[U-Boot] [PATCH 1/2] armv8: Enable CPUECTLR.SMPEN for coherency

[Masahiro Yamada]

2016-12-15 15:08 GMT+09:00 Zhiqiang Hou <Zhiqiang.Hou at nxp.com>:
> From: Mingkai Hu <mingkai.hu at nxp.com>
>
> For A53, data coherency is enabled only when the CPUECTLR.SMPEN bit is
> set. The SMPEN bit should be set before enabling the data cache.
> If not enabled, the cache is not coherent with other cores and
> data corruption could occur.
>
> For A57/A72, SMPEN bit enables the processor to receive instruction
> cache and TLB maintenance operations broadcast from other processors
> in the cluster. This bit should be set before enabling the caches and
> MMU, or performing any cache and TLB maintenance operations.
>
> Signed-off-by: Mingkai Hu <mingkai.hu at nxp.com>
> Signed-off-by: Gong Qianyu <Qianyu.Gong at nxp.com>
> Signed-off-by: Mateusz Kulikowski <mateusz.kulikowski at gmail.com>
> Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou at nxp.com>
> ---
>  arch/arm/cpu/armv8/Kconfig | 12 ++++++++++++
>  arch/arm/cpu/armv8/start.S | 11 +++++++++++
>  2 files changed, 23 insertions(+)
>
> diff --git a/arch/arm/cpu/armv8/Kconfig b/arch/arm/cpu/armv8/Kconfig
> index 965a8d1..ce749f2 100644
> --- a/arch/arm/cpu/armv8/Kconfig
> +++ b/arch/arm/cpu/armv8/Kconfig
> @@ -3,6 +3,18 @@ if ARM64
>  config ARMV8_MULTIENTRY
>          bool "Enable multiple CPUs to enter into U-Boot"
>
> +config ARMV8_SET_SMPEN
> +        bool "Enable data coherency with other cores in cluster"
> +        help
> +          Cortex A53/57/72 cores require CPUECTLR_EL1.SMPEN set even
> +          for single core systems. Unfortunately write access to this
> +          register may be controlled by EL3/EL2 firmware. To be more
> +          precise, by default (if there is EL2/EL3 firmware running)
> +          this register is RO for NS EL1.
> +          This switch can be used to avoid writing to CPUECTLR_EL1,
> +          it can be safely enabled when El2/EL3 initialized SMPEN bit
> +          or when CPU implementation doesn't include that register.
> +


If you run ARM Trusted Firmware, this bit has already been
set correctly. (or if you implement your own trusted firmware,
this bit should be set there.)
In those cases, there is no need to touch it in U-Boot.


The motivation for this commit is
to boot the system without any firmware before U-Boot?




-- 
Best Regards
Masahiro Yamada