From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hanjun Guo Subject: Re: [PATCH v6 17/17] Documentation: ACPI for ARM64 Date: Wed, 21 Jan 2015 20:37:00 +0800 Message-ID: <54BF9D6C.7020807@linaro.org> References: <1420368918-5086-1-git-send-email-hanjun.guo@linaro.org> <1420368918-5086-18-git-send-email-hanjun.guo@linaro.org> <20150119203328.GB3766@cbox> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-pa0-f49.google.com ([209.85.220.49]:34695 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752105AbbAUMhP (ORCPT ); Wed, 21 Jan 2015 07:37:15 -0500 Received: by mail-pa0-f49.google.com with SMTP id fa1so1046639pad.8 for ; Wed, 21 Jan 2015 04:37:14 -0800 (PST) In-Reply-To: <20150119203328.GB3766@cbox> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Christoffer Dall Cc: Catalin Marinas , "Rafael J. Wysocki" , Olof Johansson , Arnd Bergmann , Mark Rutland , Grant Likely , Will Deacon , Rob Herring , Lorenzo Pieralisi , Robert Richter , Jason Cooper , Graeme Gregory , linaro-acpi@lists.linaro.org, Marc Zyngier , Jon Masters , Timur Tabi , Randy Dunlap , linux-kernel@vger.kernel.org, Al Stone , linux-acpi@vger.kernel.org, Mark Brown , suravee.suthikulpanit@amd.com, Sudeep Holla , Bjorn Helgaas , phoenix.liyi@huawei.coml Hi Christoffer, Sorry for the late reply, I got no answer yet but with one question below. On 2015=E5=B9=B401=E6=9C=8820=E6=97=A5 04:33, Christoffer Dall wrote: > Hi, > > On Sun, Jan 04, 2015 at 06:55:18PM +0800, Hanjun Guo wrote: >> From: Graeme Gregory >> >> Add documentation for the guidelines of how to use ACPI >> on ARM64. >> >> Reviewed-by: Suravee Suthikulpanit >> Signed-off-by: Graeme Gregory >> Signed-off-by: Al Stone >> Signed-off-by: Hanjun Guo >> --- >> Documentation/arm64/arm-acpi.txt | 327 +++++++++++++++++++++++++++= ++++++++++++ >> 1 file changed, 327 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..21e7020 >> --- /dev/null >> +++ b/Documentation/arm64/arm-acpi.txt >> @@ -0,0 +1,327 @@ >> +ACPI on ARMv8 Servers >> +--------------------- >> +ACPI can be used for ARMv8 general purpose servers designed to foll= ow >> +the ARM SBSA (Server Base System Architecture) and SBBR (Server Bas= e >> +Boot Requirements) specifications, currently available to those wit= h >> +an ARM login at http://silver.arm.com. >> + >> +The ARMv8 kernel implements the reduced hardware model of ACPI vers= ion >> +5.1 and later. Links to the specification and all external documen= ts >> +it refers to are managed by the UEFI Forum. The specification is >> +available at http://www.uefi.org/specifications and external docume= nts >> +can be found via http://www.uefi.org/acpi. >> + >> +If an ARMv8 system does not meet the requirements of the SBSA, or c= annot >> +be described using the mechanisms defined in the required ACPI spec= ifications, >> +then it is likely that Device Tree (DT) is more suitable than ACPI = for the >> +hardware. >> + >> + >> +Relationship with Device Tree >> +----------------------------- >> +ACPI support in drivers and subsystems for ARMv8 should never be mu= tually >> +exclusive with DT support at compile time. >> + >> +At boot time the kernel will only use one description method depend= ing 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). >> + >> + >> +Booting using ACPI tables >> +------------------------- >> +The only defined method for passing ACPI tables to the kernel on AR= Mv8 >> +is via the UEFI system configuration table. >> + > > This is a bit concerning for the approach we are currently taking to > support ACPI on Xen [1]. > > Background: Xen is a tiny hypervisor which cannot parse the DSDT or a= ny > other non-static table. Xen relies on Linux in Dom0 to manage most > (basically everything except the GIC, serial port, SMMU, and timers) > hardware resources and relies on Dom0 to parse the ACPI tables. > > While Xen itself is typically booted by UEFI and finds RSDP through t= he > UEFI system table, Xen does NOT run another UEFI instance to boot Dom= 0 > nor does it pass through the presence of UEFI to Dom0 in any way. > Instead, it just created a DT (with modifications concerning the > hardware mentioned above) and boots Linux in Dom0 directly (on x86 an= y > required UEFI call is performed through paravirtualized hypercalls). > > In the case of ACPI, Xen adds a property to the chosen node and > populates it with the RDSP in Dom0's address space. Patches have not Sorry I'm not familiar with hypervisor, I have question here about x86 on xen, how ACPI works on XEN for x86? Thanks Hanjun -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html