Zheng Bao (zheng.bao@amd.com) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/1400
-gerrit
commit 7930ea30fbd307013159deeb1aeee0ca80d05736 Author: zbao fishbaozi@gmail.com Date: Fri Aug 3 13:53:10 2012 +0800
AMD S3: Add a document about S3 on AMD platform
See the document. Need review. Everything should be in Authentic English.
Change-Id: Idc528b8c6b0d5afe08fc4f4387b7bff30698f677 Signed-off-by: Zheng Bao zheng.bao@amd.com Signed-off-by: zbao fishbaozi@gmail.com --- documentation/AMD-S3.txt | 95 ++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 95 insertions(+), 0 deletions(-)
diff --git a/documentation/AMD-S3.txt b/documentation/AMD-S3.txt new file mode 100644 index 0000000..58ee0d7 --- /dev/null +++ b/documentation/AMD-S3.txt @@ -0,0 +1,95 @@ + _____ ____ _____ ______ ____ ____ ____ _______ + / ____/ __ | __ | ____| _ \ / __ \ / __ __ __| + | | | | | | |__) | |__ | |_) | | | | | | | | | + | | | | | | _ /| __| | _ <| | | | | | | | | + | |___| |__| | | \ | |____| |_) | |__| | |__| | | | + _________/|_| _______|____/ ____/ ____/ |_| + + __ __ _____ _____ ____ + /\ | / | __ \ / ____| |___ \ + / \ | \ / | | | | | (___ __) | + / /\ \ | |/| | | | | ___ \ |__ < + / ____ | | | | |__| | ____) | ___) | + /_/ __| |_|_____/ |_____/ |____/ + + + S3 in Coreboot +---------------------------------------- + Zheng Bao + zheng.bao@amd.com + fishbaozi@gmail.com + +Introduction +============ +This document is about how the feature S3 is implemented on coreboot, +specificly on AMD platform. This topic deals with ACPI spec, hardware, +BIOS, OS. We try to help coreboot users to realize their own S3. + +S3 in a nutshell +================ +The S3 sleeping state is a low wake latency sleeping state where all +system context is lost except system memory. [1]. S3 is a ACPI +definition. +To enter S3, write 3 in SLP_TYPx and setting the SLP_EN bit. But if +you do that, board can not resume at where it sleeps, because you +don't save the context. More often than not, we make the board go into +S3 by the tools which OSes provide. For windows, click +Start->sleep. For linux, some distribution provide a tools called +pm-suspend, which can make the system goto S3. If pm-suspend is not +available, we can run "echo mem > /sys/power/state", but this way may +not save all the needed context. +In S3 state, the power is off. So when the power button is pressed, +BIOS runs as it does in cold boot. If BIOS didn't detect whether +board boots or resume, it would go the same way as boot. It is not +what we expect. BIOS detects the SLP_TYPx. If it is 3, it means BIOS +are waking up. +BIOS is responsible for restore the machine state as it is before +sleep. It needs restore the memory controller, not overwriting memory +which is marked as reserved. For the peripheral which loses its +registers, BIOS needs to write the original value. +When everything is done, BIOS needs to find out the wakeup vector +provided by OSes and jump there. OSes also have work to do. We can go +to linux kernel or some other open source projects to find out how they +handle S3 resume. + +Memory Layout +============= +Restoring memory is the most important job done by BIOS. When the +power is off, the memory is maintained by standby power. BIOS need to +make sure that when flow goes to OS, everything in memory should be +the same as it was. + +The chip vendor will provide a way, or code, to wake up the memory +from sleeping. In AGESA 2008 arch, it is called AmdInitResume. + +The BIOS itself needs some memory to run. Either, BIOS marks the erea +as reserved in e820, or BIOS saves the content into reserved space. + +Here is the address Map for S3 Resume. Assumingly the total memory is 1GB. +00000000 --- 00100000 BIOS Reserved area. +00100000 --- 00200000 Free +00200000 --- 01000000 Coreboot ramstage area. +01000000 --- 2e160000 Free +2e160000 --- 2e170000 ACPI table +2e170000 --- 2ef70000 OSRAM +2ef70000 --- 2efe0000 Stack in highmem +2efe0000 --- 2f000000 heap in highmem +2f000000 TOM + +AMD requirements in S3 +====================== +Chip vendor like AMD will provide bunch of routines to restore the +board.[2] + * AmdS3Save: It is called in cold boot, save required register into + non-volatile storage. Currently, we use SPI flash to store the data. + * AmdInitResume: Restore the memory controller. + * AmdS3LateRestore: Called after AmdInitResume, restore other + register that memory. + * (SouthBridge)InitS3EarlyRestore, (SouthBridge)InitS3LateRestore: + Provided by Southbridge vendor code. Early is called before PCI + enumeration, and Late is called after that. + +Reference +========= +[1] ACPI40 +[2] Coreboot Vendorcode