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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A0111C83F11 for ; Sun, 27 Aug 2023 21:36:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230258AbjH0Vfa (ORCPT ); Sun, 27 Aug 2023 17:35:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42750 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230245AbjH0VfX (ORCPT ); Sun, 27 Aug 2023 17:35:23 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 687B0107 for ; Sun, 27 Aug 2023 14:35:19 -0700 (PDT) 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 61D6E1FB; Sun, 27 Aug 2023 14:35:59 -0700 (PDT) Received: from [10.57.3.66] (unknown [10.57.3.66]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D607B3F738; Sun, 27 Aug 2023 14:35:17 -0700 (PDT) Message-ID: <1b2a035c-489e-ace9-f851-c1ec157ff9fa@arm.com> Date: Sun, 27 Aug 2023 22:35:16 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.14.0 Subject: Re: [PATCH V2] coresight: tmc: Make etr buffer mode user configurable from sysfs To: scclevenger@os.amperecomputing.com, Anshuman Khandual , linux-arm-kernel@lists.infradead.org Cc: Mike Leach , James Clark , Leo Yan , Alexander Shishkin , coresight@lists.linaro.org, linux-kernel@vger.kernel.org References: <20230818082112.554638-1-anshuman.khandual@arm.com> <391951c3-7da9-3965-acf8-f3b31f822879@os.amperecomputing.com> From: Suzuki K Poulose In-Reply-To: <391951c3-7da9-3965-acf8-f3b31f822879@os.amperecomputing.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Steve On 26/08/2023 01:14, Steve Clevenger wrote: > > Unfortunately, I tested with the original patch not [PATCH V2]. I've > remedied this. My results below: > > [root@sut01sys-b212 linux]# cat > /sys/devices/system/cpu/cpu123/ARMHC501\:23/tmc_etr35/buf_modes_available > auto flat catu > [root@sut01sys-b212 linux]# cat > /sys/devices/system/cpu/cpu123/ARMHC501\:23/tmc_etr35/buf_mode_preferred > auto > [root@sut01sys-b212 linux]# echo "catu" > > /sys/devices/system/cpu/cpu123/ARMHC501\:23/tmc_etr35/buf_mode_preferred > [root@sut01sys-b212 linux]# cat > /sys/devices/system/cpu/cpu123/ARMHC501\:23/tmc_etr35/buf_mode_preferred > catu > > As with the V1 patch, auto defaults to catu. > > I expected to see tmc-sg (former default) as an available mode, but do > not. As I recall, the buffer mode defaulted to ETR scatter-gather prior > to this patch. Must this capability now be explicitly advertised? I've > seen this done as "arm,scatter-gather" in device trees, but not used by > Ampere. Perhaps someone can enlighten me. Yes, you must add that property to the TMC-ETR node (for both DT and ACPI). In the past, almost all of the TMC-ETRs (except Juno board) locked up the system while using the SG mode (due to the interconnect issues, something to do with the transaction). Thus, we decided to add a property explicitly enabling this for a given platform. When you mentioned, it was using TMC-ETR SG mode, how did you verify this ? Please be aware that the table allocation code etc are shared by both TMC-SG and CATU. Kind regards Suzuki > > Steve C. > > On 8/23/2023 4:10 PM, Steve Clevenger wrote: >> >> Here's some quick feedback. My system shows two modes available; auto catu >> >> etr_buf_mode_current is writable. I expected to see tmc-sg (former >> default) listed in etr_buf_modes_available but it doesn't show up. >> >> Note that both the auto and catu etr_buf_mode_current settings default >> to catu. My understanding is auto should revert to the default behavior. >> On my system the default was tmc-sg. >> >> More later. >> >> [root@sut01sys-b212 kernel]# cat >> /sys/devices/system/cpu/cpu20/ARMHC501\:60/tmc_etr96/etr_buf_modes_available >> >> auto catu >> [root@sut01sys-b212 kernel]# cat >> /sys/devices/system/cpu/cpu20/ARMHC501\:60/tmc_etr96/etr_buf_mode_current >> catu >> [root@sut01sys-b212 kernel]# echo "catu" > >> /sys/devices/system/cpu/cpu20/ARMHC501\:60/tmc_etr96/etr_buf_mode_current >> [root@sut01sys-b212 kernel]# cat >> /sys/devices/system/cpu/cpu20/ARMHC501\:60/tmc_etr96/etr_buf_mode_current >> catu >> >> Steve C. >> >> >> On 8/21/2023 12:40 PM, Steve Clevenger wrote: >>> >>> Hi Suzuki, >>> >>> I may be able to test it this week. You've already pointed me at the >>> patch thread(s). The main holdup is I need to merge the 6.6 pending >>> platform work in order to use the Ampere ACPI. I couldn't get these >>> patches to apply directly to 6.4 last I tried. >>> >>> Steve C. >>> >>> On 8/18/2023 2:39 AM, Suzuki K Poulose wrote: >>>> Cc: Steve >>>> >>>> Steve, >>>> >>>> Are you able to test this with CATU ? >>>> >>>> >>>> On 18/08/2023 09:21, Anshuman Khandual wrote: >>>>> Currently TMC-ETR automatically selects the buffer mode from all >>>>> available >>>>> methods in the following sequentially fallback manner - also in that >>>>> order. >>>>> >>>>> 1. FLAT mode with or without IOMMU >>>>> 2. TMC-ETR-SG (scatter gather) mode when available >>>>> 3. CATU mode when available >>>>> >>>>> But this order might not be ideal for all situations. For example if >>>>> there >>>>> is a CATU connected to ETR, it may be better to use TMC-ETR scatter >>>>> gather >>>>> method, rather than CATU. But hard coding such order changes will prevent >>>>> us from testing or using a particular mode. This change provides >>>>> following >>>>> new sysfs tunables for the user to control TMC-ETR buffer mode >>>>> explicitly, >>>>> if required. This adds following new sysfs files for buffer mode >>>>> selection >>>>> purpose explicitly in the user space. >>>>> >>>>> /sys/bus/coresight/devices/tmc_etr/buf_modes_available >>>>> /sys/bus/coresight/devices/tmc_etr/buf_mode_preferred >>>>> >>>>> $ cat buf_modes_available >>>>> auto flat tmc-sg catu    ------------------> Supported TMC-ETR buffer >>>>> modes >>>>> >>>>> $ echo catu > buf_mode_preferred   -------> Explicit buffer mode request >>>>> >>>>> But explicit user request has to be within supported ETR buffer modes >>>>> only. >>>>> These sysfs interface files are exclussive to ETR, and hence these are >>>>> not >>>>> available for other TMC devices such as ETB or ETF etc. >>>>> >>>>> A new auto' mode (i.e ETR_MODE_AUTO) has been added to help fallback >>>>> to the >>>>> existing default behaviour, when user provided preferred buffer mode >>>>> fails. >>>>> ETR_MODE_FLAT and ETR_MODE_AUTO are always available as preferred modes. >>>>> >>>>> Cc: Suzuki K Poulose >>>>> Cc: Mike Leach >>>>> Cc: James Clark >>>>> Cc: Leo Yan >>>>> Cc: Alexander Shishkin >>>>> Cc: coresight@lists.linaro.org >>>>> Cc: linux-arm-kernel@lists.infradead.org >>>>> Cc: linux-kernel@vger.kernel.org >>>>> Signed-off-by: Anshuman Khandual >>>>> --- >>>>> This applies on v6.5-rc6 >>>>> >>>>> Changes in V2: >>>>> >>>>> - Renamed sysfs file etr_buf_modes_available as buf_modes_available >>>>> - Renamed sysfs file buf_mode_current as buf_mode_preferred >>>>> - Renamed etr_supports_flat_mode() as etr_can_use_flat_mode() >>>>> - Renamed coresight_tmc_groups[] as coresight_etf_groups[] >>>>> - Reused coresight_tmc_group[] for trigger_cntr and buffer_size >>>>> - Fallback trying ETR_MODE_AUTO when user preferred mode fails >>>>> - Moved ETR sysfs details into coresight-tmc-etr.c >>>>> - Dropped etr_can_use_flat_mode() check while offering ETR_MODE_FLAT >>>>> in sysfs >>>>> - Moved struct etr_buf_hw inside coresight-tmc-etr.c >>>>> - Moved get_etr_buf_hw() and etr_can_use_flat_mode() inside >>>>> coresight-tmc-etr.c >>>>> - Updated month in >>>>> Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc >>>>> >>>>> Changes in V1: >>>>> >>>>> https://lore.kernel.org/all/20230728084837.276551-1-anshuman.khandual@arm.com/ >>>>> >>>>>   .../testing/sysfs-bus-coresight-devices-tmc   |  16 +++ >>>>>   .../hwtracing/coresight/coresight-tmc-core.c  |  15 ++- >>>>>   .../hwtracing/coresight/coresight-tmc-etr.c   | 111 ++++++++++++++++-- >>>>>   drivers/hwtracing/coresight/coresight-tmc.h   |   3 + >>>>>   4 files changed, 131 insertions(+), 14 deletions(-) >>>> >>>> >>>> Looks good to me. >>>> >>>> Suzuki >>>> >>>>