Hi,
We have a custom DM37x based board with two USB interfaces MUSB OTG and EHCI. We have implemented suspend state within the BSP and in that state following is implementated for the two USB interfaces.
EHCI:
EHCI controller of DM37x is connected to external PHY. Suspend state is entered by enabling SUSPEND bit in the EHCI controller. The external PHY device controls 5V USB power supply through CPEN bit in the PHY register set. We have observed that 5V supply disappears when system enters suspend state. I would like to do further power optimization by switching OFF the power supply for the external PHY device. Few queries in this regard,
- Is this Technically feasible and has anyone tried this option?
- If yes has any issue being observed on EHCI port after waking up from Suspend state?
- Any key points to be taken care in wake up code for EHCI controller?
USB OTG:
OTG controller of DM37x is connected to external PHY using TPS65950 OTG PHY (similar to one on OMAP3 EVM). Suspend state is entered by enabling SUSPEND bit in the PHY. However we have not currently disabled 5V OTG supply coming out from PHY. We would like to implement the same.
- Is this Technically feasible and has anyone tried this option?
- If yes has any issue being observed on OTG port after resuming from Suspend state?
- Any key points to be taken care in wake up code for OTG controller and PHY?
An valuable inputs from you in this regard will be really helpful for us.
Regards,
~Ajit