On Mon, Jul 6, 2020 at 1:04 PM Stephen Warren swarren@wwwdotorg.org wrote:
On 7/3/20 6:32 AM, Peter Geis wrote:
Good Morning,
I am attempting to expand on the work for chainloading U-Boot on the nyan-big in order to chainload U-Boot on the Ouya Tegra30 device from fastboot. I have so far been unsuccessful at getting any output from U-Boot through this method.
I assume that fastboot executes the loaded code on the main CPU not on the boot CPU (AVP). U-Boot SPL on Tegra30 expects to start running on the AVP though; you would have to disable SPL to make this all work, and perhaps fix U-Boot to work without SPL present. I'm not sure what, if any, changes would be required to support that.
For background, see: https://http.download.nvidia.com/tegra-public-appnotes/index.html
Apologies for the resend, I realized I didn't reply to the list.
I admit I'm still extremely new to U-Boot, but this is the way I understand the boot flow. ROM does extremely low level init, then loads U-boot SPL. U-Boot SPL does basic init, ram, cpu and required peripherals, then loads U-Boot.bin. U-Boot.bin is U-Boot proper, with the full interface.
By loading U-Boot.bin as the nyan instructions indicated, I'm bypassing the SPL code as if it was already complete. The issue I have is I'm not sure what modifications were done to the T124 code to allow nyan to do this. I've compared the nyan configs to the cardhu configs and I don't see anything that sticks out to me. I've also dug through the nyan git log and I don't see anything that was specifically changed to allow chainloading on T124.
I also am unsure of where fastboot is loading the kernel in order to set the text base correctly.