u-boot/arch/arm/cpu
Andre Przywara 0e4d5db4e0 sunxi: Add arm64 FEL support
So far we did not support the BootROM based FEL USB debug mode on the
64-bit builds for Allwinner SoCs: The BootROM is using AArch32, but the
SPL runs in AArch64.
Returning back to AArch32 was not working as expected, since the RMR
reset into 32-bit mode always starts execution in the BootROM, but not
in the FEL routine.

After some debug and research and with help via IRC, the CPU hotplug
mechanism emerged as a solution: If a certain R_CPUCFG register contains
some magic, the BootROM will immediately branch to an address stored in
some other register. This works well for our purposes.

Enable the FEL feature by providing early AArch32 code to first save the
FEL state, *before* initially entering AArch64.
If we eventually determine that we should return to FEL, we reset back
into AArch32, and use the CPU hotplug mechanism to run some small
AArch32 code snippet that restores the initially saved FEL state.

That allows the normal AArch64 SPL build to be loaded via the sunxi-fel
tool, with it returning into FEL mode, so that other payloads can be
transferred via FEL as well.

Tested on A64, H5 and H6.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Tested-by: Icenowy Zheng <icenowy@aosc.io>
Acked-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Priit Laes <plaes@plaes.org> (on Olimex A64-Olinuxino)
2021-01-11 23:19:34 +00:00
..
arm11 common: Drop net.h from common header 2020-05-18 17:33:31 -04:00
arm720t rename symbol: CONFIG_TEGRA -> CONFIG_ARCH_TEGRA 2020-05-15 14:47:35 -04:00
arm920t common: Drop linux/delay.h from common header 2020-05-18 21:19:23 -04:00
arm926ejs treewide: convert bd_t to struct bd_info by coccinelle 2020-07-17 09:30:13 -04:00
arm946es common: Move enable/disable_interrupts out of common.h 2019-12-02 18:25:01 -05:00
arm1136 treewide: convert bd_t to struct bd_info by coccinelle 2020-07-17 09:30:13 -04:00
arm1176 SPDX: Convert all of our single license tags to Linux Kernel style 2018-05-07 09:34:12 -04:00
armv7 Driver model: make some udevice fields private 2021-01-05 22:34:43 -05:00
armv7m common: Drop linux/bitops.h from common header 2020-05-18 21:19:23 -04:00
armv8 sunxi: Add arm64 FEL support 2021-01-11 23:19:34 +00:00
pxa common: Drop linux/delay.h from common header 2020-05-18 21:19:23 -04:00
sa1100 common: Drop linux/delay.h from common header 2020-05-18 21:19:23 -04:00
Makefile SPDX: Convert all of our single license tags to Linux Kernel style 2018-05-07 09:34:12 -04:00
u-boot-spl.lds spl: fix linker size check off-by-one errors 2019-05-05 08:48:50 -04:00
u-boot.lds ARM: Specify aligned address for secure section instead of using attributes 2018-09-07 09:11:42 -04:00