Hi Peter,
On Mon, 6 Jul 2020 at 05:52, Peter Geis pgwipeout@gmail.com wrote:
On Sun, Jul 5, 2020 at 11:35 AM Simon Glass sjg@chromium.org wrote:
Hi Peter,
On Sun, 5 Jul 2020 at 05:33, Peter Geis pgwipeout@gmail.com wrote:
On Sat, Jul 4, 2020 at 3:53 PM Simon Glass sjg@chromium.org wrote:
Hi Peter,
On Fri, 3 Jul 2020 at 06:33, Peter Geis pgwipeout@gmail.com 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'm building the cardhu board with tweaks for Ouya's specifications similar to my work for the linux kernel. I build the image using mkbootimg --kernel u-boot.bin --ramdisk /dev/null --output u-boot-android.bin. I then fastboot boot u-boot-android.bin.
I've tried tweaking the text base and tried both standard debug and low level debug.
Do you think you could give me some insight into where I'm going wrong?
Is it possible that fastboot expects a relocatable image? If you set up the debug UART very early you might be able to output a character in start.S ?
Yes, fastboot expects a relocatable image. As I understand it though, if I get the text base correct, U-boot will not need to relocate.
The debug UART is already set up when it fastboot jumps to the loaded kernel, So I should be able to dump data to the expected raw address and it will show up?
Yes, so long as you know the address. Is the MMU turned off? Cache?
It is unknown what state either of these are in, since I am unfamiliar at all with how fastboot functions with these. In U-boot yes the MMU was enabled as well as both I and D cache.
BTW does U-Boot have support for the fastboot protocol? Perhaps you could just use U-Boot?
The Ouya is locked with a signed boot loader, like most consumer android devices. Unlike most other devices, it does not have a hardware method for entering the bootloader in case of a brick. We are currently using a hacked kernel that stores another kernel in "safe" ram via kexec and hard resets the board, but a proper bootloader would be much more preferable.
OK. Maybe there is someone on this list with a bit more Android booting experienec?
I found one example of where fastboot chainloaded u-boot successfully on the galaxy nexus, from 2013. https://forum.xda-developers.com/galaxy-nexus/bootloader-boot-multi-boot-sup...
OK, I'm sure it is possible. Do you have the source code for the fastboot code that boots U-Boot?
No, we have the reference code here: https://android.googlesource.com/platform/bootable/bootloader/legacy/+/b1fde...
Unfortunately the behavior observed in the Ouya shows it has been heavily modified from this baseline.
I've reached out to the dev who performed the work on u-boot for insight as well.
If you have a kernel that loads at the same address that works, and it can display a UART character very early, then you should be able to make a U-Boot that does the same in the first few instructions. If you can't get that far, something else is going on. Do you have JTAG access?
Regards, Simon