Remote Access to H/W

[Anand Gadiyar]

Dave Martin wrote:
> On Fri, Feb 25, 2011 at 10:58 AM, Loďc Minier
> <loic.minier at linaro.org> wrote:
> > On Thu, Feb 24, 2011, Mounir Bsaibes wrote:
> >> We have a need for a Panda and a Beagle to compare & fix performance.
> >> As I recall from last meeting, the Panda's USB I/O has 2x performance
> >> degradation from Beagle.
> >> Per or Mian may have more details on that.
> >
> >  Ok; interesting!
> >
> >  My initial fear was that the kernel testing might trigger unbootable
> >  boards and that it would be tricky to work with unstable kernels
> >  remotely; for USB performance testing, I can see that we could set it
> >  up for remote testing, but we need to have something plugged to USB
and
> >  be careful to use the same hardware on both boards so that it
compares
> >  usefully.
>
> If we never upgrade the bootloader, and make sure that the known-good
> bootscripts/images are never modified/removed, then we should
> generally be able to avoid bricking.
>
> On vexpress for example, we have a known-good U-Boot in flash which
> can be used to recover the board if needed.
>
> Where random hardware has to be plugged in, that could be a bit harder
> to arrange...

I work remotely with my Pandaboard - I have the UART plugged into
a desktop and a USB relay board for the power supply. I have
a screen session with picocom running on the desktop all the time.

I keep known-working loaders on the SD card with a "uImage-flasher"
image alongside. (Essentially a kernel with drivers enabled for the EHCI
controller and the USB-LAN chip + initramfs + tiny scripts that pick
up a kernel image from a hardcoded location using tftp and replace
the one currently on the SD card.

To get into the flasher image, I just halt manually in u-boot and
load uimage-flasher. Else, u-boot is configured to pick up 'uImage'
by default.

Issues:
- Can't work remotely if you're working on x-loader code (flashing
  a wrong image MLO/u-boot could mean a physical visit to the board)
--- Okay for u-boot if you want to load u-boot from within a known-
    working u-boot.
- Someone 'borrows' the board without asking.
--- I've had folks walk in, see the board apparently unused, and
  borrow it for a - leaving me wondering why the board stopped
  responding. :(

- Anand