Re: [PATCH] arm: mxs: Clear CPSR V bit to activate low vectors

[Lukasz Majewski <lukma@denx.de>]

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On Sat, 29 Jul 2023 15:30:10 +0200
Marek Vasut <marex@denx.de> wrote:

> The MXS starts with CPSR V bit set, which makes the CPU jump to high
> vectors in case of an exception. Those high vectors are located at
> 0xffff0000, which is where the BootROM exception table is located as
> well. U-Boot should handle exceptions on its own using its own
> exception handling code, which is located at 0x0, i.e. at low
> vectors. Clear the CPSR V bit, so that the CPU would jump to low
> vectors on exception instead, and therefore run the U-Boot exception
> handling code.
> 
> Signed-off-by: Marek Vasut <marex@denx.de>
> ---
> Cc: "NXP i.MX U-Boot Team" <uboot-imx@nxp.com>
> Cc: Fabio Estevam <festevam@gmail.com>
> Cc: Lukasz Majewski <lukma@denx.de>
> Cc: Stefano Babic <sbabic@denx.de>
> ---
>  arch/arm/cpu/arm926ejs/mxs/mxs.c      | 3 +++
>  arch/arm/cpu/arm926ejs/mxs/spl_boot.c | 4 ++++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/arch/arm/cpu/arm926ejs/mxs/mxs.c
> b/arch/arm/cpu/arm926ejs/mxs/mxs.c index 4d21e3df76e..d64a8328b04
> 100644 --- a/arch/arm/cpu/arm926ejs/mxs/mxs.c
> +++ b/arch/arm/cpu/arm926ejs/mxs/mxs.c
> @@ -85,6 +85,9 @@ void mx28_fixup_vt(uint32_t start_addr)
>  		/* cppcheck-suppress nullPointer */
>  		vt[i + 8] = start_addr + (4 * i);
>  	}
> +
> +	/* Make sure ARM core points to low vectors */
> +	set_cr(get_cr() & ~CR_V);
>  }
>  
>  #ifdef	CONFIG_ARCH_MISC_INIT
> diff --git a/arch/arm/cpu/arm926ejs/mxs/spl_boot.c
> b/arch/arm/cpu/arm926ejs/mxs/spl_boot.c index
> 5598c552ab9..4a7dfc6a2ae 100644 ---
> a/arch/arm/cpu/arm926ejs/mxs/spl_boot.c +++
> b/arch/arm/cpu/arm926ejs/mxs/spl_boot.c @@ -17,6 +17,7 @@
>  #include <asm/arch/sys_proto.h>
>  #include <asm/gpio.h>
>  #include <asm/sections.h>
> +#include <asm/system.h>
>  #include <linux/compiler.h>
>  
>  #include "mxs_init.h"
> @@ -104,6 +105,9 @@ static void mxs_spl_fixup_vectors(void)
>  
>  	/* cppcheck-suppress nullPointer */
>  	memcpy(0x0, &_start, 0x60);
> +
> +	/* Make sure ARM core points to low vectors */
> +	set_cr(get_cr() & ~CR_V);
>  }
>  
>  static void mxs_spl_console_init(void)

Reviewed-by: Lukasz Majewski <lukma@denx.de>


Best regards,

Lukasz Majewski

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