* Keerthy <j-keerthy@xxxxxx> [190402 21:57]: > RTC plus DDR in self-refresh is a power saving mode where in the entire > system including the different voltage rails from PMIC are shutdown except > the ones feeding on to RTC and DDR. DDR is kept in self-refresh hence the > contents are preserved. > > RTC ALARM2 is connected to PMIC_EN line. TPS65218 PMIC has granular voltage rail > control. The voltage rail feeding RTC is kept on while the rest of the PMIC > regulators are powered off. > > Once the ALARM2 is triggered we enter the mode with DDR in self-refresh > and RTC Ticking. After a predetermined time an RTC ALARM1 triggers > waking up the system. The control goes to bootloader. The bootloader then checks > RTC scratchpad registers to confirm it was an rtc_only wakeup and follows > a different path, configure bare minimal clocks for ddr and then jumps to > the resume address in another RTC scratchpad registers and transfers the > control to Kernel. Kernel then restores the saved context. > > The patch series adds rtc-only + DDR mode support am am437x > Tested DS0, rtc+ddr back and forth on am437x-gp-evm board. > > This mode works only with u-boot built with am43xx_evm_rtconly_defconfig > > Additional patch is needed for omap-gpio save restore which will > come as fixes later. > > Hardware Description of this mode can be found here: > > http://www.ti.com/lit/ug/spruhl7h/spruhl7h.pdf Page 2884. > > Changes in v3: > > * Exported out omap_rtc_poweroff_program function & removed > the patch to add a generic rtc interface as it is specific > to am43 at the moment. Thanks I'll be applying this series into omap-for-v5.2/am4-pm today. Regards, Tony
