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| author | Leif Lindholm <leif.lindholm@linaro.org> | 2013-07-16 23:07:19 +0100 |
|---|---|---|
| committer | Leif Lindholm <leif.lindholm@linaro.org> | 2013-08-09 17:58:30 +0100 |
| commit | b90b4872178d9ba32d867e2a4e16d6a83b79088b (patch) | |
| tree | cd68d804db5b2fc468ac003263ae533ed3fb0944 | |
| parent | ca039ab4c869b23ba380b5b9d0d9d83a065bd7e7 (diff) | |
Documentation: arm: add UEFI support documentation
Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
| -rw-r--r-- | Documentation/arm/00-INDEX | 3 | ||||
| -rw-r--r-- | Documentation/arm/uefi.txt | 39 |
2 files changed, 42 insertions, 0 deletions
diff --git a/Documentation/arm/00-INDEX b/Documentation/arm/00-INDEX index 4978456df1cc..87e01d145222 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 000000000000..5c482715a9dc --- /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. |