[PATCH] rockchip: sdram: Fix initialization of DRAM banks

[Jonas Karlman]

The commit 55a342176984 ("common: Add an option to relocate on ram top")
changed so that dram_init_banksize() is called before gd->ram_top has
been initialized. This change broke Rockchip DRAM banks configuration
due to gd->ram_top now being 0 when dram_init_banksize() is called.

This makes first DRAM bank size calculation overflow and end up with

  DRAM bank   = 0x0000000000000000
  -> start    = 0x0000000000200000
  -> size     = 0xffffffffffe00000

instead of the expected (for 2 GiB)

  DRAM bank   = 0x0000000000000000
  -> start    = 0x0000000000200000
  -> size     = 0x000000007fe00000

or (for 4 GiB)

  DRAM bank   = 0x0000000000000000
  -> start    = 0x0000000000200000
  -> size     = 0x00000000f7e00000

on e.g. RK3399 boards.

Change to not depend on gd->ram_top having to be pre-calculated before
dram_init_banksize() is called, also move the related method
board_get_usable_ram_top() closer to more easily get an overview of
their interdependence, to restore working DRAM bank initialization.

Fixes: 55a342176984 ("common: Add an option to relocate on ram top")
Signed-off-by: Jonas Karlman <jonas at kwiboo.se>
---
 arch/arm/mach-rockchip/sdram.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/arm/mach-rockchip/sdram.c b/arch/arm/mach-rockchip/sdram.c
index f0923186fa61..2e404df1b200 100644
--- a/arch/arm/mach-rockchip/sdram.c
+++ b/arch/arm/mach-rockchip/sdram.c
@@ -294,10 +294,20 @@ __weak int rockchip_dram_init_banksize_fixup(struct bd_info *bd)
 	return 0;
 }
 
+phys_addr_t board_get_usable_ram_top(phys_size_t total_size)
+{
+	/* Make sure U-Boot only uses the space below the 4G address boundary */
+	u64 usable_top = min_t(u64, CFG_SYS_SDRAM_BASE + SDRAM_MAX_SIZE, SZ_4G);
+
+	return (gd->ram_top > usable_top) ? usable_top : gd->ram_top;
+}
+
 int dram_init_banksize(void)
 {
-	size_t ram_top = (unsigned long)(gd->ram_size + CFG_SYS_SDRAM_BASE);
-	size_t top = min((unsigned long)ram_top, (unsigned long)(gd->ram_top));
+	/* Make sure first bank uses the space below the 4G address boundary */
+	u64 usable_top = min_t(u64, CFG_SYS_SDRAM_BASE + SDRAM_MAX_SIZE, SZ_4G);
+	size_t ram_top = (unsigned long)(CFG_SYS_SDRAM_BASE + gd->ram_size);
+	size_t top = min((unsigned long)ram_top, (unsigned long)(usable_top));
 
 #ifdef CONFIG_ARM64
 	int ret = rockchip_dram_init_banksize();
@@ -507,11 +517,3 @@ int dram_init(void)
 
 	return 0;
 }
-
-phys_addr_t board_get_usable_ram_top(phys_size_t total_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;
-}
-- 
2.54.0