System clock becomes slow in custom board imx6ul

[pratyushtomar]

We have a custom board based on imx6ul evk except that we are using lpdd2 ram. The problem is that if we use ondemand or conservative mode the system clock becomes very slow. For every 10 seconds update the board system clock updates only 3 sec. But as soon as we change board mode to performance mode the system clock works fine. In evk we didn't observe any such behaviour if we use ondemand or conservative mode in evk. The system clock works fine in every mode. What can be the possible reason for this behaviour in our custom board?

[pratyushtomar]

we did further testing and found out that the issue is not due to PN7150. It's because of USB OTG controller module of cpu remains not powered if usb cable is unplugged. If we plugin the cable the clock works fine even if we are not using power from usb to run our board. Now the question is why is this happening?

[gusarambula]

Hello Pratyush Tomar,

Were you able to find the root cause of this behavior? Is the USB OTG circuity the same as in the i.MX6UL EVK? I would recommend reviewing the voltages on the processor without the USB OTG connected as perhaps it is somehow affecting the voltages the processor receives and thus affects the system clock.

Please let us know of your findings!

Regards,

[pratyushtomar]

Hello,

We still haven't been able to find root cause of this behavior. The USB OTG circuity is similar to one in i.MX6UL EVK. However we observed following thing, if we disable CONFIG_REGULATOR_GPIO in kernel config then we observe similar behavior of system clock slowing down in ondemand and conservative mode even in EVK board. And after enabling it  the system clock works fine in EVK in onedemand and conservative mode. But anyway CONFIG_REGULATOR_GPIO has no effect on our board the system clock always slows down.