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x86: Document ACPI S3 support

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Now that we have ACPI S3 support on Intel MinnowMax board, document
some generic information of S3 and how to test it.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Stefan Roese <sr@denx.de>
This commit is contained in:
Bin Meng 2017-04-21 07:24:49 -07:00
parent 4f93c29b54
commit 13c9d84825
1 changed files with 18 additions and 6 deletions
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doc/README.x86
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@ -1014,12 +1014,12 @@ compile ACPI DSDT table written in ASL format to AML format. You can get
the compiler via "apt-get install iasl" if you are on Ubuntu or download
the source from [17] to compile one by yourself.
Current ACPI support in U-Boot is not complete. More features will be added
in the future. The status as of today is:
Current ACPI support in U-Boot is basically complete. More optional features
can be added in the future. The status as of today is:
* Support generating RSDT, XSDT, FACS, FADT, MADT, MCFG tables.
* Support one static DSDT table only, compiled by Intel ACPI compiler.
* Support S0/S5, reboot and shutdown from OS.
* Support S0/S3/S4/S5, reboot and shutdown from OS.
* Support booting a pre-installed Ubuntu distribution via 'zboot' command.
* Support installing and booting Ubuntu 14.04 (or above) from U-Boot with
the help of SeaBIOS using legacy interface (non-UEFI mode).
@ -1027,9 +1027,6 @@ in the future. The status as of today is:
of SeaBIOS using legacy interface (non-UEFI mode).
* Support ACPI interrupts with SCI only.
Features not supported so far (to make it a complete ACPI solution):
* S3 (Suspend to RAM), S4 (Suspend to Disk).
Features that are optional:
* Dynamic AML bytecodes insertion at run-time. We may need this to support
SSDT table generation and DSDT fix up.
@ -1046,6 +1043,21 @@ command from the OS.
For other platform boards, ACPI support status can be checked by examining their
board defconfig files to see if CONFIG_GENERATE_ACPI_TABLE is set to y.
The S3 sleeping state is a low wake latency sleeping state defined by ACPI
spec where all system context is lost except system memory. To test S3 resume
with a Linux kernel, simply run "echo mem > /sys/power/state" and kernel will
put the board to S3 state where the power is off. So when the power button is
pressed again, U-Boot runs as it does in cold boot and detects the sleeping
state via ACPI register to see if it is S3, if yes it means we are waking up.
U-Boot is responsible for restoring the machine state as it is before sleep.
When everything is done, U-Boot finds out the wakeup vector provided by OSes
and jump there. To determine whether ACPI S3 resume is supported, check to
see if CONFIG_HAVE_ACPI_RESUME is set for that specific board.
Note for testing S3 resume with Windows, correct graphics driver must be
installed for your platform, otherwise you won't find "Sleep" option in
the "Power" submenu from the Windows start menu.
EFI Support
-----------
U-Boot supports booting as a 32-bit or 64-bit EFI payload, e.g. with UEFI.