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[2620:137:e000::1:20]) by mx.google.com with ESMTP id k8-20020a63d108000000b00563f711096bsi3036794pgg.852.2023.08.11.02.46.40; Fri, 11 Aug 2023 02:46:53 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=arm.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233772AbjHKJbq (ORCPT + 99 others); Fri, 11 Aug 2023 05:31:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51500 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233890AbjHKJbO (ORCPT ); Fri, 11 Aug 2023 05:31:14 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B97DA2D61; Fri, 11 Aug 2023 02:31:13 -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 CA78AD75; Fri, 11 Aug 2023 02:31:55 -0700 (PDT) Received: from [10.57.91.12] (unknown [10.57.91.12]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B51813F64C; Fri, 11 Aug 2023 02:31:11 -0700 (PDT) Message-ID: <02c1dcb7-316a-37b5-8730-ce8021274646@arm.com> Date: Fri, 11 Aug 2023 10:31:10 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH V3 1/3] coresight: etm: Override TRCIDR3.CCITMIN on errata affected cpus To: Mike Leach , Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon , James Clark , Leo Yan , Jonathan Corbet , linux-doc@vger.kernel.org, coresight@lists.linaro.org, linux-kernel@vger.kernel.org References: <20230811034600.944386-1-anshuman.khandual@arm.com> <20230811034600.944386-2-anshuman.khandual@arm.com> From: Suzuki K Poulose In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-2.9 required=5.0 tests=BAYES_00,NICE_REPLY_A, RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/08/2023 10:03, Mike Leach wrote: > Hi Anshuman, > > A few minor points. > > On Fri, 11 Aug 2023 at 04:46, Anshuman Khandual > wrote: >> >> This work arounds errata 1490853 on Cortex-A76, and Neoverse-N1, errata >> 1491015 on Cortex-A77, errata 1502854 on Cortex-X1, and errata 1619801 on >> Neoverse-V1, based affected cpus, where software read for TRCIDR3.CCITMIN >> field in ETM gets an wrong value. >> >> If software uses the value returned by the TRCIDR3.CCITMIN register field, >> then it will limit the range which could be used for programming the ETM. >> In reality, the ETM could be programmed with a much smaller value than what >> is indicated by the TRCIDR3.CCITMIN field and still function correctly. >> >> If software reads the TRCIDR3.CCITMIN register field, corresponding to the >> instruction trace counting minimum threshold, observe the value 0x100 or a >> minimum cycle count threshold of 256. The correct value should be 0x4 or a >> minimum cycle count threshold of 4. >> >> This work arounds the problem via storing 4 in drvdata->ccitmin on affected >> systems where the TRCIDR3.CCITMIN has been 256, thus preserving cycle count >> threshold granularity. >> >> These errata information has been updated in arch/arm64/silicon-errata.rst, >> but without their corresponding configs because these have been implemented >> directly in the driver. >> >> Cc: Catalin Marinas >> Cc: Will Deacon >> Cc: Suzuki K Poulose >> Cc: Mike Leach >> Cc: James Clark >> Cc: Jonathan Corbet >> Cc: linux-doc@vger.kernel.org >> Cc: coresight@lists.linaro.org >> Cc: linux-arm-kernel@lists.infradead.org >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: Anshuman Khandual >> --- >> Documentation/arch/arm64/silicon-errata.rst | 10 +++++ >> .../coresight/coresight-etm4x-core.c | 37 +++++++++++++++++++ >> 2 files changed, 47 insertions(+) >> >> diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst >> index bedd3a1d7b42..b08f33eda5f1 100644 >> --- a/Documentation/arch/arm64/silicon-errata.rst >> +++ b/Documentation/arch/arm64/silicon-errata.rst >> @@ -107,6 +107,10 @@ stable kernels. >> +----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Cortex-A76 | #1463225 | ARM64_ERRATUM_1463225 | >> +----------------+-----------------+-----------------+-----------------------------+ >> +| ARM | Cortex-A76 | #1490853 | N/A | >> ++----------------+-----------------+-----------------+-----------------------------+ >> +| ARM | Cortex-A77 | #1491015 | N/A | >> ++----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Cortex-A77 | #1508412 | ARM64_ERRATUM_1508412 | >> +----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Cortex-A510 | #2051678 | ARM64_ERRATUM_2051678 | >> @@ -125,6 +129,8 @@ stable kernels. >> +----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Cortex-A715 | #2645198 | ARM64_ERRATUM_2645198 | >> +----------------+-----------------+-----------------+-----------------------------+ >> +| ARM | Cortex-X1 | #1502854 | N/A | >> ++----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Cortex-X2 | #2119858 | ARM64_ERRATUM_2119858 | >> +----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Cortex-X2 | #2224489 | ARM64_ERRATUM_2224489 | >> @@ -133,6 +139,8 @@ stable kernels. >> +----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Neoverse-N1 | #1349291 | N/A | >> +----------------+-----------------+-----------------+-----------------------------+ >> +| ARM | Neoverse-N1 | #1490853 | N/A | >> ++----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Neoverse-N1 | #1542419 | ARM64_ERRATUM_1542419 | >> +----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Neoverse-N2 | #2139208 | ARM64_ERRATUM_2139208 | >> @@ -141,6 +149,8 @@ stable kernels. >> +----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Neoverse-N2 | #2253138 | ARM64_ERRATUM_2253138 | >> +----------------+-----------------+-----------------+-----------------------------+ >> +| ARM | Neoverse-V1 | #1619801 | N/A | >> ++----------------+-----------------+-----------------+-----------------------------+ >> | ARM | MMU-500 | #841119,826419 | N/A | >> +----------------+-----------------+-----------------+-----------------------------+ >> | ARM | MMU-600 | #1076982,1209401| N/A | > > Could these doc changes not go in patch 3? I believe no, because this patch works around the erratum and it will help anybody looking for the workaround using the list above + the patch 3 is not related to the erratum. It is simply documenting the new perf option. > >> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c >> index 703b6fcbb6a5..1f3d29a639ff 100644 >> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c >> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c >> @@ -1150,6 +1150,31 @@ static void cpu_detect_trace_filtering(struct etmv4_drvdata *drvdata) >> drvdata->trfcr = trfcr; >> } >> >> +/* >> + * The following errata on applicable cpu rangess affect the CCITMIN filed > > s/rangess/ranges > >> + * in TCRIDR3 register. Software read for the field returns 0x100 limiting >> + * the cycle threshold granularity, where as the right value should have >> + * been 0x4, which is well supported in the hardware. >> + */ >> +static struct midr_range etm_wrong_ccitmin_cpus[] = { >> + /* Erratum #1490853 - Cortex-A76 */ >> + MIDR_RANGE(MIDR_CORTEX_A76, 0, 0, 4, 0), >> + /* Erratum #1490853 - Neoverse-N1 */ >> + MIDR_RANGE(MIDR_NEOVERSE_N1, 0, 0, 4, 0), >> + /* Erratum #1491015 - Cortex-A77 */ >> + MIDR_RANGE(MIDR_CORTEX_A77, 0, 0, 1, 0), >> + /* Erratum #1502854 - Cortex-X1 */ >> + MIDR_REV(MIDR_CORTEX_X1, 0, 0), >> + /* Erratum #1619801 - Neoverse-V1 */ >> + MIDR_REV(MIDR_NEOVERSE_V1, 0, 0), >> + {}, >> +}; >> + >> +static bool etm4_work_around_wrong_ccitmin(void) > > This is not the actual work around - perhaps this should be > etm4_core_reads_wrong_ccitmin()? > >> +{ >> + return is_midr_in_range_list(read_cpuid_id(), etm_wrong_ccitmin_cpus); >> +} >> + >> static void etm4_init_arch_data(void *info) >> { >> u32 etmidr0; >> @@ -1214,6 +1239,18 @@ static void etm4_init_arch_data(void *info) >> etmidr3 = etm4x_relaxed_read32(csa, TRCIDR3); >> /* CCITMIN, bits[11:0] minimum threshold value that can be programmed */ >> drvdata->ccitmin = FIELD_GET(TRCIDR3_CCITMIN_MASK, etmidr3); >> + if (etm4_work_around_wrong_ccitmin()) { >> + /* >> + * Erratum affected cpus will read 256 as the minimum >> + * instruction trace cycle counting threshold where as >> + * the correct value should be 4 instead. Override the >> + * recorded value for 'drvdata->ccitmin' to workaround >> + * this problem. >> + */ >> + if (drvdata->ccitmin == 256) > > Not sure this check matters - fixed cores will be 4, non fixed cores > as identified by the list need to be 4, we don't care what the read > value is if the core is on the list. To be on the safer side, we may allow a core to have ccitmin more than 0x4 if we only fixup what is documented per erratum. So this looks fine to me. Suzuki > >> + drvdata->ccitmin = 4; >> + } >> + >> /* EXLEVEL_S, bits[19:16] Secure state instruction tracing */ >> drvdata->s_ex_level = FIELD_GET(TRCIDR3_EXLEVEL_S_MASK, etmidr3); >> drvdata->config.s_ex_level = drvdata->s_ex_level; >> -- >> 2.25.1 >> > > Regards > > Mike