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| -rw-r--r-- | doc/README.x86 | 24 |
1 files changed, 18 insertions, 6 deletions
diff --git a/doc/README.x86 b/doc/README.x86 index a38cc1b..c69dc1c 100644 --- a/doc/README.x86 +++ b/doc/README.x86 @@ -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. |