[PATCH] Fix detection of odd memory configurations on sunxi

[Rudi Horn]

Hello,

I encountered a bug where u-boot detects that my OrangePI zero 3 (with 
1.5GB)
has 2GB and crashes. The orangepi u-boot source code contains an additional
modification in the `mctl_calc_size` which removes a quarter of the 
memory the
calculated last address cannot be written to:

https://github.com/orangepi-xunlong/u-boot-orangepi/blob/v2024.01/arch/arm/mach-sunxi/dram_sun50i_h616.c#L1365-L1368

I'm not entirely sure if there is some specific logic that applies to this
modifier, but it does fix the issue on my system.

I propose the following patch, but am open to any further suggestions.

Thanks,
Rudi Horn

Note: Submitted in my personal capacity and is not affiliated with my 
employer.


 From 2199f3b28e5fc853ed1921586358c33f3f1502d3 Mon Sep 17 00:00:00 2001
From: Rudi Horn <dyn-git at rudi-horn.de>
Date: Mon, 11 Aug 2025 08:58:34 +0200
Subject: [PATCH] arch: arm: mach-sonxi: Fix detection of odd memory
  configurations

Fix detection of odd memory configurations. Previously 1.5GB devices were
incorrectly detected as 2GB devices, causing u-boot to crash.

Signed-off-by: Rudi Horn <dyn-git at rudi-horn.de>
---
  arch/arm/include/asm/arch-sunxi/dram.h |  1 +
  arch/arm/mach-sunxi/dram_dw_helpers.c  | 10 +++++++++-
  arch/arm/mach-sunxi/dram_helpers.c     |  8 ++++++++
  3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/arch-sunxi/dram.h 
b/arch/arm/include/asm/arch-sunxi/dram.h
index 0eccb1e6c28..7580421ca77 100644
--- a/arch/arm/include/asm/arch-sunxi/dram.h
+++ b/arch/arm/include/asm/arch-sunxi/dram.h
@@ -44,6 +44,7 @@
  unsigned long sunxi_dram_init(void);
  void mctl_await_completion(u32 *reg, u32 mask, u32 val);
  bool mctl_mem_matches(u32 offset);
+bool mctl_mem_matches_upto(u32 offset);
  bool mctl_mem_matches_base(u32 offset, ulong base);

  #endif /* _SUNXI_DRAM_H */
diff --git a/arch/arm/mach-sunxi/dram_dw_helpers.c 
b/arch/arm/mach-sunxi/dram_dw_helpers.c
index 24767354935..5bcd2672465 100644
--- a/arch/arm/mach-sunxi/dram_dw_helpers.c
+++ b/arch/arm/mach-sunxi/dram_dw_helpers.c
@@ -146,5 +146,13 @@ unsigned long mctl_calc_size(const struct 
dram_config *config)
         u8 width = config->bus_full_width ? 4 : 2;

         /* 8 banks */
-       return (1ULL << (config->cols + config->rows + 3)) * width * 
config->ranks;
+       unsigned long size = (1ULL << (config->cols + config->rows + 3)) 
* width * config->ranks;
+
+       /* some memory configurations such as 1.5GB rely on this to 
compute the correct size */
+       if (!mctl_mem_matches_upto(size)) {
+               size = (size * 3) / 4;
+               debug("capping memory at 0x%lx\n", size);
+       }
+
+  return size;
  }
diff --git a/arch/arm/mach-sunxi/dram_helpers.c 
b/arch/arm/mach-sunxi/dram_helpers.c
index 83dbe4ca98f..68c75fa07a6 100644
--- a/arch/arm/mach-sunxi/dram_helpers.c
+++ b/arch/arm/mach-sunxi/dram_helpers.c
@@ -61,4 +61,12 @@ bool mctl_mem_matches(u32 offset)
  {
         return mctl_mem_matches_base(offset, CFG_SYS_SDRAM_BASE);
  }
+
+/*
+ * Test if memory at offset matches memory at end of DRAM
+ */
+bool mctl_mem_matches_upto(u32 offset)
+{
+       return mctl_mem_matches_base(offset - sizeof(u32), 
CFG_SYS_SDRAM_BASE);
+}
  #endif
--
2.43.0