[U-Boot] [PATCH 1/9] dm: allow 4GB of DRAM on 32bit systems

[Simon Glass]

On 26 July 2018 at 07:59, Philipp Tomsich
<philipp.tomsich at theobroma-systems.com> wrote:
> Even on 32bit systems a full 4GB of DRAM may be installed and reported
> by the DRAM controller.  Whether these 4GB are larger available
> depends on the size/configuration of address decoding windows and
> architectural features (e.g. consider a hypothetical architecture that
> uses dedicated instructions to access the 'memory-mapped' peripheral
> IO ranges).  In U-Boot, the available DRAM, as reported by the
> device-model is independent of the accessible DRAM (i.e. adjusted top
> and effective size).
>
> This was first reported against the RK3288, which may have 4GB DRAM
> attached, but will have a small (e.g. 128MB) window not accessible due
> to address decoding limitations.
>
> The solution is to increase the types used for storing the ram_size to
> have at least 33 bits even on 32bit systems... i.e. we need to use a
> u64 for these always (this was previously only the case for
> PHYS_64BIT, which will have unwanted side-effects for 32bit systems
> and would require more intrusive changes).
>
> This commit changes the size-field in 'struct ram' and the ram_size in
> 'gd' to be a u64.
>
> Reported-by: Marty E. Plummer <hanetzer at startmail.com>
> Signed-off-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
> ---
>
>  include/asm-generic/global_data.h | 2 +-
>  include/ram.h                     | 9 ++++++++-
>  2 files changed, 9 insertions(+), 2 deletions(-)
>

Reviewed-by: Simon Glass <sjg at chromium.org>

> diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
> index 0fd4900..f3d687c 100644
> --- a/include/asm-generic/global_data.h
> +++ b/include/asm-generic/global_data.h
> @@ -55,7 +55,7 @@ typedef struct global_data {
>         unsigned long ram_base;         /* Base address of RAM used by U-Boot */
>         unsigned long ram_top;          /* Top address of RAM used by U-Boot */
>         unsigned long relocaddr;        /* Start address of U-Boot in RAM */
> -       phys_size_t ram_size;           /* RAM size */
> +       u64 ram_size;                   /* RAM size */
>         unsigned long mon_len;          /* monitor len */
>         unsigned long irq_sp;           /* irq stack pointer */
>         unsigned long start_addr_sp;    /* start_addr_stackpointer */
> diff --git a/include/ram.h b/include/ram.h
> index 67e22d7..1fe024f 100644
> --- a/include/ram.h
> +++ b/include/ram.h
> @@ -9,7 +9,14 @@
>
>  struct ram_info {
>         phys_addr_t base;
> -       size_t size;
> +       /*
> +        * We use a 64bit type for the size to correctly handle 32bit
> +        * systems with 4GB of DRAM (which would overflow a 32bit type
> +        * and read back as 0).  For 64bit systems, we assume (for now)

forever :-)

> +        * that they will always have less than 2^65 byte of DRAM
> +        * installed. -- prt

Is the prt your signature? I suggest dropping it.

> +        */
> +       u64 size;
>  };
>
>  struct ram_ops {
> --
> 2.1.4
>

Regards,
Simon