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Mon, 29 Apr 2019 12:03:38 +0200 Received: from zeta.dmz-eu.st.com (zeta.dmz-eu.st.com [164.129.230.9]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id 88AE53D; Mon, 29 Apr 2019 10:03:37 +0000 (GMT) Received: from Webmail-eu.st.com (sfhdag5node3.st.com [10.75.127.15]) by zeta.dmz-eu.st.com (STMicroelectronics) with ESMTP id 63D281516; Mon, 29 Apr 2019 10:03:37 +0000 (GMT) Received: from SFHDAG5NODE1.st.com (10.75.127.13) by SFHDAG5NODE3.st.com (10.75.127.15) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 29 Apr 2019 12:03:37 +0200 Received: from SFHDAG5NODE1.st.com ([fe80::cc53:528c:36c8:95f6]) by SFHDAG5NODE1.st.com ([fe80::cc53:528c:36c8:95f6%20]) with mapi id 15.00.1347.000; Mon, 29 Apr 2019 12:03:36 +0200 From: Gerald BAEZA To: "will.deacon@arm.com" , "mark.rutland@arm.com" , "robh+dt@kernel.org" , "mcoquelin.stm32@gmail.com" , Alexandre TORGUE , "corbet@lwn.net" , "linux@armlinux.org.uk" , "olof@lixom.net" , "horms+renesas@verge.net.au" , "arnd@arndb.de" Subject: [PATCH 1/5] Documentation: perf: stm32: ddrperfm support Thread-Topic: [PATCH 1/5] Documentation: perf: stm32: ddrperfm support Thread-Index: AQHU/nLPEHho1416oEiblCko4nynGA== Date: Mon, 29 Apr 2019 10:03:36 +0000 Message-ID: <1556532194-27904-2-git-send-email-gerald.baeza@st.com> References: <1556532194-27904-1-git-send-email-gerald.baeza@st.com> In-Reply-To: <1556532194-27904-1-git-send-email-gerald.baeza@st.com> Accept-Language: fr-FR, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-messagesentrepresentingtype: 1 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.75.127.51] MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-04-29_05:, , signatures=0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190429_030344_810214_1BAD358E X-CRM114-Status: GOOD ( 15.60 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "devicetree@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Gerald BAEZA , "linux-stm32@st-md-mailman.stormreply.com" , "linux-arm-kernel@lists.infradead.org" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP The DDRPERFM is the DDR Performance Monitor embedded in STM32MP1 SOC. This documentation introduces the DDRPERFM, the stm32-ddr-pmu driver supporting it and how to use it with the perf tool. Signed-off-by: Gerald Baeza --- Documentation/perf/stm32-ddr-pmu.txt | 41 ++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 Documentation/perf/stm32-ddr-pmu.txt diff --git a/Documentation/perf/stm32-ddr-pmu.txt b/Documentation/perf/stm32-ddr-pmu.txt new file mode 100644 index 0000000..d5b35b3 --- /dev/null +++ b/Documentation/perf/stm32-ddr-pmu.txt @@ -0,0 +1,41 @@ +STM32 DDR Performance Monitor (DDRPERFM) +======================================== + +The DDRPERFM is the DDR Performance Monitor embedded in STM32MP1 SOC. +See STM32MP157 reference manual RM0436 to get a description of this peripheral. + + +The five following counters are supported by stm32-ddr-pmu driver: + cnt0: read operations counters (read_cnt) + cnt1: write operations counters (write_cnt) + cnt2: active state counters (activate_cnt) + cnt3: idle state counters (idle_cnt) + tcnt: time count, present for all sets (time_cnt) + +The stm32-ddr-pmu driver relies on the perf PMU framework to expose the +counters via sysfs: + $ ls /sys/bus/event_source/devices/ddrperfm/events + activate_cnt idle_cnt read_cnt time_cnt write_cnt + + +The perf PMU framework is usually invoked via the 'perf stat' tool. + +The DDRPERFM is a system monitor that cannot isolate the traffic coming from a +given thread or CPU, that is why stm32-ddr-pmu driver rejects any 'perf stat' +call that does not request a system-wide collection: the '-a, --all-cpus' +option is mandatory! + +Example: + $ perf stat -e ddrperfm/read_cnt/,ddrperfm/time_cnt/ -a sleep 20 + Performance counter stats for 'system wide': + + 342541560 ddrperfm/read_cnt/ + 10660011400 ddrperfm/time_cnt/ + + 20.021068551 seconds time elapsed + + +The driver also exposes a 'bandwidth' attribute that can be used to display +the read/write/total bandwidth achieved during the last 'perf stat' execution. + $ cat /sys/bus/event_source/devices/ddrperfm/bandwidth + Read = 403, Write = 239, Read & Write = 642 (MB/s)