Re: [PATCH master] ARM: i.MX7: enable caches when booted over USB

[Marco Felsch <m.felsch@pengutronix.de>]

Hi,

On 22-09-30, Johannes Zink wrote:
> From: Ahmad Fatoum <a.fatoum@pengutronix.de>
> 
> BootROM on the i.MX7 doesn't set the SMP bit when booted
> over serial download. This leads to vastly worse performance
> when doing memory-heavy operations in a USB-booted system,
> as the caches are not utilized. Example running md5sum over
> a 25M image in ramfs:
> 
>   without patch: 10796ms
>   with    patch: 457ms
> 
> This issue isn't unique to the i.MX7, but exists for the i.MX6UL as
> well, which also has the Cortex-A7 as CPU. Like with
> imx6ul_cpu_lowlevel_init(), adapt imx7_cpu_lowlevel_init() to avoid this
> slow down.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> Signed-off-by: Johannes Zink <j.zink@pengutronix.de>
> ---
>  arch/arm/mach-imx/cpu_init.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-imx/cpu_init.c b/arch/arm/mach-imx/cpu_init.c
> index ea36215419..ede2076102 100644
> --- a/arch/arm/mach-imx/cpu_init.c
> +++ b/arch/arm/mach-imx/cpu_init.c
> @@ -49,7 +49,7 @@ void imx6ul_cpu_lowlevel_init(void)
>  
>  void imx7_cpu_lowlevel_init(void)
>  {
> -	arm_cpu_lowlevel_init();
> +	cortex_a7_lowlevel_init();

Out of curiosity, arm_cpu_lowlevel_init() does a lot more than
cortex_a7_lowlevel_init() e.g. cache invalidation. Is it save to only
call cortex_a7_lowlevel_init() here?

Regards,
  Marco

>  	imx_cpu_timer_init(IOMEM(MX7_SYSCNT_CTRL_BASE_ADDR));
>  }
>  
> -- 
> 2.30.2
> 
> 
>