From patchwork Mon Aug 4 15:28:25 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hanjun Guo X-Patchwork-Id: 34876 Return-Path: X-Original-To: linaro@patches.linaro.org Delivered-To: linaro@patches.linaro.org Received: from mail-pd0-f200.google.com (mail-pd0-f200.google.com [209.85.192.200]) by ip-10-151-82-157.ec2.internal (Postfix) with ESMTPS id 655A921F5F for ; Mon, 4 Aug 2014 15:32:28 +0000 (UTC) Received: by mail-pd0-f200.google.com with SMTP id w10sf45811829pde.7 for ; Mon, 04 Aug 2014 08:32:27 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:delivered-to:from:to:cc:subject :date:message-id:in-reply-to:references:sender:precedence:list-id :x-original-sender:x-original-authentication-results:mailing-list :list-post:list-help:list-archive:list-unsubscribe; bh=XmCvBnsOBhqNT16mjdyuP9mGdLMM1DEHAy263hVOun4=; b=cPO1wfriqHaeJ75D3euQIhWHXKdxAWa9pb4LmjsUszZSuWEqVc6kQJbYL6PMGv09Gv KxDQubjz4Uh7rCusdxpgAgH1kaNGUDMyL8SQK9H6/a9m9anTG1YSYL0Y+XRGNla/YLN1 l5v3T3H3L2sgBNYjpSXelvYkjB1M4LJoF3Qv1CRKm5bGKuFf8CXLc2AoOoM6+s5uuCU+ NWDQWH+qfveoz5PAzyAJGEqmxCoBqTKWrZ+/dKjDd+c136UHs0HdJq8yfGgqokL9ILK5 6k5UNFbgHnXfhKYK7YvJMfQD7jVknJH8ayFh+CYUkHM8rZciTlAgorbCub5s3PdNuV2p HjgQ== X-Gm-Message-State: ALoCoQldIrcUWi+pzvNVpVundzfQSxOms/qr+nYRY3EByJsz7TDfxg8Ljq1LShUPoCeRhCikdgR9 X-Received: by 10.67.5.228 with SMTP id cp4mr9210728pad.8.1407166347692; Mon, 04 Aug 2014 08:32:27 -0700 (PDT) MIME-Version: 1.0 X-BeenThere: patchwork-forward@linaro.org Received: by 10.140.87.37 with SMTP id q34ls939255qgd.5.gmail; Mon, 04 Aug 2014 08:32:27 -0700 (PDT) X-Received: by 10.52.137.2 with SMTP id qe2mr20666253vdb.11.1407166347581; Mon, 04 Aug 2014 08:32:27 -0700 (PDT) Received: from mail-vc0-f169.google.com (mail-vc0-f169.google.com [209.85.220.169]) by mx.google.com with ESMTPS id xv9si12189867vdb.0.2014.08.04.08.32.26 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 04 Aug 2014 08:32:26 -0700 (PDT) Received-SPF: pass (google.com: domain of patch+caf_=patchwork-forward=linaro.org@linaro.org designates 209.85.220.169 as permitted sender) client-ip=209.85.220.169; Received: by mail-vc0-f169.google.com with SMTP id le20so11458832vcb.28 for ; Mon, 04 Aug 2014 08:32:26 -0700 (PDT) X-Received: by 10.52.120.38 with SMTP id kz6mr1776682vdb.86.1407166346335; Mon, 04 Aug 2014 08:32:26 -0700 (PDT) X-Forwarded-To: patchwork-forward@linaro.org X-Forwarded-For: patch@linaro.org patchwork-forward@linaro.org Delivered-To: patch@linaro.org Received: by 10.221.37.5 with SMTP id tc5csp313497vcb; Mon, 4 Aug 2014 08:32:25 -0700 (PDT) X-Received: by 10.69.20.11 with SMTP id gy11mr24777312pbd.28.1407166344816; Mon, 04 Aug 2014 08:32:24 -0700 (PDT) Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id 4si9001654pdm.284.2014.08.04.08.32.24 for ; Mon, 04 Aug 2014 08:32:24 -0700 (PDT) Received-SPF: none (google.com: linux-kernel-owner@vger.kernel.org does not designate permitted sender hosts) client-ip=209.132.180.67; Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753312AbaHDPcN (ORCPT + 21 others); Mon, 4 Aug 2014 11:32:13 -0400 Received: from mail-pa0-f41.google.com ([209.85.220.41]:54942 "EHLO mail-pa0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752794AbaHDPcI (ORCPT ); Mon, 4 Aug 2014 11:32:08 -0400 Received: by mail-pa0-f41.google.com with SMTP id rd3so10210024pab.28 for ; Mon, 04 Aug 2014 08:32:07 -0700 (PDT) X-Received: by 10.68.230.194 with SMTP id ta2mr24581370pbc.51.1407166327797; Mon, 04 Aug 2014 08:32:07 -0700 (PDT) Received: from localhost ([39.182.20.233]) by mx.google.com with ESMTPSA id kl7sm27241656pdb.13.2014.08.04.08.32.00 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Mon, 04 Aug 2014 08:32:07 -0700 (PDT) From: Hanjun Guo To: Catalin Marinas , "Rafael J. Wysocki" , Mark Rutland Cc: Graeme Gregory , Arnd Bergmann , Olof Johansson , Grant Likely , Sudeep Holla , Will Deacon , Jason Cooper , Marc Zyngier , Bjorn Helgaas , Daniel Lezcano , Mark Brown , Rob Herring , Robert Richter , Lv Zheng , Robert Moore , Lorenzo Pieralisi , Liviu Dudau , Randy Dunlap , Charles.Garcia-Tobin@arm.com, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linaro-acpi@lists.linaro.org, Hanjun Guo Subject: [PATCH v2 18/18] Documentation: ACPI for ARM64 Date: Mon, 4 Aug 2014 23:28:25 +0800 Message-Id: <1407166105-17675-19-git-send-email-hanjun.guo@linaro.org> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1407166105-17675-1-git-send-email-hanjun.guo@linaro.org> References: <1407166105-17675-1-git-send-email-hanjun.guo@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: list List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Removed-Original-Auth: Dkim didn't pass. X-Original-Sender: hanjun.guo@linaro.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of patch+caf_=patchwork-forward=linaro.org@linaro.org designates 209.85.220.169 as permitted sender) smtp.mail=patch+caf_=patchwork-forward=linaro.org@linaro.org Mailing-list: list patchwork-forward@linaro.org; contact patchwork-forward+owners@linaro.org X-Google-Group-Id: 836684582541 List-Post: , List-Help: , List-Archive: List-Unsubscribe: , From: Graeme Gregory Add documentation for the guidelines of how to use ACPI on ARM64. Signed-off-by: Graeme Gregory Signed-off-by: Hanjun Guo --- Documentation/arm64/arm-acpi.txt | 215 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 215 insertions(+) create mode 100644 Documentation/arm64/arm-acpi.txt diff --git a/Documentation/arm64/arm-acpi.txt b/Documentation/arm64/arm-acpi.txt new file mode 100644 index 0000000..a6e14a2 --- /dev/null +++ b/Documentation/arm64/arm-acpi.txt @@ -0,0 +1,215 @@ +ACPI on ARMv8 Servers +--------------------- + +ACPI can be used for ARMv8 general purpose servers designed to follow +the SBSA specification (currently available to people with an ARM login at +http://silver.arm.com). + +The kernel will implement minimum ACPI version is 5.1 + errata as released by +the UEFI Forum, which is available at . + +If the machine does not meet the requirements of the SBSA, or cannot be +described in the required ACPI specifications then it is likely that Device Tree +(DT) is more suitable for the hardware. + +Relationship with Device Tree +----------------------------- + +ACPI support in drivers and subsystems for ARMv8 should never be mutually +exclusive with DT support at compile time. + +At boot time the kernel will only use one description method depending on +parameters passed from the bootloader (including kernel bootargs). + +Regardless of whether DT or ACPI is used, the kernel must always be capable +of booting with either scheme (in kernels with both schemes enabled at compile +time). + +When booting using ACPI tables the /chosen node in DT will still be parsed +to extract the kernel command line and initrd path. No other section of +the DT will be used. + +Booting using ACPI tables +------------------------- + +Currently, the only defined method to pass ACPI tables to the kernel on ARMv8 +is via the UEFI system configuration table. + +The UEFI implementation MUST set the ACPI_20_TABLE_GUID to point to the +RSDP table (the table with the ACPI signature "RSD PTR "). + +The pointer to the RSDP table will be retrieved from EFI by the ACPI core. + +Processing of ACPI tables may be disabled by passing acpi=off on the kernel +command line. + +DO use an XSDT; RSDTs are deprecated and should not be used on arm64. They +only allow for 32-bit addresses. + +DO NOT use the 32-bit address fields in the FADT; they are deprecated. The +64-bit alternatives MUST be used. + +The minimum set of tables MUST include RSDP, XSDT, FACS, FADT, DSDT, MADT +and GTDT. If PCI is used the MCFG table MUST also be present. + +ACPI Detection +-------------- + +Drivers should determine their probe() type by checking for ACPI_HANDLE, +or .of_node, or other information in the device structure. This is +detailed further in the "Driver Recommendations" section. + +In non-driver code If the presence of ACPI needs to be detected at runtime, +then check the value of acpi_disabled. If CONFIG_ACPI not being set, +acpi_disabled will always be 1. + +Device Enumeration +------------------ + +Device descriptions in ACPI should use standard recognized ACPI interfaces. +These are far simpler than the information provided via Device Tree. Drivers +should take into account this simplicity and work with sensible defaults. + +On no account should a Device Tree attempt to be replicated in ASL using such +constructs as Name(KEY0, "Value1") type constructs. Additional driver specific +data should be passed in the appropriate _DSM (ACPI Section 9.14.1) method or +_DSD (ACPI Section 6.2.5). + +This data should be rare and not OS specific. For x86 ACPI has taken to +identifying itself as Windows because it was found that only one path was +routinely tested. For ARMv8 it would be preferable to have only one well +tested path. + +_DSD covers more than the generic server case and care should be taken not to +replicate highly specific embedded behaviour from DT into generic servers. + +Common _DSD bindings should be submitted to ASWG to be included in the +document :- + +http://www.uefi.org/sites/default/files/resources/_DSD-implementation-guide-toplevel.htm + +If these bindings are mirrored from DT care should be taken to ensure they are +reviewed as DT bindings before submission to limit divergance in bindings. + +Programmable Power Control Resources +------------------------------------ + +Programmable power control resources include such resources as voltage/current +providers (regulators) and clock sources. + +For power control of these resources they should be represented with Power +Resource Objects (ACPI Section 7.1). The ACPI core will then handle correctly +enabling/disabling of resources as they are needed. + +The ACPI 5.1 specification does not contain any standard binding for these +objects to enable programmable levels or rates so this should be avoided if +possible and the resources set to appropriate levels by the firmware. If this is +not possible then any manipulation should be abstracted in ASL. + +Each device in ACPI has D-states and these can be controlled through +the optional methods _PS0..._PS3 where _PS0 is full on and _PS3 is full off. + +If either _PS0 or _PS3 is implemented, then the other method must also be +implemented. + +If a device requires usage or setup of a power resource when on, the ASL +should organize that it is allocated/enabled using the _PS0 method. + +Resources allocated/enabled in the _PS0 method should be disabled/de-allocated +in the _PS3 method. + +Such code in _PS? methods will of course be very platform specific but +should allow the driver to operate the device without special non-standard +values being read from ASL. Further, abstracting the use of these resources +allows hardware revisions without requiring updates to the kernel. + +Clocks +------ + +Like clocks that are part of the power resources there is no standard way +to represent a clock tree in ACPI 5.1 in a similar manner to how it is +described in DT. + +Devices affected by this include things like UARTs, SoC driven LCD displays, +etc. + +The firmware (for example, UEFI) should initialize these clocks to fixed working +values before the kernel is executed. + +Driver Recommendations +---------------------- + +DO NOT remove any FDT handling when adding ACPI support for a driver. Different +systems may use the same device. + +DO try and keep complex sections of ACPI and DT functionality separate. This +may mean a patch to break out some complex DT to another function before +the patch to add ACPI. This may happen in other functions but is most likely +in probe function. This gives a clearer flow of data for reviewing driver +source. + +probe() :- + +static int device_probe_dt(struct platform_device *pdev) +{ + /* DT specific functionality */ + ... +} + +static int device_probe_acpi(struct platform_device *pdev) +{ + /* ACPI specific functionality */ + ... +} + +static int device_probe(stuct platform_device *pdev) +{ + ... + struct device_node node = pdev->dev.of_node; + ... + + if (node) + ret = device_probe_dt(pdev); + else if (ACPI_HANDLE(&pdev->dev)) + ret = device_probe_acpi(pdev); + else + /* other initialization */ + ... + /* Continue with any generic probe operations */ + ... +} + +DO keep the MODULE_DEVICE_TABLE entries together in the driver to make it clear +the different names the driver is probed for, both from DT and from ACPI. + +module device tables :- + +static struct of_device_id virtio_mmio_match[] = { + { .compatible = "virtio,mmio", }, + { } +}; +MODULE_DEVICE_TABLE(of, virtio_mmio_match); + +static const struct acpi_device_id virtio_mmio_acpi_match[] = { + { "LNRO0005", }, + { } +}; +MODULE_DEVICE_TABLE(acpi, virtio_mmio_acpi_match); + +ASWG +---- + +The following areas are not yet well defined for ARM in the current ACPI +specification and are expected to be worked through in the UEFI ACPI +Specification Working Group (ASWG) . +Participation in this group is open to all UEFI members. + + - ACPI based CPU topology + - ACPI based Power management + - CPU idle control based on PSCI + - CPU performance control (CPPC) + +No code shall be accepted into the kernel unless it complies with the released +standards from UEFI ASWG. If there are features missing from ACPI to make it +function on a platform, ECRs should be submitted to ASWG and go through the +approval process.