From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755111AbcIAPNQ (ORCPT ); Thu, 1 Sep 2016 11:13:16 -0400 Received: from mail-wm0-f41.google.com ([74.125.82.41]:36896 "EHLO mail-wm0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753807AbcIAPNP (ORCPT ); Thu, 1 Sep 2016 11:13:15 -0400 MIME-Version: 1.0 In-Reply-To: <69b45eb1-6b4b-329d-c833-5846f222119e@arm.com> References: <1472573965-3881-1-git-send-email-mathieu.poirier@linaro.org> <1472573965-3881-6-git-send-email-mathieu.poirier@linaro.org> <94a6e940-cce8-a179-fe0c-c69a543e302c@arm.com> <69b45eb1-6b4b-329d-c833-5846f222119e@arm.com> From: Mathieu Poirier Date: Thu, 1 Sep 2016 09:13:12 -0600 Message-ID: Subject: Re: [PATCH V7 5/5] perf tools: adding sink configuration for cs_etm PMU To: Suzuki K Poulose Cc: Arnaldo Carvalho de Melo , Arnaldo Carvalho de Melo , Peter Zijlstra , jolsa@kernel.org, Ingo Molnar , Alexander Shishkin , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1 September 2016 at 03:04, Suzuki K Poulose wrote: > On 31/08/16 15:14, Mathieu Poirier wrote: >> >> On 31 August 2016 at 03:37, Suzuki K Poulose >> wrote: >>> >>> On 30/08/16 17:19, Mathieu Poirier wrote: >>>> >>>> >>>> Using the PMU::set_drv_config() callback to enable the CoreSight >>>> sink that will be used for the trace session. >>> >>> >>> >>>> +int cs_etm_set_drv_config(struct perf_evsel_config_term *term) >>>> +{ >>>> + int ret; >>>> + char enable_sink[ENABLE_SINK_MAX]; >>>> + >>>> + snprintf(enable_sink, ENABLE_SINK_MAX, "%s/%s", >>>> + term->val.drv_cfg, "enable_sink"); >>>> + >>>> + ret = cs_device__print_file(enable_sink, "%d", 1); >>>> + if (ret < 0) >>>> + return ret; >>>> + >>>> + return 0; >>>> +} >>> >>> >>> >>> >>> Don't we have to disable the sink at the end of the session ? How is that >>> taken care of ? Did I miss that ? >>> >> >> Correct - the sink has to be disabled once it is no longer needed. It >> is a little tricky to do and I haven't decided on the best way to >> proceed. Fortunately that aspect doesn't affect this patchset. > > > Well, this patchset when used, could leave a sink enabled. At this time it does yes, but that is a problem inherent to the CoreSight framework rather than perf's ability to push driver specific configuration to the PMU drivers. That is the reason why I decided to address this issue in a later patch. There is also the fact that I haven't heard back from Arnaldo on this approach - if I get asked to proceed differently then the method for disabling sinks will have to change. > If we a choose > a different sink (say an ETF) from the perf, which occurs before the > previous sink (say an ETR) in the coresight path, the perf wouldn't get any > trace data, without any clue. > > May be we could register an atexit() handler for clearing the sink ? So that > it is guaranteed to clear it irrespective of the path taken by perf to exit > ? Yes, that would be the most intuitive solution but it won't work for CoreSight. The PMU driver allows multiple traces session to exist concurrently and that, with different sinks for each session (if the HW topology supports it). As such the sink for a session needs to be disabled at driver level as soon as it got recognised in the configuration of a path. That way the next session, which may start before the previous one ended, doesn't trip on the sink that was selected earlier. I thought about a solution and I think it can work but before moving ahead with it, I need to have an idea of how this patchset will go. Thanks for the comments, Mathieu > > Cheers > Suzuki >