[PATCH v1 1/3] common: memsize: add RAM size probe based on alias detection

[Simon Glass]

Hi Emanuele,

On 2026-04-16T08:45:22, Emanuele Ghidoli <ghidoliemanuele at gmail.com> wrote:
> common: memsize: add RAM size probe based on alias detection
>
> Add probe_ram_size_by_alias() to detect RAM size by checking whether a
> write to one address aliases to another address.
>
> Compared to get_ram_size(), this function allows the caller to:
> - limit probing to a small set of required accesses
> - avoid touching reserved or already used memory regions
> - handle non-linear alias patterns
>
> On the iMX95 SoC, when used with LPDDR5, accesses beyond the end of an 8GB DDR
> configuration do not alias to the expected linear wrap-around addresses.
> Instead, the aliased addresses appears to follow a pattern related to the
> DDRC bank and bank-group addresses mapping. Experimentally, the observed
> pattern is:
>
> Write        Read
> y00000000 -> x0001c000
> y00004000 -> x00018000
> y00008000 -> x00014000
> [...]
>
> common/memsize.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/init.h   |  7 +++++++
>  2 files changed, 63 insertions(+)

> diff --git a/common/memsize.c b/common/memsize.c
> @@ -127,6 +127,62 @@ long get_ram_size(long *base, long maxsize)
> +long probe_ram_size_by_alias(const struct ram_alias_check *checks)
> +{
> +     long save[2];
> +     int dcache_en = dcache_status();

Do we need to check for CONFIG_IS_ENABLED(SYS_DCACHE_OFF) here?

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

Regards,
Simon