From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3EE45C433DB for ; Fri, 15 Jan 2021 13:03:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1147F22473 for ; Fri, 15 Jan 2021 13:03:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731903AbhAOMca (ORCPT ); Fri, 15 Jan 2021 07:32:30 -0500 Received: from foss.arm.com ([217.140.110.172]:38832 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728163AbhAOMcK (ORCPT ); Fri, 15 Jan 2021 07:32:10 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id F112EED1; Fri, 15 Jan 2021 04:31:24 -0800 (PST) Received: from [10.57.56.97] (unknown [10.57.56.97]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6A9873F70D; Fri, 15 Jan 2021 04:31:23 -0800 (PST) Subject: Re: [PATCH V2 08/11] coresight: core: Add support for dedicated percpu sinks To: Anshuman Khandual , linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org Cc: mathieu.poirier@linaro.org, mike.leach@linaro.org, Linu Cherian , linux-kernel@vger.kernel.org References: <1610511498-4058-1-git-send-email-anshuman.khandual@arm.com> <1610511498-4058-9-git-send-email-anshuman.khandual@arm.com> <83939b79-31de-2984-7418-7e4c026dba3a@arm.com> <6dc0baeb-cc9b-562b-ac4d-03fe894be099@arm.com> From: Suzuki K Poulose Message-ID: <1ae508a9-69f5-af33-acd0-d305f6039187@arm.com> Date: Fri, 15 Jan 2021 12:31:14 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <6dc0baeb-cc9b-562b-ac4d-03fe894be099@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/15/21 2:36 AM, Anshuman Khandual wrote: > > > On 1/13/21 3:13 PM, Suzuki K Poulose wrote: >> On 1/13/21 4:18 AM, Anshuman Khandual wrote: >>> Add support for dedicated sinks that are bound to individual CPUs. (e.g, >>> TRBE). To allow quicker access to the sink for a given CPU bound source, >>> keep a percpu array of the sink devices. Also, add support for building >>> a path to the CPU local sink from the ETM. >>> >>> This adds a new percpu sink type CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM. >>> This new sink type is exclusively available and can only work with percpu >>> source type device CORESIGHT_DEV_SUBTYPE_SOURCE_PERCPU_PROC. >>> >>> This defines a percpu structure that accommodates a single coresight_device >>> which can be used to store an initialized instance from a sink driver. As >>> these sinks are exclusively linked and dependent on corresponding percpu >>> sources devices, they should also be the default sink device during a perf >>> session. >>> >>> Outwards device connections are scanned while establishing paths between a >>> source and a sink device. But such connections are not present for certain >>> percpu source and sink devices which are exclusively linked and dependent. >>> Build the path directly and skip connection scanning for such devices. >>> >>> Cc: Mathieu Poirier >>> Cc: Mike Leach >>> Cc: Suzuki K Poulose >>> Signed-off-by: Anshuman Khandual >>> --- >>>   drivers/hwtracing/coresight/coresight-core.c | 14 ++++++++++++++ >>>   include/linux/coresight.h                    | 12 ++++++++++++ >>>   2 files changed, 26 insertions(+) >>> >>> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c >>> index 0062c89..b300606 100644 >>> --- a/drivers/hwtracing/coresight/coresight-core.c >>> +++ b/drivers/hwtracing/coresight/coresight-core.c >>> @@ -23,6 +23,7 @@ >>>   #include "coresight-priv.h" >>>     static DEFINE_MUTEX(coresight_mutex); >>> +DEFINE_PER_CPU(struct coresight_device *, csdev_sink); >>>     /** >>>    * struct coresight_node - elements of a path, from source to sink >>> @@ -784,6 +785,13 @@ static int _coresight_build_path(struct coresight_device *csdev, >>>       if (csdev == sink) >>>           goto out; >>>   +    if (coresight_is_percpu_source(csdev) && coresight_is_percpu_sink(sink) && >>> +        sink == per_cpu(csdev_sink, source_ops(csdev)->cpu_id(csdev))) { >>> +        _coresight_build_path(sink, sink, path); >>> +        found = true; >>> +        goto out; >>> +    } >>> + >>>       /* Not a sink - recursively explore each port found on this element */ >>>       for (i = 0; i < csdev->pdata->nr_outport; i++) { >>>           struct coresight_device *child_dev; >>> @@ -998,6 +1006,12 @@ coresight_find_default_sink(struct coresight_device *csdev) >>>   { >>>       int depth = 0; >>>   +    if (coresight_is_percpu_source(csdev)) { >> >> On a system without per_cpu sink, this would reset the default sink for the source device >> every single time and fallback to searching every single time. > > Right. > >> So I think it would be better if did check if the def_sink was not set. >> We could fold this into the case below may be. i.e, >> >> >>     if (!csdev->def_sink) { >>         if (coresight_is_percpu_source(csdev)) >>             csdev->def_sink = per_cpu(csdev_sink, source_ops(csdev)->cpu_id(csdev)); >>         if (!csdev->def_sink)            csdev->def_sink = coresight_find_sink(csdev, &depth); >>     } >> >> Otherwise looks good to me. > > struct coresight_device * > coresight_find_default_sink(struct coresight_device *csdev) > { > int depth = 0; > > /* look for a default sink if we have not found for this device */ > if (!csdev->def_sink) { > if (coresight_is_percpu_source(csdev)) > csdev->def_sink = per_cpu(csdev_sink, source_ops(csdev)->cpu_id(csdev)); > if (!csdev->def_sink) > csdev->def_sink = coresight_find_sink(csdev, &depth); > } > return csdev->def_sink; > } > > Would this be better instead ? coresight_find_sink() is invoked both when the > source is not percpu (traditional coresight sources) and also as a fallback in > case a percpu sink is not found for the percpu source device. Yes, this is exactly what I proposed above. Cheers Suzuki