I’m new to debugging USB power issues in the Kernel, so I am looking for help in
understanding the sequence of events / where to continue looking:
My board is loosely based on the mangOH green, it is using Legato for wp76xx R12,
Linux kernel 3.18.122.
My issue is that on powering up the board, 2 devices directly connected to the HSIC host,
are not enumerated. The 2 devices are Ethernet (on HSIC) and an SD card reader.
I have 2 boards: one which exhibits the issue and one that does not.
The only differences that I can see from dmesg/logread are:
swi-mdm9x28-wp user.info kernel: [ 1.141708] msm_hsic_host 7c00000.hsic_host: HSIC-USB in low power mode swi-mdm9x28-wp user.info kernel: [ 1.141916] msm_hsic_host 7c00000.hsic_host: HSIC-USB exited from low power mode . . swi-mdm9x28-wp user.err kernel: [ 6.530202] usb 1-1: device descriptor read/64, error -110
So with a bit of digging I see that msm_hsic_runtime_suspend() from ehci-msm-hsic.c is being called,
bu I know of no reason why msm_hsic_runtime_suspend(0 is getting called -
the USB controller or system should not be entering into suspend.
I suppose disabling USB sleep might help, but I still don’t understand why/how it’s being told to go to sleep.
Any pointers on where to look greatly received.