[PATCH v2 1/3] Documentation: arm: add UEFI support documentation
From: Rob Herring <hidden>
Date: 2013-10-03 16:11:45
Also in:
linux-devicetree, linux-efi, lkml
Adding devicetree list since you are defining bindings... On 10/03/2013 06:24 AM, Leif Lindholm wrote:
quoted hunk ↗ jump to hunk
This patch provides documentation of the [U]EFI runtime services and configuration features. Cc: linux-doc at vger.kernel.org Signed-off-by: Leif Lindholm <redacted> Acked-by: Rob Landley <redacted> --- Documentation/arm/00-INDEX | 3 +++ Documentation/arm/uefi.txt | 47 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 50 insertions(+) create mode 100644 Documentation/arm/uefi.txtdiff --git a/Documentation/arm/00-INDEX b/Documentation/arm/00-INDEX index 4978456..87e01d1 100644 --- a/Documentation/arm/00-INDEX +++ b/Documentation/arm/00-INDEX@@ -36,3 +36,6 @@ nwfpe/ - NWFPE floating point emulator documentation swp_emulation - SWP/SWPB emulation handler/logging description + +uefi.txt + - [U]EFI configuration and runtime services documentationdiff --git a/Documentation/arm/uefi.txt b/Documentation/arm/uefi.txt new file mode 100644 index 0000000..e6e4d41 --- /dev/null +++ b/Documentation/arm/uefi.txt@@ -0,0 +1,47 @@ +UEFI, the Unified Extensible Firmware Interface is a speifcication +governing the behaviours of compatible firmware interfaces. It is +maintained by the UEFI Forum - http://www.uefi.org/. + +Since UEFI is an evolution of its predecessor 'EFI', the terms EFI and +UEFI are used somewhat interchangeably in this document and associated +source code. + +The implementation depends on receiving the UEFI runtime memory map and a +pointer to the System Table in a Flattened Device Tree - so is only available +with CONFIG_OF. + +It parses the FDT /chosen node for the following parameters:
DT bindings should be documented in Documentation/devicetree/bindings. I also wonder if this would be more appropriately placed in a /firmware node.
+- 'linux,efi-system-table': + Physical address of the system table. (required) + 64-bit value since an ARMv7 plattform may support LPAE, and to facilitate + code sharing with arm64. Top 32 bits will be ignored, since UEFI specification + mandates a 1:1 mapping of all RAM. +- 'linux,efi-mmap': + The EFI memory map as an embedded property. (required) + An array of type EFI_MEMORY_DESCRIPTOR as described by the UEFI + specification, current version described in Linux by efi_memory_desc_t.
Is that too complex to describe here?
+ The memory map is represented in little-endian, not DT, byte order. + This map needs to contain at least the regions to be preserved for runtime + services, but would normally just be the map retreieved by calling UEFI + GetMemoryMap() immediately before ExitBootServices(). +- 'linux,efi-mmap-desc-size': + Size of each descriptor in the memory map. (override default)
32-bit value?
+- 'linux,efi-mmap-desc-ver': + Memory descriptor format version. (override default)
String? Number? Are these all generated by UEFI at runtime or could they be statically set in a platform's DTB? How would other OS's get this information? Is this really linux specific? Rob
+ +It also depends on early_memremap() to parse the UEFI configuration tables. + +For actually enabling [U]EFI support, enable: +- CONFIG_EFI=y +- CONFIG_EFI_VARS=y or m + +After the kernel has mapped the required regions into its address space, +a SetVirtualAddressMap() call is made into UEFI in order to update +relocations. This call must be performed with all the code in a 1:1 +mapping. This implementation achieves this by temporarily disabling the +MMU for the duration of this call. This can only be done safely: +- before secondary CPUs are brought online. +- after early_initcalls have completed, since it uses setup_mm_for_reboot(). + +For verbose debug messages, specify 'uefi_debug' on the kernel command +line.