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Message-ID: <20111023115957.GD17912@n2100.arm.linux.org.uk>
Date: Sun, 23 Oct 2011 12:59:57 +0100
From: Russell King - ARM Linux <linux@....linux.org.uk>
To: Catalin Marinas <catalin.marinas@....com>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v7 15/16] ARM: LPAE: add support for ATAG_MEM64
On Wed, Aug 10, 2011 at 04:03:38PM +0100, Catalin Marinas wrote:
> From: Will Deacon <will.deacon@....com>
>
> LPAE provides support for memory banks with physical addresses of up
> to 40 bits.
>
> This patch adds a new atag, ATAG_MEM64, so that the Kernel can be
> informed about memory that exists above the 4GB boundary.
>
> Signed-off-by: Will Deacon <will.deacon@....com>
> Signed-off-by: Catalin Marinas <catalin.marinas@....com>
> ---
> arch/arm/include/asm/setup.h | 8 ++++++++
> arch/arm/kernel/setup.c | 10 ++++++++++
> 2 files changed, 18 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/include/asm/setup.h b/arch/arm/include/asm/setup.h
> index 915696d..a3ca303 100644
> --- a/arch/arm/include/asm/setup.h
> +++ b/arch/arm/include/asm/setup.h
> @@ -43,6 +43,13 @@ struct tag_mem32 {
> __u32 start; /* physical start address */
> };
>
> +#define ATAG_MEM64 0x54420002
> +
> +struct tag_mem64 {
> + __u64 size;
> + __u64 start; /* physical start address */
> +};
> +
> /* VGA text type displays */
> #define ATAG_VIDEOTEXT 0x54410003
>
> @@ -148,6 +155,7 @@ struct tag {
> union {
> struct tag_core core;
> struct tag_mem32 mem;
> + struct tag_mem64 mem64;
> struct tag_videotext videotext;
> struct tag_ramdisk ramdisk;
> struct tag_initrd initrd;
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index 70bca64..a126558 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -608,6 +608,16 @@ static int __init parse_tag_mem32(const struct tag *tag)
>
> __tagtable(ATAG_MEM, parse_tag_mem32);
>
> +#ifdef CONFIG_PHYS_ADDR_T_64BIT
> +static int __init parse_tag_mem64(const struct tag *tag)
> +{
> + /* We only use 32-bits for the size. */
> + return arm_add_memory(tag->u.mem64.start, (unsigned long)tag->u.mem64.size);
> +}
> +
> +__tagtable(ATAG_MEM64, parse_tag_mem64);
> +#endif /* CONFIG_PHYS_ADDR_T_64BIT */
> +
We should allow this even on 32-bit only kernels - but avoiding adding
>32-bit memory to the system in that case.
--
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