Re: [PATCH v3 2/3] rockchip: sdram: Limit usable ram_top to max 4G

[Kever Yang]

On 2025/1/31 06:07, Jonas Karlman wrote:

U-Boot only works correctly when it uses RAM below the 4G address
boundary on Rockchip SoCs. Limit usable gd->ram_top to max 4G.

Signed-off-by: Jonas Karlman <jo...@kwiboo.se>

Reviewed-by: Kever Yang <kever.y...@rock-chips.com>

Thanks,
- Kever

---
v3: Use u64 to fix 32-bit overflow
v2: New patch
---
  arch/arm/mach-rockchip/sdram.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-rockchip/sdram.c b/arch/arm/mach-rockchip/sdram.c
index 96a791bda2c3..4b8b6b9da7c5 100644
--- a/arch/arm/mach-rockchip/sdram.c
+++ b/arch/arm/mach-rockchip/sdram.c
@@ -487,7 +487,8 @@ int dram_init(void)

phys_addr_t board_get_usable_ram_top(phys_size_t total_size)

  {
-       unsigned long top = CFG_SYS_SDRAM_BASE + SDRAM_MAX_SIZE;
+       /* Make sure U-Boot only uses the space below the 4G address boundary */
+       u64 top = min_t(u64, CFG_SYS_SDRAM_BASE + SDRAM_MAX_SIZE, SZ_4G);

return (gd->ram_top > top) ? top : gd->ram_top;

  }