Am Dienstag, 19. September 2017, 11:10:29 CEST schrieb Dr. Philipp Tomsich:
Andy,
On 19 Sep 2017, at 09:19, Andy Yan andy.yan@rock-chips.com wrote:
Hi Philipp:
On 2017年09月19日 10:06, Andy Yan wrote:
Hi Philipp:
On 2017年09月19日 02:18, Philipp Tomsich wrote:
Recent discussions confirmed (what the code always assumed): the Rockchip BROM always enters U-Boot with the stack-pointer valid (i.e. the U-Boot startup code is running off the BROM stack).
We can thus replace the back-to-bootrom code (i.e. both the save_boot_params and back_to_bootrom implementations) using C-code based on setjmp/longjmp. The new implementation is already structured to allow an easy drop-in of Andy's changes to enter download-mode when returning to the BROM.
This entails one minor tweak to asm/system.h, which only exported the save_boot_params_ret prototype for ARMv7, but not for AArch64.
For v2, we force bootrom.o to alway be emitted as A32 (not T32), so we can safely call save_boot_params_ret().
This still have a problem, because the setjmp implementation for ARM32 platform has humb code when CONFIG_SYS_THUMB_BUILD is>> enabled, this is a default setting for most ARMv7 boards. #if CONFIG_IS_ENABLED(SYS_THUMB_BUILD) ".align 2\n" "adr r0, jmp_target\n" "add r0, r0, $1\n" // r0 stored the jump target address and with bit[0] = 1, this will trigger a thumb switch in longjmp with code "bx r0" #endif
When I force the setjmp code go arm code path, I can back to bootrom successfully, But I got a data abort exception in later. it seems it happens when bootrom finished the uboot code copy, when jump to sdram, I need a further debug.
I found that r9 also need to be preserved, it seems that it hold the sdram base.
Thanks for testing and debugging: this is invaluable support, as I only have AArch64 boards to test.
The r9 issue will be easy enough to resolve. However, it looks like I will need more work on setjmp/longjmp to make this safe both for T32 and A32. Plus: I need to figure out why this didn’t show in my disassembly (I don’t remember whether it was a rk3188 or rk3288 board I looked at).
Might be tomorrow or Thursday until I can provide an new version.
From this conversation, it looks to me that I should wait for that new version for testing on rk3188, as it will likely show the same issues, right?
Heiko