Kernel stores information to the RTC_SCRATCH0 and RTC_SCRATCH1 registers for wakeup from RTC-only mode. Parse these registers during SPL boot and jump to the kernel resume vector if the device is waking up from RTC-only mode.
The RTC scratch register layout used is:
SCRATCH0 : bits00-31 : kernel resume address SCRATCH1 : bits00-15 : RTC magic value used to detect valid config SCRATCH1 : bits16-31 : board type information populated by bootloader
During the normal boot path the SCRATCH1 : bits16-31 are updated with the eeprom read board type data. In the rtc_only boot path the rtc scratchpad register is read and the board type is determined and correspondingly ddr dpll parameters are set. This is done so as to avoid costly i2c read to eeprom.
RTC-only mode support is currently only enabled for am43xx_evm_rtconly_config. This is not to be used with epos evm builds.
Dave Gerlach (1): am43xx: Do not allow EMIF to control DDR_RESET in rtconly config
Tero Kristo (1): ARM: AM43xx: Add support for RTC only mode
arch/arm/include/asm/arch-am33xx/clock.h | 6 ++ arch/arm/mach-omap2/am33xx/Kconfig | 14 ++++ arch/arm/mach-omap2/am33xx/board.c | 110 +++++++++++++++++++++++++++--- arch/arm/mach-omap2/am33xx/clock.c | 10 +++ arch/arm/mach-omap2/am33xx/clock_am43xx.c | 21 ++++++ arch/arm/mach-omap2/am33xx/emif4.c | 5 ++ board/ti/am43xx/MAINTAINERS | 1 + board/ti/am43xx/board.c | 56 +++++++++++++++ configs/am43xx_evm_rtconly_defconfig | 59 ++++++++++++++++ 9 files changed, 274 insertions(+), 8 deletions(-) create mode 100644 configs/am43xx_evm_rtconly_defconfig