lkml.org 
[lkml]   [2013]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 1/3] Documentation: arm: add UEFI support documentation
Adding devicetree list since you are defining bindings...

On 10/03/2013 06:24 AM, Leif Lindholm wrote:
> This patch provides documentation of the [U]EFI runtime services and
> configuration features.
>
> Cc: linux-doc@vger.kernel.org
> Signed-off-by: Leif Lindholm <leif.lindholm@linaro.org>
> Acked-by: Rob Landley <rob@landley.net>
> ---
> 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:

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.
>



\
 
 \ /
  Last update: 2013-10-03 20:41    [W:0.122 / U:1.484 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site