[U-Boot] [PATCH] armv8: errata: Implement workaround for Cortex-A53 Erratum 855873

[Andre Przywara]

Hi Alison,

On 20/07/17 03:09, Alison Wang wrote:
> 855873: An eviction might overtake a cache clean operation
> Workaround: The erratum can be avoided by upgrading cache clean by
> address operations to cache clean and invalidate operations. For
> Cortex-A53 r0p3 and later release,

As you mention, this workaround is only viable for r0p3 and above, as
the chicken bit does not exist in prior versions of the core.
So I would feel better if we could have an MIDR check just before
reading CPUACTLR_EL1. This would allow other A53 users to reuse the
errata fixes more easily.

> this can be achieved by setting CPUACTLR.ENDCASCI to 1.

I think the name of the bit is ENDCCASCI (with two C's).

Cheers,
Andre.

> This patch is to implement the workaround for this erratum.
> 
> Signed-off-by: Alison Wang <alison.wang at nxp.com>
> ---
>  arch/arm/Kconfig                          |  3 +++
>  arch/arm/cpu/armv8/fsl-layerscape/Kconfig |  2 ++
>  arch/arm/cpu/armv8/start.S                | 15 ++++++++++++++-
>  3 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index d43aaac..4a885a3 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -103,6 +103,9 @@ config ARM_ERRATA_852421
>  config ARM_ERRATA_852423
>  	bool
>  
> +config ARM_ERRATA_855873
> +	bool
> +
>  config CPU_ARM720T
>  	bool
>  	select SYS_CACHE_SHIFT_5
> diff --git a/arch/arm/cpu/armv8/fsl-layerscape/Kconfig b/arch/arm/cpu/armv8/fsl-layerscape/Kconfig
> index 5825f9b..63658b5 100644
> --- a/arch/arm/cpu/armv8/fsl-layerscape/Kconfig
> +++ b/arch/arm/cpu/armv8/fsl-layerscape/Kconfig
> @@ -1,6 +1,7 @@
>  config ARCH_LS1012A
>  	bool
>  	select ARMV8_SET_SMPEN
> +	select ARM_ERRATA_855873
>  	select FSL_LSCH2
>  	select SYS_FSL_DDR_BE
>  	select SYS_FSL_MMDC
> @@ -11,6 +12,7 @@ config ARCH_LS1012A
>  config ARCH_LS1043A
>  	bool
>  	select ARMV8_SET_SMPEN
> +	select ARM_ERRATA_855873
>  	select FSL_LSCH2
>  	select SYS_FSL_DDR
>  	select SYS_FSL_DDR_BE
> diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
> index 5c500be..3484fd8 100644
> --- a/arch/arm/cpu/armv8/start.S
> +++ b/arch/arm/cpu/armv8/start.S
> @@ -170,7 +170,10 @@ reset_sctrl:
>  WEAK(apply_core_errata)
>  
>  	mov	x29, lr			/* Save LR */
> -	/* For now, we support Cortex-A57 specific errata only */
> +	/* For now, we support Cortex-A53, Cortex-A57 specific errata */
> +
> +	/* Check if we are running on a Cortex-A53 core */
> +	branch_if_a53_core x0, apply_a53_core_errata
>  
>  	/* Check if we are running on a Cortex-A57 core */
>  	branch_if_a57_core x0, apply_a57_core_errata
> @@ -178,6 +181,16 @@ WEAK(apply_core_errata)
>  	mov	lr, x29			/* Restore LR */
>  	ret
>  
> +apply_a53_core_errata:
> +
> +#ifdef CONFIG_ARM_ERRATA_855873
> +	mrs	x0, S3_1_c15_c2_0	/* cpuactlr_el1 */
> +	/* Enable data cache clean as data cache clean/invalidate */
> +	orr	x0, x0, #1 << 44
> +	msr	S3_1_c15_c2_0, x0	/* cpuactlr_el1 */
> +#endif
> +	b 0b
> +
>  apply_a57_core_errata:
>  
>  #ifdef CONFIG_ARM_ERRATA_828024
>