Delay recognizing USB-Drive with Kernel 5.9.12

[Neil Armstrong]

Hi,

On 15/01/2021 15:27, thilo wrote:
> Hello!
> I am new to linux, please excuse false statements :-)).
> I think there is a USB_PWR_EN-problem in the kernel (UAS-driver???)
> NO            delay recognizing USB-drive with kernel 4.9.247
>>20 sec    delay recognizing USB-drive with kernel 5.9.12
> 
> Installed Armbian on SD on an Odroid n2+.
> Wanted to move system to USB-SSD, used nand-sata-install.
> After that, didn't boot.
> New install on SD.
> Realized that most of the time it took >20 sec to recognize USB-SSD.
> I felt, failing boot was due to slow USB-drive recognition (system drive
> not available at boot).
> 
> in kern.log:
> ... localhost kernel: [   33.760038] USB_PWR_EN: disabling
> ...
> ... localhost kernel: [  587.836268] usb 1-1.3: new full-speed USB
> device number 6 using xhci-hcd
> 
> Did some research, found:
> https://forum.armbian.com/topic/13580-odroid-n2-kernel49-no-boot-on-usb-sata-ssd/
> with:
> 'BTW what is USB_PWR_EN, are we looking at something interesting here?'

USB_PWR_EN is the regulator that powers the micro USB OTG port, when nothing
is connected or a is connected to a PC, power is disabled.
Connecting a device via a microUSB-to-USB-A cable will enable this regulator.

> and a link to:
> https://forum.armbian.com/topic/11741-boot-from-ssd-with-n2/page/3/
> with:
> 'None ... delay was necessary when using kernel 4.9.x so ... seems ...
> problem with the 5.x kernel series, presumably around the UAS driver ...'
> 
> With Armbian-config, changed
> Kernel 5.9.12 to 4.9.247 (gladly very easy with that!)
> After that recognition of USB-SSD was fast.
> Another nand-sata-install.
> New boot, worked: root part is on USB-SSD!!!
> 
> So: problem with 5.x kernel, see top of mail.
> 
> Would be glad to get feedback.

As Martin says, the Amlogic kernel contains a lot a tweaks which are not present
on the mainlinx Linue tree, maybe if you identify what delays this detection we may
find how to reduce such delays on Amlogic SoCs.


Neil

> 
> Thilo
> 
> 
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