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 turned out to require a some tweaking to system.h (making sure that the prototype for save_boot_params_ret is visible for A64)and start.S (so binutils knows that this is a possible function entry and it can correctly insert A32-to-Thumb transitions) and taking the axe to setjmp.h (which created quite a few issues with it not expecting A32/T32/Thumb call-sites and some fragility from GCC being smart about the clobber-list of the inline assembly... which led to r9 not being saved or restored).
Changes in v3: - tracked the root-cause why no interwork branch was emitted and fixed it using a '.type'-directive in start.S to mark save_boot_params_ret as a (possible) function-entry. - converted setjmp/longjmp from inline-assembly to separate .S files to improve predicatability if emitted code
Changes in v2: - [added in v2] chain back_to_bootrom calls for SPL, first returning to the TPL (using the same mechanism) and the to the BROM from the TPL - also covers the RK3188 (which I had originally missed)
Philipp Tomsich (6): arm: make save_boot_params_ret prototype visible for AArch64 arm: mark save_boot_params_ret as a function arm: provide a PCS-compliant setjmp implementation rockchip: back-to-bootrom: replace assembly-implementation with C-code rockchip: back-to-bootrom: rk3188: chain from SPL via TPL to the BROM rockchip: back-to-bootrom: allow passing a cmd to the bootrom
arch/arm/cpu/armv7/start.S | 1 + arch/arm/include/asm/arch-rockchip/bootrom.h | 30 ++++++--- arch/arm/include/asm/setjmp.h | 94 ++++------------------------ arch/arm/include/asm/system.h | 62 +++++++++--------- arch/arm/lib/Makefile | 6 ++ arch/arm/lib/setjmp.S | 37 +++++++++++ arch/arm/lib/setjmp_aarch64.S | 42 +++++++++++++ arch/arm/mach-rockchip/Makefile | 4 +- arch/arm/mach-rockchip/bootrom.c | 54 +++++++++++++++- arch/arm/mach-rockchip/rk3036-board-spl.c | 2 +- arch/arm/mach-rockchip/rk3188-board-spl.c | 14 +---- arch/arm/mach-rockchip/rk3188-board-tpl.c | 19 +++--- arch/arm/mach-rockchip/rk322x-board-spl.c | 2 +- arch/arm/mach-rockchip/rk3288-board-spl.c | 4 +- arch/arm/mach-rockchip/rk3368-board-tpl.c | 2 +- arch/arm/mach-rockchip/rk3399-board-spl.c | 2 +- arch/arm/mach-rockchip/save_boot_param.S | 69 -------------------- 17 files changed, 226 insertions(+), 218 deletions(-) create mode 100644 arch/arm/lib/setjmp.S create mode 100644 arch/arm/lib/setjmp_aarch64.S delete mode 100644 arch/arm/mach-rockchip/save_boot_param.S