linux-kernel - Re: [PATCH v2 1/5] arm64: mm: Move zone_dma_bits initialization into zone_sizes

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Date:   Mon, 12 Oct 2020 12:37:48 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Cc:     robh+dt@...nel.org, hch@....de, ardb@...nel.org,
        linux-kernel@...r.kernel.org, robin.murphy@....com,
        linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org, jeremy.linton@....com,
        iommu@...ts.linux-foundation.org, devicetree@...r.kernel.org,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v2 1/5] arm64: mm: Move zone_dma_bits initialization into
 zone_sizes_init()

On Sat, Oct 10, 2020 at 05:12:31PM +0200, Nicolas Saenz Julienne wrote:
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index f6902a2b4ea6..0eca5865dcb1 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -196,14 +196,16 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
>  	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
>  
>  #ifdef CONFIG_ZONE_DMA
> +	zone_dma_bits = ARM64_ZONE_DMA_BITS;
> +
>  	if (IS_ENABLED(CONFIG_ACPI)) {
>  		extern unsigned int acpi_iort_get_zone_dma_size(void);
>  
>  		zone_dma_bits = min(zone_dma_bits,
>  				    acpi_iort_get_zone_dma_size());
> -		arm64_dma_phys_limit = max_zone_phys(zone_dma_bits);
>  	}
>  
> +	arm64_dma_phys_limit = max_zone_phys(zone_dma_bits);
>  	max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
>  #endif
>  #ifdef CONFIG_ZONE_DMA32
> @@ -394,11 +396,6 @@ void __init arm64_memblock_init(void)
>  
>  	early_init_fdt_scan_reserved_mem();
>  
> -	if (IS_ENABLED(CONFIG_ZONE_DMA)) {
> -		zone_dma_bits = ARM64_ZONE_DMA_BITS;
> -		arm64_dma_phys_limit = max_zone_phys(ARM64_ZONE_DMA_BITS);
> -	}

arm64_dma_phys_limit is used by memblock_alloc_low() (via
ARCH_LOW_ADDRESS_LIMIT). I think it's too late to leave its
initialisation to zone_sizes_init().

-- 
Catalin