From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wolverine02.qualcomm.com ([199.106.114.251]:31433 "EHLO wolverine02.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755245Ab0H0SdC (ORCPT ); Fri, 27 Aug 2010 14:33:02 -0400 Message-ID: <4C7804DE.9020008@codeaurora.org> Date: Fri, 27 Aug 2010 11:33:02 -0700 From: Bryan Huntsman MIME-Version: 1.0 Subject: Re: [PATCH] pm_qos: Add system bus performance parameter References: <1282882403-29824-1-git-send-email-skannan@codeaurora.org> <1282882403-29824-2-git-send-email-skannan@codeaurora.org> <87hbigqg8d.fsf@deeprootsystems.com> In-Reply-To: <87hbigqg8d.fsf@deeprootsystems.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-arm-msm-owner@vger.kernel.org List-ID: To: Kevin Hilman Cc: Saravana Kannan , linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, "Rafael J. Wysocki" , James Bottomley , mark gross , Frederic Weisbecker , Jonathan Corbet , Matthew Garrett Kevin Hilman wrote: > Saravana Kannan writes: > >> Some drivers/devices might need some minimum system bus performance to >> provide acceptable service. Provide a PM QoS parameter to send these requests >> to. >> >> The new parameter is named "system bus performance" since it is generic enough >> for the unit of the request to be frequency, bandwidth or something else that >> might be appropriate. It's up to each implementation of the QoS provider to >> define what the unit of the request would be. >> >> Signed-off-by: Saravana Kannan > > With this current design, only one system-wide bus would be managed. > What if a platform has more than one independently scalable bus? > > I think the only scalable way to handle this kind of thing is to have > per-device QoS constraints that can then be combined/aggregated by parent > devices/busses. > > At LPC this year, I've proposed per-device QoS constraints[1] as a topic > for the PM mini-conf. I hope some folks from the MSM camp can be there > for these discussions. > > Kevin > > [1] http://www.linuxplumbersconf.org/2010/ocw/proposals/819 Yeah, I'm planning on rounding up some MSM folks for LPC this year. Power is a big concern for us so it would be good to join the discussion. Initially, I was very keen on the per-device QoS contraints but I've since cooled on it. For our HW, there's not a generic unit that can convey enough data for us to act on. At least not w/o lookup tables, etc., at which point the unit loses it's value and becomes a generic handle. I'm looking forward to a good group discussion on this topic. Thanks. - Bryan -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.