Linux/AM3352: USB Suspend before going to Standby mode

Angel Falcon

Part Number: AM3352

Tool/software: Linux

Hello,

We are using am3352 with linux kernel 4.4.19 from TI SDK.

We connect USB1 to a modem and in some sistuations we need to go to stand-by mode to save power. We see that USB is disconnected and connected again in this situation.

We would like to suspend USB before going to stand-by and resume it when running again, so we could avoid USB disconnection.

Could you please help us?

Best regards

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

The software team have been notified. They will respond here.

0 Bin Liu over 8 years ago

TI__Guru**** 176781 points

Angel,

Right now there is no perfect way in Linux to prevent usb device disconnect in system standby mode for AM335x. It is not related to USB suspend, but while the system enters standby mode, USB clock is gated and VBUS power is turned off. While the system is resuming from standby, the kernel USB stack disconnects and re-connects the USB devices. There might be a way to solve this, but I haven't got time to look at it yet.

Linux kernel has a function called USB Persist (see kernel doc www.kernel.org/.../persist.txt), which can prevent USB device got disconnected, but it doesn't work for some USB devices.

0 Angel Falcon over 8 years ago in reply to Bin Liu

Expert 1160 points

Hi,

Thanks a lot for your answer. I will test with USB persist to check if it fits our requirements.

Best regards

Angel

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Linux/AM3352: USB Suspend before going to Standby mode