[U-Boot] [PATCH] armv8: aarch64: Fix the warning about x1-x3 nonzero issue

[Alison Wang]

Hi, Ryan,

	This patch is to fix the issue about a warning for ARMv8 64-bit kernel you reported before. I have tested on my LayerScape boards. Please review and try on your boards too.

	Thanks.


Best Regards,
Alison Wang

> -----Original Message-----
> From: Alison Wang [mailto:b18965 at freescale.com]
> Sent: Friday, January 13, 2017 3:50 PM
> To: york sun <york.sun at nxp.com>; ryan.harkin at linaro.org; agraf at suse.de;
> Scott Wood <scott.wood at nxp.com>; Stuart Yoder <stuart.yoder at nxp.com>;
> Leo Li <leoyang.li at nxp.com>; fenghua at phytium.com.cn;
> linus.walleij at linaro.org; u-boot at lists.denx.de
> Cc: Jason Jin <jason.jin at nxp.com>; Alison Wang <alison.wang at nxp.com>
> Subject: [PATCH] armv8: aarch64: Fix the warning about x1-x3 nonzero
> issue
> 
> For 64-bit kernel, there is a warning about x1-x3 nonzero in violation
> of boot protocol. x3 should be reset to zero before jumping to the
> kernel.
> 
> This patch will adjust the parameters to transfer and make sure x3 is
> zero.
> 
> Signed-off-by: Alison Wang <alison.wang at nxp.com>
> ---
>  arch/arm/cpu/armv8/transition.S | 44
> +++++++++++++++++++++++++++++++++++++----
>  1 file changed, 40 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/cpu/armv8/transition.S
> b/arch/arm/cpu/armv8/transition.S index adb9f35..06b6664 100644
> --- a/arch/arm/cpu/armv8/transition.S
> +++ b/arch/arm/cpu/armv8/transition.S
> @@ -26,9 +26,27 @@ ENTRY(armv8_switch_to_el2)
>  	 * if CONFIG_ARMV8_SWITCH_TO_EL1 is defined.
>           * When running in EL2 now, jump to the
>  	 * address saved in x3.
> +	 *
> +	 * For 64-bit kernel, there is a warning about
> +	 * x1-x3 nonzero in violation of boot protocol.
> +	 * x3 should be reset to zero before jumping to
> +	 * the kernel. Use x4 instead of x3 as parameter.
>  	 */
> -	br x3
> -1:	armv8_switch_to_el2_m x3, x4, x5
> +	mov x4, x3
> +	mov x3, #0
> +	br x4
> +1:
> +	/*
> +	 * For 64-bit kernel, there is a warning about
> +	 * x1-x3 nonzero in violation of boot protocol.
> +	 * x3 should be reset to zero before jumping to
> +	 * the kernel. Use x4, x5, x6 instead of x3, x4,
> +	 * x5 as parameters.
> +	 */
> +	mov x5, x4
> +	mov x4, x3
> +	mov x3, #0
> +	armv8_switch_to_el2_m x4, x5, x6
>  ENDPROC(armv8_switch_to_el2)
> 
>  ENTRY(armv8_switch_to_el1)
> @@ -36,9 +54,27 @@ ENTRY(armv8_switch_to_el1)
>  0:
>  	/* x3 is kernel entry point. When running in EL1
>  	 * now, jump to the address saved in x3.
> +	 *
> +	 * For 64-bit kernel, there is a warning about
> +	 * x1-x3 nonzero in violation of boot protocol.
> +	 * x3 should be reset to zero before jumping to
> +	 * the kernel. Use x4 instead of x3 as parameter.
> +	 */
> +	mov x4, x3
> +	mov x3, #0
> +	br x4
> +1:
> +	/*
> +	 * For 64-bit kernel, there is a warning about
> +	 * x1-x3 nonzero in violation of boot protocol.
> +	 * x3 should be reset to zero before jumping to
> +	 * the kernel. Use x4, x5, x6 instead of x3, x4,
> +	 * x5 as parameters.
>  	 */
> -	br x3
> -1:	armv8_switch_to_el1_m x3, x4, x5
> +	mov x5, x4
> +	mov x4, x3
> +	mov x3, #0
> +	armv8_switch_to_el1_m x4, x5, x6
>  ENDPROC(armv8_switch_to_el1)
> 
>  WEAK(armv8_el2_to_aarch32)
> --
> 2.1.0.27.g96db324