Re: [PATCH 01/13] mach-snapdragon: Fix EL2 boot on DragonBoard 410c

[Neil Armstrong <neil.armstrong@linaro.org>]

On 07/04/2025 18:59, Stephan Gerhold wrote:
> The workaround for the "PSCI bug" on DragonBoard 410c implemented in
> arch/arm/mach-snapdragon/include/mach/boot0.h clobbers the x0 register
> by storing the CurrentEL in there. When running in EL1, the mode switch
> sequence implemented there later clears the register again, but this is
> skipped when U-Boot is booted in EL2.
> 
> This causes crashes in the mach-snapdragon board_fdt_blob_setup() later,
> because the invalid address stored in x0 gets dereferenced to check if it
> points to a valid DTB.
> 
> We can't rely on having a valid values in the CPU registers for the first
> stage bootloader configuration on DB410c, and nothing would place a DTB
> there anyway. Skip selecting the SAVE_PREV_BL_FDT_ADDR option for the boot0
> hook case to avoid crashing with the clobbered register value.
> 
> Fixes: 059d526af312 ("mach-snapdragon: generalise board support")
> Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
> ---
>   arch/arm/Kconfig | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 63aefeda9575fec8fc57194358df0819397d088e..af3d39196ee4fb201d4aad20a882bbbb39263396 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -1115,7 +1115,7 @@ config ARCH_SNAPDRAGON
>   	select SPMI
>   	select BOARD_LATE_INIT
>   	select OF_BOARD
> -	select SAVE_PREV_BL_FDT_ADDR
> +	select SAVE_PREV_BL_FDT_ADDR if !ENABLE_ARM_SOC_BOOT0_HOOK
>   	select LINUX_KERNEL_IMAGE_HEADER if !ENABLE_ARM_SOC_BOOT0_HOOK
>   	select SYSRESET
>   	select SYSRESET_PSCI
> 

Good catch

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>