Thanks, Robert!
However, those "loads" just copy kernel/dtb into RAM for subsequent use,
they are not going to change the CPU configuration at u-boot level. They
cannot turn on the USB power until the control is passed to the kernel.
That way works: I load kernel and dtbs from eMMC, but tell them
"root=/dev/sda1 rootwait" (i.e. USB drive), so the kernel enables the USB
power, then mount the USB stick. With this approach you cannot load a
kernel *from* USB drive.
On Saturday, July 1, 2017 at 8:50:01 AM UTC-6, RobertCNelson wrote:
>
> On Fri, Jun 30, 2017 at 11:04 PM, Sergey Manucharian <s...@ara-ler.com
> <javascript:>> wrote:
> > Oh, thanks, William, I was inspired doing this by your post!
> >
> > The problem is that "usb start" starts u-boot's USB subsystem, it
> (probably)
> > has nothing to do with the CPU.
> > You explicitly mentioned that used a USB HDD with external power supply,
> but
> > I'm trying to boot off a USB flash drive. The CPU doesn't provide USB
> power
> > at early stage. If I provide power from an external source, everything
> works
> > fine.
> >
> > The latest u-boot supports loading overlays, I'm not sure whether it's
> > possible to load an overlays with the correct configuration of that pin
> and
> > then load kernel and stuff from USB flash drive.
>
> Why not?
>
> zImage:
>
> "loadimage=load ${devtype} ${bootpart} ${loadaddr}
> ${bootdir}/${bootfile}\0" \
>
>
> https://github.com/eewiki/u-boot-patches/blob/master/v2017.07-rc2/0001-am335x_evm-uEnv.txt-bootz-n-fixes.patch#L507
>
>
> overlay:
>
> "load ${devtype} ${bootpart} ${rdaddr} ${uboot_overlay}; " \
>
>
> https://github.com/eewiki/u-boot-patches/blob/master/v2017.07-rc2/0002-U-Boot-BeagleBone-Cape-Manager.patch#L800
>
>
> both use the devtype & bootpart references.. Thus if the kernel/dtb
> are on the same partition of the usb flash drive as the overlays,
> everything just works..
>
> But, you'll need to add the usb options here:
>
>
> https://github.com/eewiki/u-boot-patches/blob/master/v2017.07-rc2/0001-am335x_evm-uEnv.txt-bootz-n-fixes.patch#L277
>
>
> Regards,
>
> --
> Robert Nelson
> https://rcn-ee.com/
>
--
For more options, visit http://beagleboard.org/discuss
---
You received this message because you are subscribed to the Google Groups
"BeagleBoard" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to beagleboard+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/beagleboard/8fe903c1-9d73-42b5-888a-9b49653aaa56%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
