1 files changed, 20 insertions, 0 deletions
diff --git a/arch/riscv/cpu/generic/dram.c b/arch/riscv/cpu/generic/dram.c
index 84d87d2a7f..b7b1207235 100644
--- a/arch/riscv/cpu/generic/dram.c
+++ b/arch/riscv/cpu/generic/dram.c
@@ -5,6 +5,9 @@
 
 #include <common.h>
 #include <fdtdec.h>
+#include <linux/sizes.h>
+
+DECLARE_GLOBAL_DATA_PTR;
 
 int dram_init(void)
 {
@@ -15,3 +18,20 @@ int dram_init_banksize(void)
 {
 	return fdtdec_setup_memory_banksize();
 }
+
+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.
+	 *
+	 * This in-turn ensures that 32bit DMA capable
+	 * devices work fine because DMA mapping APIs will
+	 * provide 32bit DMA addresses only.
+	 */
+	if (gd->ram_top > SZ_4G)
+		return SZ_4G;
+#endif
+	return gd->ram_top;
+}