[PATCH 1/7] riscv: Adjust board_get_usable_ram_top() for 32-bit

[Bin Meng <bmeng.cn@gmail.com>]

From: Bin Meng <bin.meng@windriver.com>

When testing QEMU RISC-V 'virt' machine with a 2 GiB memory
configuration, it was discovered gd->ram_top is assigned to
value zero in setup_dest_addr().

While gd->ram_top should not be declared as type `unsigned long`,
which will be updated in a future patch, the current logic in
board_get_usable_ram_top() can be updated to cover both 64-bit
and 32-bit RISC-V.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
---

 arch/riscv/cpu/fu540/dram.c   | 7 +++----
 arch/riscv/cpu/generic/dram.c | 7 +++----
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/riscv/cpu/fu540/dram.c b/arch/riscv/cpu/fu540/dram.c
index 1dc77efeca..259da65a54 100644
--- a/arch/riscv/cpu/fu540/dram.c
+++ b/arch/riscv/cpu/fu540/dram.c
@@ -22,7 +22,6 @@ int dram_init_banksize(void)
 
 ulong board_get_usable_ram_top(ulong total_size)
 {
-#ifdef CONFIG_64BIT
 	/*
 	 * Ensure that we run from first 4GB so that all
 	 * addresses used by U-Boot are 32bit addresses.
@@ -31,8 +30,8 @@ ulong board_get_usable_ram_top(ulong total_size)
 	 * devices work fine because DMA mapping APIs will
 	 * provide 32bit DMA addresses only.
 	 */
-	if (gd->ram_top > SZ_4G)
-		return SZ_4G;
-#endif
+	if (gd->ram_top >= SZ_4G)
+		return SZ_4G - 1;
+
 	return gd->ram_top;
 }
diff --git a/arch/riscv/cpu/generic/dram.c b/arch/riscv/cpu/generic/dram.c
index 1dc77efeca..259da65a54 100644
--- a/arch/riscv/cpu/generic/dram.c
+++ b/arch/riscv/cpu/generic/dram.c
@@ -22,7 +22,6 @@ int dram_init_banksize(void)
 
 ulong board_get_usable_ram_top(ulong total_size)
 {
-#ifdef CONFIG_64BIT
 	/*
 	 * Ensure that we run from first 4GB so that all
 	 * addresses used by U-Boot are 32bit addresses.
@@ -31,8 +30,8 @@ ulong board_get_usable_ram_top(ulong total_size)
 	 * devices work fine because DMA mapping APIs will
 	 * provide 32bit DMA addresses only.
 	 */
-	if (gd->ram_top > SZ_4G)
-		return SZ_4G;
-#endif
+	if (gd->ram_top >= SZ_4G)
+		return SZ_4G - 1;
+
 	return gd->ram_top;
 }
-- 
2.25.1