i.MX8/i.MX8X: usbotg3: e_gadget low bit rate enabling CONFIG_ARM_SMMU

[oferausterlitz]

Hi NXP Team

I noticed low bit rate (~10 Mbits/sec ) using iperf3 test on gadget ethernet. To get expected bit rate at ~350Mbits/sec the “CONFIG_ARM_SMMU=y” present in the NXP defconfig has to be removed but I don't know the consequences even though I didn't notice any problems after the removal. I verified that the low performance is related to only e_gadget while pen drive connected to usbotgt3 works fine. Can you suggest if I can remove CONFIG_ARM_SMMU or if it is better to leave the flag and accept the low bit rate on ethernet gadget?

Thanks

Ofer

[Zhiming_Liu]

There is no SMMU channel for usb, but removing SMMU would cause other performace issue.