Revision bd8733738c5af6114dd15d340b3f8713e9b624c2 authored by Boris Brezillon on 08 February 2015, 18:23:42 UTC, committed by Linus Walleij on 18 March 2015, 01:01:36 UTC
The gpiochip_lock_as_irq call can fail and return an error, while the irq_startup is not expected to fail (returns an unsigned int which is not checked by irq core code). irq_request/release_resources functions have been created to address this problem. Move gpiochip_lock/unlock_as_irq calls into irq_request/release_resources functions to prevent using a gpio as an irq if the gpiochip_lock_as_irq call failed. Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com> Acked-by: Ludovic Desroches <ludovic.desroches@atmel.com> Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com> Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
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uefi.txt
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.
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