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[209.132.180.67]) by mx.google.com with ESMTP id e15si1221947pdm.25.2014.09.12.07.03.02 for ; Fri, 12 Sep 2014 07:03:03 -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 S1755327AbaILOCX (ORCPT + 27 others); Fri, 12 Sep 2014 10:02:23 -0400 Received: from mail-pd0-f179.google.com ([209.85.192.179]:48257 "EHLO mail-pd0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755235AbaILOCT (ORCPT ); Fri, 12 Sep 2014 10:02:19 -0400 Received: by mail-pd0-f179.google.com with SMTP id g10so1289014pdj.38 for ; Fri, 12 Sep 2014 07:02:19 -0700 (PDT) X-Received: by 10.69.26.33 with SMTP id iv1mr12701983pbd.62.1410530537421; Fri, 12 Sep 2014 07:02:17 -0700 (PDT) Received: from localhost ([111.140.73.43]) by mx.google.com with ESMTPSA id fz10sm4038141pdb.50.2014.09.12.07.02.15 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Fri, 12 Sep 2014 07:02:16 -0700 (PDT) From: Hanjun Guo To: Catalin Marinas , "Rafael J. Wysocki" , Mark Rutland , Olof Johansson , Grant Likely , Will Deacon Cc: Graeme Gregory , Arnd Bergmann , Sudeep Holla , Jon Masters , 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 v4 18/18] Documentation: ACPI for ARM64 Date: Fri, 12 Sep 2014 22:00:16 +0800 Message-Id: <1410530416-30200-19-git-send-email-hanjun.guo@linaro.org> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1410530416-30200-1-git-send-email-hanjun.guo@linaro.org> References: <1410530416-30200-1-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 209.85.215.50 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 | 218 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 218 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..704a9e0 --- /dev/null +++ b/Documentation/arm64/arm-acpi.txt @@ -0,0 +1,218 @@ +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 is not 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 represented with the appropriate _DSD (ACPI Section 6.2.5) +structure. _DSM (ACPI Section 9.14.1) should only be used if _DSD cannot +represent the data required. + +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) + - ACPI based SMMU + - ITS support for GIC in MADT + +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.