Am 18.02.20 um 16:37 schrieb Sascha Hauer:
> It seems running from the NFC SRAM doesn't work with the instruction
> cache enabled, it leads to corruptions on the i.MX27. We stumbled upon
> this earlier and the solution at that time was to disable the
> instruction cache in the NAND boot code. It is, however, more reliable
> to just not enable the instruction cache in the first place.
> This is not particularly nice as we have to ifdef this in generic code,
> duplicate arm_cpu_lowlevel_init(), or call arm_cpu_lowlevel_init() later
> when we are out of NFC SRAM. From the different bad solutions I chose
> to ifdef the instruction cache away. It will be enabled later in the
> common cache functions.


Hm... is it possible that we have similar speculation issues as on i.MX6UL? The CPU was speculating
in to IOMEM, caused cache poisoning/corruption and executed corrupted cache.

> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  arch/arm/cpu/lowlevel.S                | 2 ++
>  arch/arm/mach-imx/external-nand-boot.c | 9 ---------
>  2 files changed, 2 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/arm/cpu/lowlevel.S b/arch/arm/cpu/lowlevel.S
> index 3b52644e43..203a4afc47 100644
> --- a/arch/arm/cpu/lowlevel.S
> +++ b/arch/arm/cpu/lowlevel.S
> @@ -57,8 +57,10 @@ THUMB(	orr	r12, r12, #PSR_T_BIT	)
>  	bic	r12, r12, #(CR_M | CR_C | CR_B)
>  	bic	r12, r12, #(CR_S | CR_R | CR_V)
>  
> +#ifndef CONFIG_ARCH_IMX_EXTERNAL_BOOT_NAND
>  	/* enable instruction cache */
>  	orr	r12, r12, #CR_I
> +#endif
>  
>  #if __LINUX_ARM_ARCH__ >= 6
>  	orr	r12, r12, #CR_U
> diff --git a/arch/arm/mach-imx/external-nand-boot.c b/arch/arm/mach-imx/external-nand-boot.c
> index de8e0ffe5d..bf683de858 100644
> --- a/arch/arm/mach-imx/external-nand-boot.c
> +++ b/arch/arm/mach-imx/external-nand-boot.c
> @@ -308,12 +308,6 @@ static void BARE_INIT_FUNCTION(imx35_nand_load_image)(void)
>  static void __noreturn BARE_INIT_FUNCTION(imx##soc##_boot_nand_external_cont)  \
>  			(void *boarddata)				\
>  {									\
> -	uint32_t r;							\
> -									\
> -	r = get_cr();							\
> -	r |= CR_I;							\
> -	set_cr(r);							\
> -									\
>  	imx##soc##_nand_load_image();					\
>  									\
>          imx##soc##_barebox_entry(boarddata);				\
> @@ -331,9 +325,6 @@ void __noreturn BARE_INIT_FUNCTION(imx##soc##_barebox_boot_nand_external) \
>  	int i;								\
>  	void __noreturn (*fn)(void *);					\
>  									\
> -	r = get_cr();							\
> -	r &= ~CR_I;							\
> -	set_cr(r);							\
>  	/* skip NAND boot if not running from NFC space */		\
>  	r = get_pc();							\
>  	if (r < nfc_base || r > nfc_base + 0x800)			\
>