[sorry, failed with the header sending, trying it again]
Hi,
The following patches are needed before kernel can enter core retention. Namely, u-boot is enabling some functionality too early in the init phase which seems not to be needed, and it is causing trouble later on. I haven't found any other workaround for any of the following issues than to patch the bootloader. I even tried resetting each IP module to no avail.
UART2 is used to communicate with the wifi chip, and muxing the pads too early for UART2 usage hangs the UART module, preventing idle.
DSP/IVAHD/cortex-m3 cores don't have any firmware to execute, so taking them out of reset is generally a bad idea. Also, all cores will prevent any idle later on if taken out of reset.
FSUSB module has similar issue as UART2, if it is enabled during boot, it will never go to idle anymore.
Tested with omap4 panda es board.
If someone is interested in testing the kernel I have used, it can be found here:
git://gitorious.org/~kristo/omap-pm/omap-pm-work.git branch: mainline-3.4-omap4-dev-off
Use omap2plus_defconfig, boot it up to shell and do "echo mem > /sys/power/state".
-Tero