[RFC PATCH 1/1] ARM: exynos: only do SMC_CMD_CPU1BOOT call on Exynos4

[Marek Szyprowski]

On 08.01.2022 22:57, Henrik Grimler wrote:
> On Exynos5 the call is simply ignored by most variants of the
> trustzone firmware.  However, on some devices it instead causes the
> device to hang, so let's avoid the call for the SoCs where it should
> not be needed.
>
> To see that the call is ignored, we can look into sboot/tzsw.  On most
> of the Exynos{4,5} devices the part of sboot/tzsw that seem to handle
> the secure monitor calls is quite easy to recognise, the SMC number is
> compared to known ones, and if equal it branches to the relevant
> function.  In assembly this looks something like:
>
> ;-- handle_smc:
> 0x00000514      650070e3       cmn r0, 0x65
> 0x00000518      0a00000a       beq loc.smc_cmd_reg
> 0x0000051c      010070e3       cmn r0, 1
> 0x00000520      6c00000a       beq loc.smc_cmd_init
> 0x00000524      020070e3       cmn r0, 2
> 0x00000528      6b00000a       beq loc.smc_cmd_info
> 0x0000052c      030070e3       cmn r0, 3
> 0x00000530      6e00000a       beq loc.smc_cmd_sleep
> 0x00000534      060070e3       cmn r0, 6
> 0x00000538      ae00000a       beq loc.smc_cmd_save_state
> 0x0000053c      070070e3       cmn r0, 7
> 0x00000540      b400000a       beq loc.smc_cmd_standby
> 0x00000544      2b01001a       bne loc.smc_return_minus1
>
> where above example is from exynos5420-arndale-octa.  As can be seen
> the case where r0 is 4 (i.e. SMC_CMD_CPU1BOOT) is not handled.  The
> annotations are taken from github.com/hsnaves/exynos5410-firmware,
> where a large part of the exynos5410 trustzone firmware has been
> reverse-engineered.
>
> Signed-off-by: Henrik Grimler <henrik at grimler.se>

Works fine on all ARM 32bit Exynos-based boards I have for tests.

Tested-by: Marek Szyprowski <m.szyprowski at samsung.com>

> ---
>   arch/arm/mach-exynos/firmware.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mach-exynos/firmware.c b/arch/arm/mach-exynos/firmware.c
> index 2eaf2dbb8e81..2da5b60b59e2 100644
> --- a/arch/arm/mach-exynos/firmware.c
> +++ b/arch/arm/mach-exynos/firmware.c
> @@ -60,8 +60,10 @@ static int exynos_cpu_boot(int cpu)
>   	/*
>   	 * Exynos3250 doesn't need to send smc command for secondary CPU boot
>   	 * because Exynos3250 removes WFE in secure mode.
> +	 *
> +	 * On Exynos5 devices the call is ignored by trustzone firmware.
>   	 */
> -	if (soc_is_exynos3250())
> +	if (!soc_is_exynos4210() && !soc_is_exynos4412())
>   		return 0;
>   
>   	/*

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland