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authorLinus Torvalds <torvalds@linux-foundation.org>2014-06-05 13:15:32 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-05 13:15:32 -0700
commitc3c55a07203947f72afa50a3218460b27307c47d (patch)
treede3a2f8adbb3bea4bba1df0f709b0d6c1f4e87b7 /Documentation/arm
parent046f153343e33dcad1be7f6249ea6ff1c6fd9b58 (diff)
parent74bcc2499291d38b6253f9dbd6af33a195222208 (diff)
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Merge branch 'arm64-efi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into next
Pull ARM64 EFI update from Peter Anvin: "By agreement with the ARM64 EFI maintainers, we have agreed to make -tip the upstream for all EFI patches. That is why this patchset comes from me :) This patchset enables EFI stub support for ARM64, like we already have on x86" * 'arm64-efi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: arm64: efi: only attempt efi map setup if booting via EFI efi/arm64: ignore dtb= when UEFI SecureBoot is enabled doc: arm64: add description of EFI stub support arm64: efi: add EFI stub doc: arm: add UEFI support documentation arm64: add EFI runtime services efi: Add shared FDT related functions for ARM/ARM64 arm64: Add function to create identity mappings efi: add helper function to get UEFI params from FDT doc: efi-stub.txt updates for ARM lib: add fdt_empty_tree.c
Diffstat (limited to 'Documentation/arm')
-rw-r--r--Documentation/arm/00-INDEX2
-rw-r--r--Documentation/arm/uefi.txt64
2 files changed, 66 insertions, 0 deletions
diff --git a/Documentation/arm/00-INDEX b/Documentation/arm/00-INDEX
index a94090cc785d..3b08bc2b04cf 100644
--- a/Documentation/arm/00-INDEX
+++ b/Documentation/arm/00-INDEX
@@ -46,5 +46,7 @@ swp_emulation
- SWP/SWPB emulation handler/logging description
tcm.txt
- ARM Tightly Coupled Memory
+uefi.txt
+ - [U]EFI configuration and runtime services documentation
vlocks.txt
- Voting locks, low-level mechanism relying on memory system atomic writes.
diff --git a/Documentation/arm/uefi.txt b/Documentation/arm/uefi.txt
new file mode 100644
index 000000000000..d60030a1b909
--- /dev/null
+++ b/Documentation/arm/uefi.txt
@@ -0,0 +1,64 @@
+UEFI, the Unified Extensible Firmware Interface, is a specification
+governing the behaviours of compatible firmware interfaces. It is
+maintained by the UEFI Forum - http://www.uefi.org/.
+
+UEFI is an evolution of its predecessor 'EFI', so the terms EFI and
+UEFI are used somewhat interchangeably in this document and associated
+source code. As a rule, anything new uses 'UEFI', whereas 'EFI' refers
+to legacy code or specifications.
+
+UEFI support in Linux
+=====================
+Booting on a platform with firmware compliant with the UEFI specification
+makes it possible for the kernel to support additional features:
+- UEFI Runtime Services
+- Retrieving various configuration information through the standardised
+ interface of UEFI configuration tables. (ACPI, SMBIOS, ...)
+
+For actually enabling [U]EFI support, enable:
+- CONFIG_EFI=y
+- CONFIG_EFI_VARS=y or m
+
+The implementation depends on receiving information about the UEFI environment
+in a Flattened Device Tree (FDT) - so is only available with CONFIG_OF.
+
+UEFI stub
+=========
+The "stub" is a feature that extends the Image/zImage into a valid UEFI
+PE/COFF executable, including a loader application that makes it possible to
+load the kernel directly from the UEFI shell, boot menu, or one of the
+lightweight bootloaders like Gummiboot or rEFInd.
+
+The kernel image built with stub support remains a valid kernel image for
+booting in non-UEFI environments.
+
+UEFI kernel support on ARM
+==========================
+UEFI kernel support on the ARM architectures (arm and arm64) is only available
+when boot is performed through the stub.
+
+When booting in UEFI mode, the stub deletes any memory nodes from a provided DT.
+Instead, the kernel reads the UEFI memory map.
+
+The stub populates the FDT /chosen node with (and the kernel scans for) the
+following parameters:
+________________________________________________________________________________
+Name | Size | Description
+================================================================================
+linux,uefi-system-table | 64-bit | Physical address of the UEFI System Table.
+--------------------------------------------------------------------------------
+linux,uefi-mmap-start | 64-bit | Physical address of the UEFI memory map,
+ | | populated by the UEFI GetMemoryMap() call.
+--------------------------------------------------------------------------------
+linux,uefi-mmap-size | 32-bit | Size in bytes of the UEFI memory map
+ | | pointed to in previous entry.
+--------------------------------------------------------------------------------
+linux,uefi-mmap-desc-size | 32-bit | Size in bytes of each entry in the UEFI
+ | | memory map.
+--------------------------------------------------------------------------------
+linux,uefi-mmap-desc-ver | 32-bit | Version of the mmap descriptor format.
+--------------------------------------------------------------------------------
+linux,uefi-stub-kern-ver | string | Copy of linux_banner from build.
+--------------------------------------------------------------------------------
+
+For verbose debug messages, specify 'uefi_debug' on the kernel command line.