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Wed, 30 Sep 2026 23:37:47 -0700 (PDT) Received: from localhost (2620:10d:c0a8:1b::30) by mail.thefacebook.com (2620:10d:c0a9:6f::237c) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.2.2562.49; Thu, 1 Oct 2026 06:37:46 +0000 From: Amir Ayupov To: James Clark , Leo Yan , Suzuki K Poulose , Mike Leach , Alexander Shishkin CC: Jonathan Corbet , Shuah Khan , Randy Dunlap , , , , Subject: [PATCH 2/2] coresight: Add pmu_pulse/extout_pulse Date: Wed, 30 Sep 2026 23:37:44 -0700 Message-ID: <20261001063744.2143819-2-aaupov@fb.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20261001063744.2143819-1-aaupov@fb.com> References: <20261001063744.2143819-1-aaupov@fb.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Authority-Analysis: v=2.4 cv=D47SufRj c=1 sm=1 tr=0 ts=6abdffbc cx=c_pps a=MfjaFnPeirRr97d5FC5oHw==:117 a=MfjaFnPeirRr97d5FC5oHw==:17 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=7x6HtfJdh03M6CCDgxCd:22 a=03ozwUkBphtHgyqjj1sw:22 a=FOH2dFAWAAAA:8 a=7zQ8FAL6pVqGlCbRy-AA:9 X-Proofpoint-ORIG-GUID: WXjDZuJqAgYmGpzdcYpF4xPUZiitT28S X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDAxMDAyNSBTYWx0ZWRfX/cPYGBgFP45z ryPTrSCbakrOVSZ8fGoDQgtJx1vmNPYwXpimL+a1wXH7c3J7celGYV99yqqAvmjGAg+LC+NeGEr afTLZdG0lGgdVfmtcpd0Fd5PW020w+WLLPSiWs9y9SfiY6OuhDdi88LBxT0BYGCGQ05ghDnTxfa frvRNGoM/c2oIMdJzZoq5R96xb+HXzHPSQZBv0SQNumFUQd9gWDVTm0Y+N0yRj3UTcbJR//wujO IhTm8L3rKVyXO3kOfpDTVfJroatc2dNAIbfwMebdX9BSiwm6r7WJgpoKjcf+0McxVJlMZzrxiQR tSojcm4UjnEvUAGw+oNV9cKXf+1V6udP4wILk+jR/ByVQfhzm5KU8dJB+wrmjt7HRsrjGyiRtO3 1x4+n4nQ+l1xD8f/8Hy5KlN6yjoo4I7gFkW+TzzSyQZoSgb/t5/z1D0VZpbCKuioLMPJfSdwRwv 6obWczRhYOsfWQF4o2A== X-Proofpoint-GUID: WXjDZuJqAgYmGpzdcYpF4xPUZiitT28S X-Proofpoint-Spam-Info: AW1haW4tMjYxMDAxMDAyNSBTYWx0ZWRfX+y11nNHnt/Gx w3WOZt0QtGUylfgYaQyWZiuU+w2TuxwNgWTYLVNabfg00W10uQGx4zaHDXTCVijgLb1ie+PXuHb dbplI6fUFTba8mnfZ614ufMXrwCt0+o= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-10-01_02,2026-09-21_02,2025-10-01_01 Add ETMv4 configuration 'pmu_pulse' with 'extout_pulse' feature which requires CS_CFG_MATCH_CAP_PMU_EXTOUT1: event 1 selects the always-true resource and drives TRCEXTOUT1 PMU event which pulses on every cycle while the trace unit is enabled. The intended use is for CSSPGO profiling: a fixed-length ETM strobing window that ends at a PMU event. The window is decoded into branch stack, PMU event is carrying callchains. pmu_pulse allows specifying the window in ETM cycles. Assisted-by: Devmate:Opus-5.5 Signed-off-by: Amir Ayupov --- .../trace/coresight/coresight-config.rst | 5 ++ .../trace/coresight/coresight-perf.rst | 19 +++++++ drivers/hwtracing/coresight/Makefile | 1 + .../coresight/coresight-cfg-pmu-pulse.c | 55 +++++++++++++++++++ .../coresight/coresight-cfg-preload.c | 2 + .../coresight/coresight-cfg-preload.h | 2 + 6 files changed, 84 insertions(+) create mode 100644 drivers/hwtracing/coresight/coresight-cfg-pmu-pulse.c diff --git a/Documentation/trace/coresight/coresight-config.rst b/Documentation/trace/coresight/coresight-config.rst index 6d5ffa6f73471..3eed728bf0de1 100644 --- a/Documentation/trace/coresight/coresight-config.rst +++ b/Documentation/trace/coresight/coresight-config.rst @@ -129,6 +129,11 @@ The following steps take place in the operation of a configuration. 5) At the end of the perf session, the configuration will be disabled. +The built-in 'pmu_pulse' configuration pulses ETM external output 1 for a PMU +event to count. It only pulses while the ETM is enabled, so combined with AUX +pause and resume the PMU event can time each trace window (see +coresight-perf.rst). + Viewing Configurations and Features =================================== diff --git a/Documentation/trace/coresight/coresight-perf.rst b/Documentation/trace/coresight/coresight-perf.rst index 0a77741a431ef..b5c0c0acbe1de 100644 --- a/Documentation/trace/coresight/coresight-perf.rst +++ b/Documentation/trace/coresight/coresight-perf.rst @@ -109,6 +109,25 @@ Example for triggering AUX pause and resume with PMU event:: -e cycles/aux-action=pause,period=10000000/ \ -e cycles/aux-action=resume,period=1050000/ -- sleep 1 +ETM-timed pause events +~~~~~~~~~~~~~~~~~~~~~~ + +The built-in ``pmu_pulse`` configuration pulses ETM external output 1 on every +cycle of allowed trace, and a PMU event counting that output pauses trace after +``N`` pulses, here 1000 cycles:: + + perf record -T \ + -e cs_etm/pmu_pulse,aux-action=start-paused,timestamp/u \ + -e armv8_pmuv3_0/cpu_cycles,aux-action=resume,period=1050031/u \ + -e armv8_pmuv3_0/trcextout1,aux-action=pause,period=1000,call-graph=fp/u \ + -- ./workload + +Each window is about ``N`` traced cycles plus the pause interrupt latency, so +windows are never empty and a callchain on the pause event is taken where +trace ends. The configuration only loads where the PMU counts ETM external +output 1 (Cortex-A520, Cortex-X925, Neoverse N2, N3, V2 and V3); elsewhere a +session selecting it fails to start. + Perf test - Verify kernel and userspace perf CoreSight work ----------------------------------------------------------- diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile index ab16d06783a57..568e797ac5a17 100644 --- a/drivers/hwtracing/coresight/Makefile +++ b/drivers/hwtracing/coresight/Makefile @@ -28,6 +28,7 @@ obj-$(CONFIG_CORESIGHT) += coresight.o coresight-y := coresight-core.o coresight-etm-perf.o coresight-platform.o \ coresight-sysfs.o coresight-syscfg.o coresight-config.o \ coresight-cfg-preload.o coresight-cfg-afdo.o coresight-cfg-pstop.o \ + coresight-cfg-pmu-pulse.o \ coresight-syscfg-configfs.o coresight-trace-id.o obj-$(CONFIG_CORESIGHT_LINK_AND_SINK_TMC) += coresight-tmc.o coresight-tmc-y := coresight-tmc-core.o coresight-tmc-etf.o \ diff --git a/drivers/hwtracing/coresight/coresight-cfg-pmu-pulse.c b/drivers/hwtracing/coresight/coresight-cfg-pmu-pulse.c new file mode 100644 index 0000000000000..643c9a12018d8 --- /dev/null +++ b/drivers/hwtracing/coresight/coresight-cfg-pmu-pulse.c @@ -0,0 +1,55 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Pulse ETM external output 1 on every traced cycle for a PMU event to count. + * Based on coresight-cfg-afdo.c + */ + +#include "coresight-config.h" + +/* ETMv4 includes and features */ +#if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM4X) +#include "coresight-etm4x-cfg.h" + +/* + * extout_pulse feature: event 1 selects the always-true resource, so ETM + * external output 1 pulses on every cycle while the trace unit is enabled. A + * PMU event counting that output (TRCEXTOUT1), for example with + * aux-action=pause, then fires after as many traced cycles as its sample + * period. Event 0 is avoided because it is the trace unit trigger, and the + * TRBE driver treats a detected trigger as fatal. + */ +static struct cscfg_regval_desc extout_pulse_regs[] = { + /* event 1: resource selector 1 (always true), drives external output 1 */ + { + .type = CS_CFG_REG_TYPE_STD | CS_CFG_REG_TYPE_VAL_MASK, + .offset = TRCEVENTCTL0R, + .val32 = 0x0100, + .mask32 = 0xff00, + }, + /* end of regs */ +}; + +struct cscfg_feature_desc extout_pulse_etm4x = { + .name = "extout_pulse", + .description = "Pulse external output 1 on every traced cycle.\n", + .match_flags = CS_CFG_MATCH_CAP_PMU_EXTOUT1, + .nr_regs = ARRAY_SIZE(extout_pulse_regs), + .regs_desc = extout_pulse_regs, +}; + +/* create a pmu_pulse configuration */ + +static const char * const pmu_pulse_ref_names[] = { + "extout_pulse", +}; + +struct cscfg_config_desc pmu_pulse_etm4x = { + .name = "pmu_pulse", + .description = "Pulse ETM external output 1 on every traced cycle for the PMU\n" + "to count as TRCEXTOUT1\n", + .nr_feat_refs = ARRAY_SIZE(pmu_pulse_ref_names), + .feat_ref_names = pmu_pulse_ref_names, +}; + +/* end of ETM4x configurations */ +#endif /* IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM4X) */ diff --git a/drivers/hwtracing/coresight/coresight-cfg-preload.c b/drivers/hwtracing/coresight/coresight-cfg-preload.c index 4980e68483c5b..a9a60a1c40845 100644 --- a/drivers/hwtracing/coresight/coresight-cfg-preload.c +++ b/drivers/hwtracing/coresight/coresight-cfg-preload.c @@ -14,6 +14,7 @@ static struct cscfg_feature_desc *preload_feats[] = { #if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM4X) &strobe_etm4x, &gen_etrig_etm4x, + &extout_pulse_etm4x, #endif NULL }; @@ -22,6 +23,7 @@ static struct cscfg_config_desc *preload_cfgs[] = { #if IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM4X) &afdo_etm4x, &pstop_etm4x, + &pmu_pulse_etm4x, #endif NULL }; diff --git a/drivers/hwtracing/coresight/coresight-cfg-preload.h b/drivers/hwtracing/coresight/coresight-cfg-preload.h index 291ba530a6a52..0058627f65ae5 100644 --- a/drivers/hwtracing/coresight/coresight-cfg-preload.h +++ b/drivers/hwtracing/coresight/coresight-cfg-preload.h @@ -12,4 +12,6 @@ extern struct cscfg_feature_desc strobe_etm4x; extern struct cscfg_config_desc afdo_etm4x; extern struct cscfg_feature_desc gen_etrig_etm4x; extern struct cscfg_config_desc pstop_etm4x; +extern struct cscfg_feature_desc extout_pulse_etm4x; +extern struct cscfg_config_desc pmu_pulse_etm4x; #endif -- 2.52.0