[U-Boot] [linux-sunxi] [PATCH v2 6/6] sunxi: store DRAM size in SPL header

[Jagan Teki]

On Thu, Oct 25, 2018 at 2:53 PM Icenowy Zheng <icenowy at aosc.io> wrote:
>
> From: Andre Przywara <andre.przywara at arm.com>
>
> At the moment we rely on the infamous get_ram_size() function to learn
> the actual DRAM size in U-Boot proper. This function has two issues:
> 1) It only works if the DRAM size is a power of two. We start to see
> boards which have 3GB of (usable) DRAM, so this does not fit anymore.
> 2) As U-Boot has no notion of reserved memory so far, it will happily
> ride through the DRAM, possibly stepping on secure-only memory. This
> could be a region of DRAM reserved for OP-TEE or some other secure
> payload, for instance. It will most likely crash in that case.
>
> As the SPL DRAM init routine has very accurate knowledge of the actual
> DRAM size, lets propagate this wisdom to U-Boot proper.
> We re-purpose a currently reserved word in our SPL header for that.
> The SPL itself stores the detected DRAM size there, and bumps the SPL
> header version number in that case. U-Boot proper checks for a valid
> SPL header and a high enough version number, then uses the DRAM size
> from there. If the SPL header field is not sufficient, we fall back to
> the old DRAM scanning routine.
>
> Part of the DRAM might be present and probed by SPL, but not accessible
> by the CPU. They're restricted in the main U-Boot binary, when accessing
> the DRAM size from SPL header.
>
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> Signed-off-by: Icenowy Zheng <icenowy at aosc.io>
> ---
> Changes in v2:
> - Restrict the DRAM size to the accessible range.
>
>  arch/arm/include/asm/arch-sunxi/spl.h |  3 ++-
>  board/sunxi/board.c                   | 28 ++++++++++++++++++++++++++-
>  2 files changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/include/asm/arch-sunxi/spl.h b/arch/arm/include/asm/arch-sunxi/spl.h
> index 014184b638..4baba38b00 100644
> --- a/arch/arm/include/asm/arch-sunxi/spl.h
> +++ b/arch/arm/include/asm/arch-sunxi/spl.h
> @@ -19,6 +19,7 @@
>
>  #define SPL_ENV_HEADER_VERSION SPL_VERSION(0, 1)
>  #define SPL_DT_HEADER_VERSION  SPL_VERSION(0, 2)
> +#define SPL_DRAM_HEADER_VERSION        SPL_VERSION(0, 3)
>
>  #define SPL_ADDR               CONFIG_SUNXI_SRAM_ADDRESS
>
> @@ -70,7 +71,7 @@ struct boot_file_head {
>          * to the users.
>          */
>         uint32_t dt_name_offset;        /* since v0.2, set by mksunxiboot */
> -       uint32_t reserved1;
> +       uint32_t dram_size;             /* in MiB, since v0.3, set by SPL */
>         uint32_t boot_media;            /* written here by the boot ROM */
>         /* A padding area (may be used for storing text strings) */
>         uint32_t string_pool[13];       /* since v0.2, filled by mksunxiboot */
> diff --git a/board/sunxi/board.c b/board/sunxi/board.c
> index bdec82b065..65ae0c4219 100644
> --- a/board/sunxi/board.c
> +++ b/board/sunxi/board.c
> @@ -281,7 +281,16 @@ static struct boot_file_head * get_spl_header(uint8_t req_version)
>
>  int dram_init(void)
>  {
> -       gd->ram_size = get_ram_size((long *)PHYS_SDRAM_0, PHYS_SDRAM_0_SIZE);
> +       struct boot_file_head *spl = get_spl_header(SPL_DRAM_HEADER_VERSION);
> +
> +       if (spl == INVALID_SPL_HEADER)
> +               gd->ram_size = get_ram_size((long *)PHYS_SDRAM_0,
> +                                           PHYS_SDRAM_0_SIZE);
> +       else
> +               gd->ram_size = (phys_addr_t)spl->dram_size << 20;

How about checking SPL_DRAM_HEADER_VERSION in valid header case?