Re: [PATCH 1/2] arm64: mm: update the comments about ZONE_DMA

[Nicolas Saenz Julienne]

On Sat, 2020-12-26 at 11:35 +0800, Chen Zhou wrote:
> Since patchset "arm64: Default to 32-bit wide ZONE_DMA", ZONE_DMA's
> size is fine-tuned. In the absence of addressing limited masters,
> ZONE_DMA will span the whole 32-bit address space, otherwise, in
> the case of the Raspberry Pi 4, it'll only span the 30-bit address
> space. Update the comments.
> 
> Signed-off-by: Chen Zhou <chenzhou10@xxxxxxxxxx>
> ---

Reviewed-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>

>  arch/arm64/mm/init.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 75addb36354a..7b9809e39927 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -53,10 +53,11 @@ s64 memstart_addr __ro_after_init = -1;
>  EXPORT_SYMBOL(memstart_addr);
>  
> 
>  /*
> - * We create both ZONE_DMA and ZONE_DMA32. ZONE_DMA covers the first 1G of
> - * memory as some devices, namely the Raspberry Pi 4, have peripherals with
> - * this limited view of the memory. ZONE_DMA32 will cover the rest of the 32
> - * bit addressable memory area.
> + * We create both ZONE_DMA and ZONE_DMA32. ZONE_DMA's size is fine-tuned.
> + * In the absence of addressing limited masters, ZONE_DMA will span the
> + * whole 32-bit address space, otherwise, in the case of the Raspberry Pi 4,
> + * it'll only span the 30-bit address space. ZONE_DMA32 will cover the rest
> + * of the 32 bit addressable memory area.
>   */
>  phys_addr_t arm64_dma_phys_limit __ro_after_init;
>  static phys_addr_t arm64_dma32_phys_limit __ro_after_init;

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