From 0977448b45e2f1a9cbe7d7e11d208b16460c79ea Mon Sep 17 00:00:00 2001 From: Emanuele Ghidoli Date: Fri, 17 Apr 2026 09:13:31 +0200 Subject: 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 appear 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 y0000c000 -> x00010000 y00010000 -> x0000c000 y00014000 -> x00008000 y00018000 -> x00004000 y0001c000 -> x00000000 This helper makes it possible to probe RAM size by explicitly specifying the probed address and the expected alias address for each size check. Signed-off-by: Emanuele Ghidoli Reviewed-by: Simon Glass --- include/init.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include') diff --git a/include/init.h b/include/init.h index 1e375da4893..c31ebd83b85 100644 --- a/include/init.h +++ b/include/init.h @@ -14,6 +14,12 @@ #include +struct ram_alias_check { + void *probe_addr; + void *alias_addr; + long size; +}; + /* * In case of the EFI app the UEFI firmware provides the low-level * initialisation. @@ -88,6 +94,7 @@ int dram_init(void); int dram_init_banksize(void); long get_ram_size(long *base, long size); +long probe_ram_size_by_alias(const struct ram_alias_check *checks); phys_size_t get_effective_memsize(void); int testdram(void); -- cgit v1.2.3