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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 3A1C8C43387 for ; Fri, 18 Jan 2019 12:04:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 157202086D for ; Fri, 18 Jan 2019 12:04:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727429AbfARME0 (ORCPT ); Fri, 18 Jan 2019 07:04:26 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:55792 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727230AbfARMEZ (ORCPT ); Fri, 18 Jan 2019 07:04:25 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 59CED80D; Fri, 18 Jan 2019 04:04:25 -0800 (PST) Received: from [10.1.196.93] (en101.cambridge.arm.com [10.1.196.93]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5A4E43F557; Fri, 18 Jan 2019 04:04:22 -0800 (PST) Subject: Re: [PATCHv2 2/4] arm64: dts: qcom: msm8996: Add Coresight support To: saiprakash.ranjan@codeaurora.org, robh+dt@kernel.org, mathieu.poirier@linaro.org, leo.yan@linaro.org, alexander.shishkin@linux.intel.com, andy.gross@linaro.org, david.brown@linaro.org, vivek.gautam@codeaurora.org, dianders@chromium.org, sboyd@kernel.org, bjorn.andersson@linaro.org, devicetree@vger.kernel.org, mark.rutland@arm.com Cc: rnayak@codeaurora.org, sibis@codeaurora.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org References: <552e408950525b1bac39d05b8b4f2ae1975397e0.1547798966.git.saiprakash.ranjan@codeaurora.org> <1311e78a-21f6-6470-7861-39b3499974ce@arm.com> <6543ad5c-bbcf-b3ec-332c-115e8e3d0825@codeaurora.org> From: Suzuki K Poulose Message-ID: <1b7d4c2f-98f7-4b80-4e32-6e0fe5c906ce@arm.com> Date: Fri, 18 Jan 2019 12:04:20 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <6543ad5c-bbcf-b3ec-332c-115e8e3d0825@codeaurora.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 18/01/2019 11:48, Sai Prakash Ranjan wrote: > Hi Suzuki, > > On 1/18/2019 4:27 PM, Suzuki K Poulose wrote: >> >> If you want to use the scatter-gather mode, you must add >> "arm,scatter-gather" >> property to the node here. >> >> Have you tested the scatter-gather mode on the chip ? Does that work at >> all ? >> Note: You could try this by setting a buffer_size > 1M for the ETR and use >> it as a sink from the sysfs mode. >> > > Yes the chip supports scatter-gather mode[1]. But is it required in > dt node since it's an optional property? If you would like to use the scatter-gather mode, you must specify it explicitly. We have had some other boards with broken scatter-gather mode integration which causes mysterious issues when used. So we have a white-list approach for enabling the scatter-gather mode in the driver. So, if you have tested to make sure that the mode works fine with a recent kernel version (v4.19 onwards), you may want to add the property. Suzuki