On Wed, 2022-02-09 at 13:13 +0000, Andre Przywara wrote:
On Wed, 9 Feb 2022 14:05:57 +0100 Michael Walle michael@walle.cc wrote:
Hi,
The problem I have is that I boot a custom SOC into u-boot and when u-boot tries to boot linux I get an error exception when u-boot calls armv8_switch_to_el2 to enter linux.
So that means that U-Boot runs in EL3, is that the first and only firmware that you run? I think the EL3 part of U-Boot is not widely used and tested beyond the very few platforms that use it.
FWIW, the u-boot on the kontron_sl28 (which is a A72 core) is running in EL3. But it's a layerscape so it might be worth looking in arch/arm/cpu/armv8/fsl-layerscale/ if there is anything special.
Thanks Michael, that's what I meant: the generic EL3 code in arch/arm/cpu/armv8 might depend on more platform specific code to make it work.
Thanks guys, will look at these boards. I have learnt that EL2 state in our design may be broken so I started to look at going directly to EL1 instead, is that a bad idea?
In u-boot I find:
#ifdef CONFIG_ARMV8_SWITCH_TO_EL1 static void switch_to_el1(void) { if ((IH_ARCH_DEFAULT == IH_ARCH_ARM64) && (images.os.arch == IH_ARCH_ARM)) armv8_switch_to_el1(0, (u64)gd->bd->bi_arch_number, (u64)images.ft_addr, 0, (u64)images.ep, ES_TO_AARCH32); else armv8_switch_to_el1((u64)images.ft_addr, 0, 0, 0, images.ep, ES_TO_AARCH64); } #endif .... #ifdef CONFIG_ARMV8_SWITCH_TO_EL1 armv8_switch_to_el2((u64)images->ft_addr, 0, 0, 0, (u64)switch_to_el1, ES_TO_AARCH64); #else .....
which looks promising but when I look closer I see that this seems to do: EL3 -> EL1 -> EL2 Really? What is the point ? Looks like I need to hack something myself to go EL3->EL1 or am I missing something ?
Jocke