Porting barebox (devicetree) to Variscite iMX6 SOM

[Michael Burkey <mdburkey@gmail.com>]

Sascha,

Things are working fairly well at this point.

I can boot barebox on the Variscite SOM.
I can boot Linux from barebox out of either NAND or off the SD card.
I can update the kernel and/or rootfs to NAND or SD from barebox.
I can mount and access both the SD card and USB mass storage devices.

So, basically, it's usable at this point.

Which brings me to my next couple of issues...

The first involves mounting USB mass storage devices. When I do a
probe of the USB bus, it works fine as long as I have at least one low
speed USB device connected (mouse, keyboard, etc). If I do not have a
low speed USB device connected, it never probes anything beyond the
initial hub and my flash drive never gets detected.

The Variscite dev board has three USB ports, but all of which are
connected to a USB hub IC on the board, so none of them are tied
directly to the iMX6 itself (all go through the hub).

The output is as follows (with a flash drive connected, but nothing else):

USB: scanning bus for devices...
Bus 001 Device 002: ID 0424:2514
Bus 001 Device 001: ID 0000:0000 EHCI Host Controller
2 USB Device(s) found

and with a mouse and a flash drive connected:

USB: scanning bus for devices...
Using index 0 for the new disk
Bus 001 Device 004: ID 125f:c08a ADATA USB Flash Drive
Bus 001 Device 002: ID 0424:2514
Bus 001 Device 001: ID 0000:0000 EHCI Host Controller
4 USB Device(s) found

Any ideas on where to look in the code for this?
Have you seen this behavior before?
I don't think it is a DTS file problem (unless I'm missing something).


The second item, which is MUCH lower priority, would be getting the
onboard PHY working to make transferring files to/from the board a bit
easier in barebox.

The issues I'm running into:
1) the board uses a Micrel KSZ9031 Phy, which doesn't appear to be
supported. However, it is very close to the KSZ9021 and I *think* I
have changed the micrel_phy.c file to where it probably would work.

2) The other issue is that the reset procedure used in Variscite's BSP
version of u-Boot for this phy is a bit, well, odd. I'm not sure if it
is specifically necessary or not. Basically, they initially assign all
of the ports over to GPIO6 so that they can force all the phy lines to
high during the reset. Then, once the reset is finished, they change
the iomux settings back to the correct ones for ethernet operation. I
suspect this would probably require adding code directly to board.c
and removing the fec entries from the DTS file.

3) Similarly with item #2, the power supply for the phy appears to be
routed through the PF0100, but is NOT enabled with the chips default
values. Immediately after startup, they hand configure the voltage
rail to the phy via I2C commands directly to the PF0100. I have
already added this code to the board.c file for barebox and it appears
to work properly. Unfortunately, the devicetree probe of the fec
controller happens BEFORE this is done, which means that the phy isn't
powered during the probe operation. Additionally, trying to move it
over to lowlevel.c for early startup (like the UART) isn't a simple
option since the I2C drivers need to be started so I can access the
PF0100.

So, if you were doing this, which option would you probably choose
(assuming my logic is correct):
1) just leave the fec out of the devicetree and bring it up later in
the board file (i.e. old style).
2) leave the fec out of the devicetree, configure the PF0100, then
apply devicetree overlays to add in the fec and then reprobe the tree?

Once again, the ethernet is not a big deal for me since we aren't
actually using it ourselves. It is just a bit of a convenience item to
have (though I can always use a USB NIC).

Thanks again for all your help!
Michael Burkey

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