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diff --git a/documentation/AMD-S3.txt b/documentation/AMD-S3.txt new file mode 100644 index 0000000000..1ef87c0358 --- /dev/null +++ b/documentation/AMD-S3.txt @@ -0,0 +1,128 @@ + _____ ____ _____ ______ ____ ____ ____ _______ + / ____/ __ \| __ \| ____| _ \ / __ \ / __ \__ __| + | | | | | | |__) | |__ | |_) | | | | | | | | | + | | | | | | _ /| __| | _ <| | | | | | | | | + | |___| |__| | | \ \| |____| |_) | |__| | |__| | | | + \_____\____/|_| \_\______|____/ \____/ \____/ |_| + + __ __ _____ _____ ____ + /\ | \/ | __ \ / ____| |___ \ + / \ | \ / | | | | | (___ __) | + / /\ \ | |\/| | | | | \___ \ |__ < + / ____ \| | | | |__| | ____) | ___) | + /_/ \_\_| |_|_____/ |_____/ |____/ + + + S3 in Coreboot (V 1.1) +---------------------------------------- + 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 set the SLP_EN bit (See ACPI +registers). 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 resumes, 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 not 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. + +ACPI registers +============== +ACPI specification defines a group of registers. OSes handle all these +registers to read and write status to all the platform. +On AMD platform, these registers are provided by southbridge. For +example, Hudson uses PMIO 60:6F to define ACPI registers. +OSes don't have any specific driver to know where these registers +are. BIOS has the responsibility to allocated the IO resources and +write all these address to FADT, a ACPI defined table. + +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. + +Lifecycle of booting, sleeping and waking Coreboot and Ubuntu +============================================================= +1. Cold boot. +For a system with S3 feature, the BIOS needs to save some data to +non-volitile storage at cold boot stage. What data need to be save are +provided by AmdS3Save. After the wrapper calls the AmdS3Save, it gets +the VolatileStorage and NvStorage, which are where the data are +located. It is the wrappers's responsibility to save the data.[3][4] +Currently, the wrappers allocate a CBFS modules in BIOS image. Todo +that, the wrapper needs to have the ability to write flash chips. It +is not as comprehensive as flashrom. But for the SST chip on Parmer, +MX chip on Thather, coreboot works well.[5] + +2. OS goes in S3. + +3. BIOS detect S3 wakeup + +4. OS resumes. + + +Reference +========= +[1] ACPI40a, http://www.acpi.info/spec40a.htm +[2] Coreboot Vendorcode, {top}/src/vendorcode/amd/agesa/{family}/Proc/Common/ +[3] Coreboot AGESA wrapper, {top}/src/mainboard/amd/parmer/agesawrapper.c +[4] Coreboot AGESA wrapper, {top}/src/cpu/amd/agesa/s3_resume.c +[5] Coreboot Southbridge, {top}/src/southbridge/amd/agesa/hudson/spi.c |