Hi Leif, On Thu, Oct 03, 2013 at 12:24:39PM +0100, Leif Lindholm wrote: > This patch provides documentation of the [U]EFI runtime services and > configuration features. > > Cc: linux-doc@xxxxxxxxxxxxxxx > Signed-off-by: Leif Lindholm <leif.lindholm@xxxxxxxxxx> > Acked-by: Rob Landley <rob@xxxxxxxxxxx> > --- > Documentation/arm/00-INDEX | 3 +++ > Documentation/arm/uefi.txt | 47 ++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 50 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..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: > +- 'linux,efi-system-table': > + Physical address of the system table. (required) > + 64-bit value since an ARMv7 plattform may support LPAE, and to facilitate s/plattform/platform/ > + code sharing with arm64. Top 32 bits will be ignored, since UEFI specification > + mandates a 1:1 mapping of all RAM. You could use something like #size-cells to describe how big this is going to be. Is this Linux-specific -- it looks like something provided by EFI rather than the kernel itself. > +- '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. > + 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(). This is a little scary. If the format is so complicated, should it really be embedded? How big is this likely to be? Given that this is in a format defined externally, this isn't really Linux-specific. Maybe we need an "efi" pseudo-vendor prefix. > +- 'linux,efi-mmap-desc-size': > + Size of each descriptor in the memory map. (override default) What units is this in? How many u32 cells does this take up (one presumably)? > +- 'linux,efi-mmap-desc-ver': > + Memory descriptor format version. (override default) Type, format, valid values and their meaning? Thanks, Mark. > + > +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. > -- > 1.7.10.4 > > `> _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > -- 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
