-----Original Message----- From: Michal Simek [mailto:michal.simek@xilinx.com] Sent: Monday, August 11, 2014 6:30 AM To: Tom Rini; Michal Simek Cc: u-boot@lists.denx.de; Stephen Warren; Ezra Savard; Soren Brinkmann; Roger Quadros Subject: Re: [U-Boot] [RFC PATCH 0/1] SPL JTAG boot mode
On 08/11/2014 03:17 PM, 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,
BOOT_DEVICE_JTAG for zynq case will be setup in spl_boot_device() based on dip-switch boot mode setup read from SLCR.
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?
In general that's my impression how Soren uses it. I would let him to confirm that this is his use case.
Not sure if he is just loading images when cpu is in while(1) loop and let u- boot spl continue. I can imagine that it will be just easier to let u-boot spl end up in while loop instead of trying to find out address for adding breakpoint.
In our use case, we do not have physical access to the board.
Previously, u-boot spl would hang when ready for the u-boot image; the explicit JTAG boot mode keeps from attempting to load images from RAM.
The while(1) loop is, as mentioned by Michal, just an easy, known place to let the u-boot spl end up before loading images.
Soren will be back in one week and it would be best for him to chime in.
Thanks, Ezra
I would let Soren or Ezra to justify this use case because I have doubts.
Thanks, Michal
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