qos_update_request_timeout API

On Mon, Mar 26, 2012 at 10:41:15AM +0900, MyungJoo Ham wrote:
> On Sun, Mar 25, 2012 at 1:35 AM, mark gross <markgross@...gnar.org> wrote:
> > I apologize for the lat replay and admit that I was probably wrong to
> > oppose the idea of time out pm_qos requests.  (last week we bumped into
> > a need for them and now I get it.)
> >
> >
> > On Wed, Mar 07, 2012 at 02:06:18PM +0900, MyungJoo Ham wrote:
> >> The new API, pm_qos_update_request_timeout() is to provide a timeout
> >> with pm_qos_update_request.
> >>
> >> For example, pm_qos_update_request_timeout(req, 100, 1000), means that
> >> QoS request on req with value 100 will be active for 1000 jiffies.
> >> After 1000 jiffies, the QoS request thru req is rolled back to the
> >> request status when pm_qos_update_request_timeout() was called. If there
> >> were another pm_qos_update_request(req, x) during the 1000 jiffies, this
> >> new request with value x will override as this is another request on the
> >> same req handle. A new request on the same req handle will always
> >> override the previous request whether it is the conventional request or
> >> it is the new timeout request.
> >>
> >> Signed-off-by: MyungJoo Ham <myungjoo.ham@...sung.com>
> >> Signed-off-by: Kyungmin Park <kyungmin.park@...sung.com>
> []
> >> @@ -77,6 +79,8 @@ void pm_qos_add_request(struct pm_qos_request *req, int pm_qos_class,
> >>                       s32 value);
> >>  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_ms);
> > is ms the right units?  could we ever need us?
> >
> 
> Because jiffies are used for scheduling tasks, I thought ms should be
> fine and having some devices running fast for some msecs longer won't
> hurt. However, do you expect scheduling tasks or jiffies may use usecs
> later? I don't mind using usecs instead of msecs here; thus, I'll
> update this to use usecs. I'll resend patchset soon.
> 

I am just asking a question.  I'm not sure if us or ms are the better
units off the top of my head.

--mark

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