From patchwork Thu Jan 13 09:10:55 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Clark X-Patchwork-Id: 12712498 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B43A5C433F5 for ; Thu, 13 Jan 2022 09:13:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=GHYRQyz3M+BGdJ8OAO7QIvedOx+y0H78+UQKCyynJLU=; b=Oahour6NE7qI25 hxGhUay/FQKNx+4eXbxj32DJs7XhvydQe9Yc0yhwYblHOjQQEFm3Cfomm8tqbhD4Jz0gm8eYZqFsD Y2Yu2ufRxc5IGMuFdMTjNsMD3CJMn8a84lO0sHwAH+uezzKuiRatf4zC8m2dOB7Vq5bYB32BDmoaK zVGDLaHHCVjP+00lICFLuOjT8skNzsCB6wdv8Av5LehWxWN3KRUWEZCwFXNTLFshvgkVUkY/udKw7 ucPNl1KjvxmK+Djaqa9N849S7lwe3BkCf2zJNeihFeuAYdw7W7UnH1Chm/2EKE6o7LaTEzcqXuQU1 M5FY93Lb0Cuchbgk3FTQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1n7w9k-005DRP-1Q; Thu, 13 Jan 2022 09:12:28 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1n7w8k-005Cvz-2O for linux-arm-kernel@lists.infradead.org; Thu, 13 Jan 2022 09:11:27 +0000 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 62C26113E; Thu, 13 Jan 2022 01:11:25 -0800 (PST) Received: from e121896.arm.com (unknown [10.57.35.134]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id DD13D3F766; Thu, 13 Jan 2022 01:11:22 -0800 (PST) From: James Clark To: suzuki.poulose@arm.com, mathieu.poirier@linaro.org, coresight@lists.linaro.org, leo.yan@linaro.com, mike.leach@linaro.org Cc: James Clark , Leo Yan , John Garry , Will Deacon , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: [PATCH v2 6/6] Documentation: coresight: Expand branch broadcast documentation Date: Thu, 13 Jan 2022 09:10:55 +0000 Message-Id: <20220113091056.1297982-7-james.clark@arm.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20220113091056.1297982-1-james.clark@arm.com> References: <20220113091056.1297982-1-james.clark@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220113_011126_211347_8830BD4F X-CRM114-Status: GOOD ( 10.37 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Now that there is a way of enabling branch broadcast via perf, mention the possible use cases and known limitations. Signed-off-by: James Clark Reviewed-by: Mike Leach --- .../trace/coresight/coresight-etm4x-reference.rst | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/Documentation/trace/coresight/coresight-etm4x-reference.rst b/Documentation/trace/coresight/coresight-etm4x-reference.rst index 0439b4006227..ec336575919c 100644 --- a/Documentation/trace/coresight/coresight-etm4x-reference.rst +++ b/Documentation/trace/coresight/coresight-etm4x-reference.rst @@ -656,7 +656,15 @@ Bit assignments shown below:- ETM_MODE_BB **description:** - Set to enable branch broadcast if supported in hardware [IDR0]. + Set to enable branch broadcast if supported in hardware [IDR0]. The primary use for this feature + is when code is patched dynamically at run time and the full program flow may not be able to be + reconstructed using only conditional branches. + + Choosing this option will result in a significant increase in the amount of trace generated - + possible danger of overflows, or fewer instructions covered. Note, that this option also + overrides any setting of :ref:`ETM_MODE_RETURNSTACK `, so where a branch + broadcast range overlaps a return stack range, return stacks will not be available for that + range. .. _coresight-cycle-accurate: