Messages in this thread | | | Subject | Re: Embedded USB Debug(EUD) driver | From | Randy Dunlap <> | Date | Sat, 7 Aug 2021 07:54:57 -0700 |
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On 8/7/21 7:23 AM, Subhashini Rao Beerisetty wrote: > On Sat, Jul 31, 2021 at 11:12 AM Greg KH <gregkh@linuxfoundation.org> wrote: >> >> On Fri, Jul 30, 2021 at 11:33:09PM +0530, Subhashini Rao Beerisetty wrote: >>> Hi All, >>> >>> I'm currently looking for the Embedded USB Debug (EUD) interface driver. >> >> For what specific hardware? Do you have the needed "special" cable? We >> have support in the kernel for some types of these cables, what kernel >> versions have you tried that did not work for this?
> It's for MSM hardware and yes we have the "special" cable. > I could not find the device driver for this in the mainline tree. It > would be helpful if you could point me to the kernel tree which > supports this feature. We will compile this suggested kernel and > necessary drivers and then will give a try on our hardware
Hi, See USB_SERIAL_DEBUG in drivers/usb/serial/. That symbol builds usb_debug.c in that same directory.
It may help to read Documentation/x86/earlyprintk.rst.
My own cheat sheet (quick reference) says this: (it may or may not help you) (it might need some updating for XHCI): ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Using USB debug port (on a USB EHCI controller)
On the system under test:
CONFIG_USB_EHCI_HCD=y
kernel command line: earlyprintk=dbgpN,keep
With an XHCI controller, use: earlyprintk=xdbcN,keep
Also add: console=tty0 or console=ttyUSB0 for console output to go to the serial port.
Make sure that USB_SERIAL=y, USB_SERIAL_CONSOLE=y, and USB_SERIAL_DEBUG=y.
------ On the logging system: (requires CONFIG_USB_SERIAL_DEBUG=y)
Run minicom and tell it to connect to /dev/ttyUSB#. Optionally have it log all messages to a file.
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-- ~Randy
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