From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hilman Subject: Re: [PATCH 7/8] OMAP: omap_device: warn about expected latencies only if non-zero Date: Thu, 19 Nov 2009 11:08:39 -0800 Message-ID: <87r5ru8h8o.fsf@deeprootsystems.com> References: <1258506313-17115-1-git-send-email-khilman@deeprootsystems.com> <1258506313-17115-2-git-send-email-khilman@deeprootsystems.com> <1258506313-17115-3-git-send-email-khilman@deeprootsystems.com> <1258506313-17115-4-git-send-email-khilman@deeprootsystems.com> <1258506313-17115-5-git-send-email-khilman@deeprootsystems.com> <1258506313-17115-6-git-send-email-khilman@deeprootsystems.com> <1258506313-17115-7-git-send-email-khilman@deeprootsystems.com> <1258506313-17115-8-git-send-email-khilman@deeprootsystems.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-pw0-f42.google.com ([209.85.160.42]:33201 "EHLO mail-pw0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751634AbZKSTIe (ORCPT ); Thu, 19 Nov 2009 14:08:34 -0500 Received: by pwi3 with SMTP id 3so1587337pwi.21 for ; Thu, 19 Nov 2009 11:08:41 -0800 (PST) In-Reply-To: (Paul Walmsley's message of "Wed\, 18 Nov 2009 04\:19\:20 -0700 \(MST\)") Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Paul Walmsley Cc: linux-omap@vger.kernel.org Paul Walmsley writes: > Hi, > > On Tue, 17 Nov 2009, Kevin Hilman wrote: > >> When checking measured [de]activate latencies against expected >> latencies, only print warning if driver has provided a non-zero >> latency. >> >> This allows drivers to set their [de]activate latencies to zero when >> they are not known, or are don't care, and the omap_device core will >> not complain about unexpected latencies. > > I'm concerned that this will effectively mean that no driver maintainers > will bother to measure these latencies. > > These are necessary for a reasonable implementation of > omap_pm_set_max_dev_wakeup_lat(). They should not be difficult to > measure: boot at the lowest-performance OPPs with the latencies > uninitialized; then these warnings should indicate numbers that can > be plugged back into the omap_device structure. But perhaps I am > misunderstanding the point you are making? Part of the issue is being able to do a quick conversion, without needing to measure latencies (which I'm guilty of.) The other part was that I was thinking (the RFC part) was that it might be useful for performance reasons to not do do any measuring at all. Of course, this would preclude a useful max_dev_wakeup_lat() but we could warn about that. But, for now I agree. I think getting these latencies in place is more important than having an optimization for avoiding measurement for now. Kevin