rockchip: rk3399: use actual dram size

Since our sdram driver is ready, we can use the actual size
instead of hard code.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/board/rockchip/evb_rk3399/evb-rk3399.c b/board/rockchip/evb_rk3399/evb-rk3399.c
index 6561c4f..e83dedb 100644
--- a/board/rockchip/evb_rk3399/evb-rk3399.c
+++ b/board/rockchip/evb_rk3399/evb-rk3399.c
@@ -5,6 +5,7 @@
  */
 #include <common.h>
 #include <dm.h>
+#include <ram.h>
 #include <dm/pinctrl.h>
 #include <dm/uclass-internal.h>
 #include <asm/arch/periph.h>
@@ -62,7 +63,23 @@
 
 int dram_init(void)
 {
-	gd->ram_size = 0x80000000;
+	struct ram_info ram;
+	struct udevice *dev;
+	int ret;
+
+	ret = uclass_get_device(UCLASS_RAM, 0, &dev);
+	if (ret) {
+		debug("DRAM init failed: %d\n", ret);
+		return ret;
+	}
+	ret = ram_get_info(dev, &ram);
+	if (ret) {
+		debug("Cannot get DRAM size: %d\n", ret);
+		return ret;
+	}
+	debug("SDRAM base=%llx, size=%x\n", ram.base, (unsigned int)ram.size);
+	gd->ram_size = ram.size;
+
 	return 0;
 }