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@xxxxxxxxxx>
Works fine on all ARM 32bit Exynos-based boards I have for tests.
Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> ---
> 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
