Re: [Xen-devel] [PATCH 09/17] xen/arm64: head: Improve coding style and document cpu_init()

[Stefano Stabellini <sstabellini@kernel.org>]

On Mon, 10 Jun 2019, Julien Grall wrote:
> Adjust the coding style used in the comments within cpu_init(). Take the
> opportunity to alter the early print to match the function name.
> 
> Lastly, document the behavior and the main registers usage within the
> function.
> 
> Signed-off-by: Julien Grall <julien.grall@arm.com>
> ---
>  xen/arch/arm/arm64/head.S | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
> index 6aa3148192..ee0024173e 100644
> --- a/xen/arch/arm/arm64/head.S
> +++ b/xen/arch/arm/arm64/head.S
> @@ -396,19 +396,26 @@ skip_bss:
>          ret
>  ENDPROC(zero_bss)
>  
> +/*
> + * Initialize the processor for turning the MMU on.
> + *
> + * Clobbers x0 - x4

Shouldn't it be x0 - x3?

The rest looks fine.


> + */
>  cpu_init:
> -        PRINT("- Setting up control registers -\r\n")
> +        PRINT("- Initialize CPU -\r\n")
>  
>          /* Set up memory attribute type tables */
>          ldr   x0, =MAIRVAL
>          msr   mair_el2, x0
>  
> -        /* Set up TCR_EL2:
> +        /*
> +         * Set up TCR_EL2:
>           * PS -- Based on ID_AA64MMFR0_EL1.PARange
>           * Top byte is used
>           * PT walks use Inner-Shareable accesses,
>           * PT walks are write-back, write-allocate in both cache levels,
> -         * 48-bit virtual address space goes through this table. */
> +         * 48-bit virtual address space goes through this table.
> +         */
>          ldr   x0, =(TCR_RES1|TCR_SH0_IS|TCR_ORGN0_WBWA|TCR_IRGN0_WBWA|TCR_T0SZ(64-48))
>          /* ID_AA64MMFR0_EL1[3:0] (PARange) corresponds to TCR_EL2[18:16] (PS) */
>          mrs   x1, ID_AA64MMFR0_EL1
> @@ -427,9 +434,11 @@ cpu_init:
>          ldr   x0, =(HSCTLR_BASE)
>          msr   SCTLR_EL2, x0
>  
> -        /* Ensure that any exceptions encountered at EL2
> +        /*
> +         * Ensure that any exceptions encountered at EL2
>           * are handled using the EL2 stack pointer, rather
> -         * than SP_EL0. */
> +         * than SP_EL0.
> +         */
>          msr spsel, #1
>          ret
>  ENDPROC(cpu_init)
> -- 
> 2.11.0
> 

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