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Date:   Thu, 11 Nov 2021 12:28:07 +0800
From:   Youquan Song <youquan.song@linux.intel.com>
To:     "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc:     Youquan Song <youquan.song@linux.intel.com>,
        linux-pm@vger.kernel.org, youquan.song@intel.com
Subject: Re: [PATCH] PM/QoS: resume latency 0 should be not latency allowed
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On Wed, Nov 10, 2021 at 08:24:12PM +0100, Rafael J. Wysocki wrote:
> On 11/10/2021 11:58 AM, Youquan Song wrote:
> >>But do you really need to make these changes?  What problem is there with using the interface as currently documented, ie. writing "n/a" to it to get "no latency at all"?
> >I think so. "0" is "latency is not allowed", but "n/a" is "no latency".
> >
> Actually, "0" means "I don't care" and "n/a" means "no latency"
> which means latency tolerance == 0.
So it is not reasonable and need change. "0" is the smallest latency and means "latency not allowed"; if latency_req==0, it will not allow to enter into C-state. "n/a" is largest latency and means "I don't care" the input of latency_req at all.