[U-Boot] [RFC PATCH 0/1] SPL JTAG boot mode

[Sören Brinkmann]

On Mon, 2014-08-11 at 09:17AM -0400, Tom Rini wrote:
> On Mon, Aug 11, 2014 at 03:03:35PM +0200, Michal Simek wrote:
> 
> > Hi,
> > 
> > I have got this patch some time ago but I am not still
> > 100% sure about use case. Anyway Soren uses this mode
> > that's why let me send this patch and we can discuss
> > if this can be useful for someone else too.
> > 
> > The use case is to load U-Boot SPL to do init HW
> > and then load images via JTAG because RAM is initialized
> > and then run full u-boot.
> > There is an option to do HW initialization without
> > U-Boot SPL but there are some differences and it is just
> > better to directly use code which will run on the board
> > when everything is tested.
> 
> So in this case, you attach JTAG to the board, halt on reset, reset the
> board.  JTAG load in SPL and fiddle memory so that BOOT_DEVICE_JTAG is
> set, let SPL run, halt when you see the print (or set a breakpoint for
> that part, either way), then load U-Boot via JTAG, resume over the while
> loop, and then debug U-Boot as needed?

That is pretty much the flow correct. But I do not use it to debug
U-Boot, but boot our boards in our boardfarm. The flow is

1. Connect JTAG debugger
2. Download and run SPL
3. Stop execution when the SPL is done (and did initialize the DDR)
4. Load U-Boot and run U-Boot through JTAG
5. boot full OS etc.

I.e. the JTAG boot flow is used in automation quite a lot here.

	Thanks,
	Sören