From patchwork Mon Mar 9 15:16:38 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lina Iyer X-Patchwork-Id: 5968891 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 650499F380 for ; Mon, 9 Mar 2015 15:21:05 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 765652018E for ; Mon, 9 Mar 2015 15:21:04 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7BD292013A for ; Mon, 9 Mar 2015 15:21:03 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1YUzRw-0007vg-MY; Mon, 09 Mar 2015 15:18:32 +0000 Received: from mail-pa0-f44.google.com ([209.85.220.44]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1YUzR8-0007SN-Qw for linux-arm-kernel@lists.infradead.org; Mon, 09 Mar 2015 15:17:44 +0000 Received: by paceu11 with SMTP id eu11so59439892pac.1 for ; Mon, 09 Mar 2015 08:17:23 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=hquBdoaFN826pH+qyoPVdnxZsKHOd7f4d2333BKSU94=; b=Ss3Y9P8CIFSmqJkFN29azkDkyzoXxc9HYEuKXY2zrMOec1+nDVMndE+0cwVRXIP5j8 TDfz7ZCPVexkp277Sr1+V3xFbxdL8zp11+lDtsx4pudfo/snh0luqKWvYW6t9dOQPpMq l8kOd0GujhV4Ic9ODM1JESkZF9qE7yzYcEM8hBpiehzmGDHzoRdnsUUBXuLKS+MvBOqQ PECZRA1AfoFiI7q012Hdf0C/i/ImHBFeN9elU4FFc/Vhjw2djJNPKl72OqJu2c6z3zu3 OFvs3Xs4A6UqKuVCUmfLctKodHnv1u/R98p+QWEc9KqHzSwAtRRkzyv+yNkoYjEXuvkL AiDw== X-Gm-Message-State: ALoCoQm0zgiqJGRneuu3NXwGQ0tnW0pI1wwzEGb8UgNk9uea0QbbYDUXqMSSBIHi6+skcnFXdGxO X-Received: by 10.70.18.97 with SMTP id v1mr26754905pdd.152.1425914243449; Mon, 09 Mar 2015 08:17:23 -0700 (PDT) Received: from ubuntu.localdomain (i-global254.qualcomm.com. [199.106.103.254]) by mx.google.com with ESMTPSA id pm9sm6639462pdb.59.2015.03.09.08.17.21 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 09 Mar 2015 08:17:22 -0700 (PDT) From: Lina Iyer To: daniel.lezcano@linaro.org, khilman@linaro.org, sboyd@codeaurora.org, galak@codeaurora.org, linux-arm-msm@vger.kernel.org, linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v15 03/11] ARM: cpuidle: qcom: Add documentation for qcom cpuidle states. Date: Mon, 9 Mar 2015 09:16:38 -0600 Message-Id: <1425914206-22295-4-git-send-email-lina.iyer@linaro.org> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1425914206-22295-1-git-send-email-lina.iyer@linaro.org> References: <1425914206-22295-1-git-send-email-lina.iyer@linaro.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150309_081742_941134_AD1F4198 X-CRM114-Status: GOOD ( 17.14 ) X-Spam-Score: -0.7 (/) Cc: msivasub@codeaurora.org, devicetree@vger.kernel.org, lorenzo.pieralisi@arm.com, Lina Iyer X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Add documentation for cpuidle states of QCOM cpus. In addition to arm-idle-state compatible string, the ARM idle state definition must define one of the following compatible strings - "qcom,idle-state-stby", "qcom,idle-state-ret", "qcom,idle-state-spc", "qcom,idle-state-pc", The compatibles helps the SPM platform driver to use the correct idle function when the index to the idle state is passed to the platform driver. Signed-off-by: Lina Iyer --- .../bindings/arm/msm/qcom,idle-state.txt | 81 ++++++++++++++++++++++ 1 file changed, 81 insertions(+) create mode 100644 Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt diff --git a/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt b/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt new file mode 100644 index 0000000..ae1b07f --- /dev/null +++ b/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt @@ -0,0 +1,81 @@ +QCOM Idle States for cpuidle driver + +ARM provides idle-state node to define the cpuidle states, as defined in [1]. +cpuidle-qcom is the cpuidle driver for Qualcomm SoCs and uses these idle +states. Idle states have different enter/exit latency and residency values. +The idle states supported by the QCOM SoC are defined as - + + * Standby + * Retention + * Standalone Power Collapse (Standalone PC or SPC) + * Power Collapse (PC) + +Standby: Standby does a little more in addition to architectural clock gating. +When the WFI instruction is executed the ARM core would gate its internal +clocks. In addition to gating the clocks, QCOM cpus use this instruction as a +trigger to execute the SPM state machine. The SPM state machine waits for the +interrupt to trigger the core back in to active. This triggers the cache +hierarchy to enter standby states, when all cpus are idle. An interrupt brings +the SPM state machine out of its wait, the next step is to ensure that the +cache hierarchy is also out of standby, and then the cpu is allowed to resume +execution. + +Retention: Retention is a low power state where the core is clock gated and +the memory and the registers associated with the core are retained. The +voltage may be reduced to the minimum value needed to keep the processor +registers active. The SPM should be configured to execute the retention +sequence and would wait for interrupt, before restoring the cpu to execution +state. Retention may have a slightly higher latency than Standby. + +Standalone PC: A cpu can power down and warmboot if there is a sufficient time +between the time it enters idle and the next known wake up. SPC mode is used +to indicate a core entering a power down state without consulting any other +cpu or the system resources. This helps save power only on that core. The SPM +sequence for this idle state is programmed to power down the supply to the +core, wait for the interrupt, restore power to the core, and ensure the +system state including cache hierarchy is ready before allowing core to +resume. Applying power and resetting the core causes the core to warmboot +back into Elevation Level (EL) which trampolines the control back to the +kernel. Entering a power down state for the cpu, needs to be done by trapping +into a EL. Failing to do so, would result in a crash enforced by the warm boot +code in the EL for the SoC. On SoCs with write-back L1 cache, the cache has to +be flushed in s/w, before powering down the core. + +Power Collapse: This state is similar to the SPC mode, but distinguishes +itself in that the cpu acknowledges and permits the SoC to enter deeper sleep +modes. In a hierarchical power domain SoC, this means L2 and other caches can +be flushed, system bus, clocks - lowered, and SoC main XO clock gated and +voltages reduced, provided all cpus enter this state. Since the span of low +power modes possible at this state is vast, the exit latency and the residency +of this low power mode would be considered high even though at a cpu level, +this essentially is cpu power down. The SPM in this state also may handshake +with the Resource power manager processor in the SoC to indicate a complete +application processor subsystem shut down. + +The idle-state for QCOM SoCs are distinguished by the compatible property of +the idle-states device node. +The devicetree representation of the idle state should be - + +Required properties: + +- compatible: Must be one of - + "qcom,idle-state-stby", + "qcom,idle-state-ret", + "qcom,idle-state-spc", + "qcom,idle-state-pc", + and "arm,idle-state". + +Other required and optional properties are specified in [1]. + +Example: + + idle-states { + CPU_SPC: spc { + compatible = "qcom,idle-state-spc", "arm,idle-state"; + entry-latency-us = <150>; + exit-latency-us = <200>; + min-residency-us = <2000>; + }; + }; + +[1]. Documentation/devicetree/bindings/arm/idle-states.txt