[U-Boot] [PATCH 3/5] sunxi: add 3GiB DRAM detection support in main U-Boot

[André Przywara]

On 07/02/18 19:35, Icenowy Zheng wrote:

Hi,

> Some Allwinner SoCs can use 3GiB DRAM (part of 4GiB or larger module).
> 
> As the common get_ram_size function cannot detect non-pow-of-2 memory,
> add special detect code into the DRAM size code in main U-Boot.

The original get_ram_size() function is slightly dodgy already (as it
probes memory by writing). And in general we will never be able to cover
ARMv7/LPAE machines easily with our current static identify mapping -
regardless of any probing hacks we pull up.

So I was wondering if we could either:
- somehow pass the result of sunxi_dram_init() to U-Boot proper, or
- call the DRAM size determination routine again

This would give us the definite answer, and would be correct in every
case. We just need to limit it to the memory map limit, if any.

But his function below looks really like a hack. If at all, it should be
part of the get_ram_size() routine itself, as this is not sunxi specific.

Cheers,
Andre.


> Signed-off-by: Icenowy Zheng <icenowy at aosc.io>
> ---
>  board/sunxi/board.c            | 23 +++++++++++++++++++++++
>  include/configs/sunxi-common.h |  2 +-
>  2 files changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/board/sunxi/board.c b/board/sunxi/board.c
> index 8891961dcc..8d707cbac2 100644
> --- a/board/sunxi/board.c
> +++ b/board/sunxi/board.c
> @@ -256,7 +256,30 @@ int board_init(void)
>  
>  int dram_init(void)
>  {
> +#if PHYS_SDRAM_0_SIZE == (SZ_2G + SZ_1G)
> +	/*
> +	 * get_ram_size() doesn't support non-pow-of-2 sizes, so the detection
> +	 * of 3GiB DRAM is implemented here.
> +	 * It just checks whether the DRAM is bigger than 2GiB, as the DRAM
> +	 * module is usually 4GiB in this case (and 1GiB is not accessible).
> +	 */
> +	u32 save_0, save_2g;
> +	gd->ram_size = get_ram_size((long *)PHYS_SDRAM_0, SZ_2G);
> +	if (gd->ram_size == SZ_2G) {
> +		save_0 = readl(PHYS_SDRAM_0);
> +		save_2g = readl(PHYS_SDRAM_0 + SZ_2G);
> +		writel(0, PHYS_SDRAM_0);
> +		writel(0xaa55aa55, PHYS_SDRAM_0 + SZ_2G);
> +		dsb();
> +		if (readl(PHYS_SDRAM_0) != readl(PHYS_SDRAM_0 + SZ_2G)) {
> +			gd->ram_size = SZ_2G + SZ_1G;
> +			writel(save_2g, PHYS_SDRAM_0 + SZ_2G);
> +		}
> +		writel(save_0, PHYS_SDRAM_0);
> +	}
> +#else
>  	gd->ram_size = get_ram_size((long *)PHYS_SDRAM_0, PHYS_SDRAM_0_SIZE);
> +#endif
>  
>  	return 0;
>  }
> diff --git a/include/configs/sunxi-common.h b/include/configs/sunxi-common.h
> index 9b3944ad13..177647e009 100644
> --- a/include/configs/sunxi-common.h
> +++ b/include/configs/sunxi-common.h
> @@ -111,7 +111,7 @@
>  
>  #define CONFIG_NR_DRAM_BANKS		1
>  #define PHYS_SDRAM_0			CONFIG_SYS_SDRAM_BASE
> -#define PHYS_SDRAM_0_SIZE		0x80000000 /* 2 GiB */
> +#define PHYS_SDRAM_0_SIZE		CONFIG_SUNXI_DRAM_MAX_SIZE
>  
>  #ifdef CONFIG_AHCI
>  #define CONFIG_SCSI_AHCI_PLAT
>