From patchwork Tue Apr 16 02:55:54 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mauro Carvalho Chehab X-Patchwork-Id: 10901813 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C0E201390 for ; Tue, 16 Apr 2019 02:56:58 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A26432894D for ; Tue, 16 Apr 2019 02:56:58 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9635228956; Tue, 16 Apr 2019 02:56:58 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id C21DD2894D for ; Tue, 16 Apr 2019 02:56:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=ZMSUBkfd+OREUwnzgol34OhTZLZZi1LEnORUxwWsMV0=; b=V0zhp8YuiCmVMw EhlSvZDliVv+GNJphtBULsYat4U6gIx4dXG4ENBxLoea6fJj7uSdqM788zLoGBgsZu5hxhcMhgmr3 7os0kyOelLwSN98VeEoKkIEgy80czV5kpAU4CXJlg/piXXUwZog9U6s4VciI14G2o+1L2mF0jW50o CKb2raX5Uu2cNUrlwlh6JR0RmFA2d0CADC3wfSivAn3ZFRwA0PrS5nGjNYGgx8HmzzFXeGPKXjWa8 Lzil/wCx6u8lpuUaTh37gMWsj7NKBmw5wPvL1OONKn2PYbFmZtxHzTRfdf2UrmgnvY08Q1T23FM6E lceRM3qBS4aEbtjEx2tw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hGEHE-000822-7f; Tue, 16 Apr 2019 02:56:52 +0000 Received: from 177.205.118.176.dynamic.adsl.gvt.net.br ([177.205.118.176] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hGEGu-0007ak-Qy; Tue, 16 Apr 2019 02:56:33 +0000 Received: from mchehab by bombadil.infradead.org with local (Exim 4.92) (envelope-from ) id 1hGEGn-0001o7-M4; Mon, 15 Apr 2019 23:56:25 -0300 From: Mauro Carvalho Chehab To: Linux Doc Mailing List Subject: [PATCH 29/57] docs: riscv: convert it to ReST format Date: Mon, 15 Apr 2019 23:55:54 -0300 Message-Id: X-Mailer: git-send-email 2.20.1 In-Reply-To: References: MIME-Version: 1.0 X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Albert Ou , Jonathan Corbet , Palmer Dabbelt , linux-kernel@vger.kernel.org, Mauro Carvalho Chehab , Mauro Carvalho Chehab , linux-riscv@lists.infradead.org Sender: "linux-riscv" Errors-To: linux-riscv-bounces+patchwork-linux-riscv=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP The conversion here is trivial: - Adjust the document title's markup - Do some whitespace alignment; - mark literal blocks; - Use ReST way to markup indented lists. Signed-off-by: Mauro Carvalho Chehab --- Documentation/riscv/pmu.txt | 98 ++++++++++++++++++++----------------- 1 file changed, 52 insertions(+), 46 deletions(-) diff --git a/Documentation/riscv/pmu.txt b/Documentation/riscv/pmu.txt index b29f03a6d82f..acb216b99c26 100644 --- a/Documentation/riscv/pmu.txt +++ b/Documentation/riscv/pmu.txt @@ -1,5 +1,7 @@ +=================================== Supporting PMUs on RISC-V platforms -========================================== +=================================== + Alan Kao , Mar 2018 Introduction @@ -77,13 +79,13 @@ Note that some features can be done in this stage as well: (2) privilege level setting (user space only, kernel space only, both); (3) destructor setting. Normally it is sufficient to apply *riscv_destroy_event*; (4) tweaks for non-sampling events, which will be utilized by functions such as -*perf_adjust_period*, usually something like the follows: + *perf_adjust_period*, usually something like the follows:: -if (!is_sampling_event(event)) { - hwc->sample_period = x86_pmu.max_period; - hwc->last_period = hwc->sample_period; - local64_set(&hwc->period_left, hwc->sample_period); -} + if (!is_sampling_event(event)) { + hwc->sample_period = x86_pmu.max_period; + hwc->last_period = hwc->sample_period; + local64_set(&hwc->period_left, hwc->sample_period); + } In the case of *riscv_base_pmu*, only (3) is provided for now. @@ -94,10 +96,10 @@ In the case of *riscv_base_pmu*, only (3) is provided for now. 3.1. Interrupt Initialization This often occurs at the beginning of the *event_init* method. In common -practice, this should be a code segment like +practice, this should be a code segment like:: -int x86_reserve_hardware(void) -{ + int x86_reserve_hardware(void) + { int err = 0; if (!atomic_inc_not_zero(&pmc_refcount)) { @@ -114,7 +116,7 @@ int x86_reserve_hardware(void) } return err; -} + } And the magic is in *reserve_pmc_hardware*, which usually does atomic operations to make implemented IRQ accessible from some global function pointer. @@ -128,28 +130,28 @@ which will be introduced in the next section.) 3.2. IRQ Structure -Basically, a IRQ runs the following pseudo code: +Basically, a IRQ runs the following pseudo code:: -for each hardware counter that triggered this overflow + for each hardware counter that triggered this overflow - get the event of this counter + get the event of this counter - // following two steps are defined as *read()*, - // check the section Reading/Writing Counters for details. - count the delta value since previous interrupt - update the event->count (# event occurs) by adding delta, and - event->hw.period_left by subtracting delta + // following two steps are defined as *read()*, + // check the section Reading/Writing Counters for details. + count the delta value since previous interrupt + update the event->count (# event occurs) by adding delta, and + event->hw.period_left by subtracting delta - if the event overflows - sample data - set the counter appropriately for the next overflow + if the event overflows + sample data + set the counter appropriately for the next overflow - if the event overflows again - too frequently, throttle this event - fi - fi + if the event overflows again + too frequently, throttle this event + fi + fi -end for + end for However as of this writing, none of the RISC-V implementations have designed an interrupt for perf, so the details are to be completed in the future. @@ -195,23 +197,26 @@ A normal flow of these state transitions are as follows: At this stage, a general event is bound to a physical counter, if any. The state changes to PERF_HES_STOPPED and PERF_HES_UPTODATE, because it is now stopped, and the (software) event count does not need updating. -** *start* is then called, and the counter is enabled. - With flag PERF_EF_RELOAD, it writes an appropriate value to the counter (check - previous section for detail). - Nothing is written if the flag does not contain PERF_EF_RELOAD. - The state now is reset to none, because it is neither stopped nor updated - (the counting already started) + + - *start* is then called, and the counter is enabled. + With flag PERF_EF_RELOAD, it writes an appropriate value to the counter (check + previous section for detail). + Nothing is written if the flag does not contain PERF_EF_RELOAD. + The state now is reset to none, because it is neither stopped nor updated + (the counting already started) + * When being context-switched out, *del* is called. It then checks out all the events in the PMU and calls *stop* to update their counts. -** *stop* is called by *del* - and the perf core with flag PERF_EF_UPDATE, and it often shares the same - subroutine as *read* with the same logic. - The state changes to PERF_HES_STOPPED and PERF_HES_UPTODATE, again. -** Life cycle of these two pairs: *add* and *del* are called repeatedly as - tasks switch in-and-out; *start* and *stop* is also called when the perf core - needs a quick stop-and-start, for instance, when the interrupt period is being - adjusted. + - *stop* is called by *del* + and the perf core with flag PERF_EF_UPDATE, and it often shares the same + subroutine as *read* with the same logic. + The state changes to PERF_HES_STOPPED and PERF_HES_UPTODATE, again. + + - Life cycle of these two pairs: *add* and *del* are called repeatedly as + tasks switch in-and-out; *start* and *stop* is also called when the perf core + needs a quick stop-and-start, for instance, when the interrupt period is being + adjusted. Current implementation is sufficient for now and can be easily extended to features in the future. @@ -225,25 +230,26 @@ A. Related Structures Both structures are designed to be read-only. *struct pmu* defines some function pointer interfaces, and most of them take -*struct perf_event* as a main argument, dealing with perf events according to -perf's internal state machine (check kernel/events/core.c for details). + *struct perf_event* as a main argument, dealing with perf events according to + perf's internal state machine (check kernel/events/core.c for details). *struct riscv_pmu* defines PMU-specific parameters. The naming follows the -convention of all other architectures. + convention of all other architectures. * struct perf_event: include/linux/perf_event.h * struct hw_perf_event The generic structure that represents perf events, and the hardware-related -details. + details. * struct riscv_hw_events: arch/riscv/include/asm/perf_event.h The structure that holds the status of events, has two fixed members: -the number of events and the array of the events. + the number of events and the array of the events. References ---------- [1] https://github.com/riscv/riscv-linux/pull/124 + [2] https://groups.google.com/a/groups.riscv.org/forum/#!topic/sw-dev/f19TmCNP6yA