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 1A1E0CDB465 for ; Thu, 19 Oct 2023 06:42:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232760AbjJSGmL (ORCPT ); Thu, 19 Oct 2023 02:42:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44472 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232383AbjJSGmJ (ORCPT ); Thu, 19 Oct 2023 02:42:09 -0400 Received: from out30-124.freemail.mail.aliyun.com (out30-124.freemail.mail.aliyun.com [115.124.30.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9518D116 for ; Wed, 18 Oct 2023 23:42:02 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R171e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046060;MF=tianruidong@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VuT-mP5_1697697717; Received: from 30.221.133.189(mailfrom:tianruidong@linux.alibaba.com fp:SMTPD_---0VuT-mP5_1697697717) by smtp.aliyun-inc.com; Thu, 19 Oct 2023 14:41:58 +0800 Message-ID: <29149b0c-c7eb-d900-eda8-5f3e1cb9eccc@linux.alibaba.com> Date: Thu, 19 Oct 2023 14:41:55 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH] coresight: etm4x: Enable ETE device accessed via MMIO Content-Language: en-US To: Suzuki K Poulose , linux-kernel@vger.kernel.org Cc: james.clark@arm.com, coresight@lists.linaro.org, mike.leach@linaro.org, alexander.shishkin@linux.intel.com, linux-arm-kernel@lists.infradead.org References: <20231018070506.65320-1-tianruidong@linux.alibaba.com> <206d5b79-dcd8-05b7-86c8-d6fb5790439e@linux.alibaba.com> From: Ruidong Tian In-Reply-To: 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 Suzuki You are right, I review armv9 Spec again, and find that ETE only support system instructions access.  This patch is meaningless and need to drop it. Ruidong 在 2023/10/18 17:36, Suzuki K Poulose 写道: > Hi > > On 18/10/2023 10:30, Ruidong Tian wrote: >> Hi Suzuki, >> >> Now ETM4X driver use MMIO or system instruction depends on this check >> in function etm4_init_csdev_access: >> >>          if (drvdata->base) >>                  return etm4_init_iomem_access(drvdata, csa); >> >> This check always true if firmware provides a address range in ACPI >> table of ETE, and as a result, the ETE device in this case cannot be >> successfully probed. >> >> I think OS should be compatible with this situation, no matter firmware >> how to organize ETE information in ACPI table. How do you feel about >> it? > > My question is not about "What the patch does". But, why can't we use > system instructions on your system, when ETE was designed to be used > with that in the first place and get rid of the MMIO. > > Suzuki > >> >> Thank you >> >> Ruidong Tian >> 在 2023/10/18 16:28, Suzuki K Poulose 写道: >>> On 18/10/2023 08:05, Ruidong Tian wrote: >>>> The ETM4X driver now assume that all ETE as CPU system instructions >>>> accessed device, in fact the ETE device on some machines also accessed >>>> via MMIO. >>>> >>>> Signed-off-by: Ruidong Tian >>> >>> Why are we going backwards to MMIO from system instructions ? Is it >>> because of an "unfriendly" hypervisor preventing access ? >>> >>> As such, without a sufficiently acceptable explanation, I am reluctant >>> to make this change >>> >>> Suzuki >>> >>>> --- >>>>   drivers/hwtracing/coresight/coresight-etm4x-core.c | 5 +++-- >>>>   1 file changed, 3 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c >>>> b/drivers/hwtracing/coresight/coresight-etm4x-core.c >>>> index 285539104bcc..ad298c9cc87e 100644 >>>> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c >>>> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c >>>> @@ -1103,8 +1103,9 @@ static bool etm4_init_iomem_access(struct >>>> etmv4_drvdata *drvdata, >>>>        * with MMIO. But we cannot touch the OSLK until we are >>>>        * sure this is an ETM. So rely only on the TRCDEVARCH. >>>>        */ >>>> -    if ((devarch & ETM_DEVARCH_ID_MASK) != ETM_DEVARCH_ETMv4x_ARCH) { >>>> -        pr_warn_once("TRCDEVARCH doesn't match ETMv4 >>>> architecture\n"); >>>> +    if ((devarch & ETM_DEVARCH_ID_MASK) != ETM_DEVARCH_ETMv4x_ARCH && >>>> +        (devarch & ETM_DEVARCH_ID_MASK) != ETM_DEVARCH_ETE_ARCH) { >>>> +        pr_warn_once("TRCDEVARCH doesn't match ETMv4/ETE >>>> architecture\n"); >>>>           return false; >>>>       }