From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Kamble, Sagar A" Subject: Re: Why idle_freq is set to RPn and not RPe Date: Wed, 30 Dec 2015 16:09:46 +0530 Message-ID: <5683B472.1000309@intel.com> References: <5683A217.4000806@intel.com> <20151230093112.GU31221@nuc-i3427.alporthouse.com> <17D64081036A3D43BA31B5EA9AE8F54A4676DF7F@IRSMSX108.ger.corp.intel.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0891427676==" Return-path: Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by gabe.freedesktop.org (Postfix) with ESMTP id B583C6E0B2 for ; Wed, 30 Dec 2015 02:39:51 -0800 (PST) In-Reply-To: <17D64081036A3D43BA31B5EA9AE8F54A4676DF7F@IRSMSX108.ger.corp.intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: "Szwichtenberg, Radoslaw" , Chris Wilson Cc: "S, Deepak" , Intel Graphics Development , "Goel, Akash" List-Id: intel-gfx@lists.freedesktop.org This is a multi-part message in MIME format. --===============0891427676== Content-Type: multipart/alternative; boundary="------------000101040503030706080808" This is a multi-part message in MIME format. --------------000101040503030706080808 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Turbo frequency range is Rpe to Rp0 when GPU is active as, on workload submission frequency is taken to Rpe. Does the HW require us to drop to RPn before entering RC6? If we can enter RC6 even with other frequencies I think we can keep running at Rpe on Idle. Only benefit of running at Rpn might be some additional power saving when workload is very lightweight. Is that correct Chris? Thanks Sagar On 12/30/2015 3:20 PM, Szwichtenberg, Radoslaw wrote: > Hello Chris! > > The question is: why this change in behavior was made? > > On previous platforms Gfx Turbo frequency selection range in driver was in between Rpe & Rp0. Since Rpe is the possible Fmax at Vmin, it was used as the starting frequency once driver booted and any value lower than that was not requested. > > Thanks! > Radek > >> -----Original Message----- >> From: Chris Wilson [mailto:chris@chris-wilson.co.uk] >> Sent: Wednesday, December 30, 2015 10:31 AM >> To: Kamble, Sagar A >> Cc: S, Deepak; Szwichtenberg, Radoslaw; Intel Graphics Development; Goel, >> Akash >> Subject: Re: Why idle_freq is set to RPn and not RPe >> >> On Wed, Dec 30, 2015 at 02:51:27PM +0530, Kamble, Sagar A wrote: >>> Hi Chris, >>> >>> With below commit, idle frequency is made RPn (HW Min). >>> Why are we not keeping it at RPe (Efficient Frequency)? >>> My understanding was to set Rpe on idle so that when GPU is out of >>> RC6 it can start operating at efficient frequency. >> The driver is *idle*. When there is work to be submitted to the GPU, then >> we go back to RPe (though we wait for it to wake up first). RPe is just an >> inflexion point on the power curve. >> -Chris >> >> -- >> Chris Wilson, Intel Open Source Technology Centre --------------000101040503030706080808 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: 7bit

Turbo frequency range is Rpe to Rp0 when GPU is active as, on workload submission frequency is taken to Rpe.

Does the HW require us to drop to RPn before entering RC6?
If we can enter RC6 even with other frequencies I think we can keep running at Rpe on Idle.

Only benefit of running at Rpn might be some additional power saving when workload is very lightweight. Is that correct Chris?

Thanks
Sagar

On 12/30/2015 3:20 PM, Szwichtenberg, Radoslaw wrote:

Hello Chris!

The question is: why this change in behavior was made? 

On previous platforms Gfx Turbo frequency selection range in driver was in between Rpe & Rp0. Since Rpe is the possible Fmax at Vmin, it was used as the starting frequency once driver booted and any value lower than that was not requested.

Thanks!
Radek

-----Original Message-----
From: Chris Wilson [mailto:chris@chris-wilson.co.uk]
Sent: Wednesday, December 30, 2015 10:31 AM
To: Kamble, Sagar A
Cc: S, Deepak; Szwichtenberg, Radoslaw; Intel Graphics Development; Goel,
Akash
Subject: Re: Why idle_freq is set to RPn and not RPe

On Wed, Dec 30, 2015 at 02:51:27PM +0530, Kamble, Sagar A wrote:

Hi Chris,

With below commit, idle frequency is made RPn (HW Min).
Why are we not keeping it at RPe (Efficient Frequency)?
My understanding was to set Rpe on idle so that when GPU is out of
RC6 it can start operating at efficient frequency.

The driver is *idle*. When there is work to be submitted to the GPU, then
we go back to RPe (though we wait for it to wake up first). RPe is just an
inflexion point on the power curve.
-Chris

--
Chris Wilson, Intel Open Source Technology Centre

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