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@@ -13,6 +13,10 @@ to be leveraged by platform firmware with minimal overhead to integrate PRM func
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formal design and is not validated at product quality. The development of this feature is shared in the edk2-staging
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branch to simplify collaboration by allowing direct code contributions and early feedback throughout its development.
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+> **Use recent edk2/master** - This code makes use of a very recent change in edk2 BaseTools. Specifically, commit
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+[b65afdd](https://github.com/tianocore/edk2/commit/b65afdde74d6c1fac1cdbd2efdad23ba26295808). Ensure you have that
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+change to build the code in this repo as-is.
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+
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> By default, the build makes use of a new ACPI OperationRegion type specifically introduced for PRM called
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`PlatformRtMechanism`. Support for this OperationRegion is planned for the next release of the ACPI specification.
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However, support for `PlatformRtMechanism` is already included in the iASL Compiler/Disassembler for early prototyping
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@@ -100,14 +104,21 @@ The following list are the currently defined build flags (if any) that may be pa
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### PRM Platform GUID
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**IMPORTANT**
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-A configuration item that requires user attention is the PRM platform GUID. Each platform that uses PRM must be
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-uniquely identifiable so that various instances of a PRM module can target the correct platform in PRM module updates.
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+PRM has a concept of a "Platform GUID" which associates a specific platform with a set of PRM modules built for
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+that platform. This GUID is used to ensure system compatibility for a given collection of PRM modules.
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+
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+Therefore, each PRM module must only target a single platform and each platform must have a unique GUID. Even if a
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+PRM module is unchanged between two different platforms now, there is no guarantee that will remain the case so always
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+assign a unique Platform GUID for each platform.
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-To apply a unique platform GUID set the following PCD to a unique value in your platform DSC file.
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- ``gPrmPkgTokenSpaceGuid.PcdPrmPlatformGuid``
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+The PRM Platform GUID is primarily used during PRM module runtime updates in the OS to ensure that the Platform GUID
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+in the system's ACPI table (PRMT) matches the Platform GUID of the module requested for update. Even if runtime
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+updates are not a planned feature for a given platform, still assign a unique Platform GUID for binary module
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+identification (the Platform GUID is in the module's export descriptor) and to ensure such updates can be seamlessly
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+supported in the future if needed.
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-The default value assigned in [PrmPkg.dec](PrmPkg/PrmPkg.dec) is zero. By design, this is an invalid value that will
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-cause an ASSERT if it is not updated.
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+In the `PrmPkg` implementation, the Platform GUID is automatically derived from the PLATFORM_GUID in the DSC file of
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+the package being built.
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## Overview
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At a high-level, PRM can be viewed from three levels of granularity:
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