This patch provides documentation of the [U]EFI runtime services and configuration features. Signed-off-by: Leif Lindholm <leif.lindholm@xxxxxxxxxx> --- Documentation/arm/00-INDEX | 3 +++ Documentation/arm/uefi.txt | 39 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 42 insertions(+) create mode 100644 Documentation/arm/uefi.txt diff --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 documentation diff --git a/Documentation/arm/uefi.txt b/Documentation/arm/uefi.txt new file mode 100644 index 0000000..5c48271 --- /dev/null +++ b/Documentation/arm/uefi.txt @@ -0,0 +1,39 @@ +The nomenclature EFI and UEFI are used interchangeably in this document. + +The implementation depends on receiving pointers to the UEFI memory map +and System Table in a Flattened Device Tree - so is only available with +CONFIG_OF. + +It (early) parses the FDT for the following parameters: +- 'efi-system-table': + Physical address of the system table. (required) +- 'efi-runtime-mmap': + Physical address of an EFI memory map, containing at least + the regions to be preserved. (required) +- 'efi-runtime-mmap-size': + Size in bytes of the provided memory map. (required) +- 'efi-mmap-desc-size': + Size of each descriptor in the memory map. (override default) +- 'efi-mmap-desc-ver': + Memory descriptor format version. (override default) + +Since UEFI firmware on ARM systems are required to use a 1:1 memory map +even on LPAE-capable systems, the above fields are 32-bit regardless. + +It also depends on early_ioremap to parse the memory map and preserve +the regions required for runtime services. + +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, sinze it uses setup_mm_for_reboot(). + +For verbose debug messages, specify 'uefi_debug' on the kernel command +line. -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
