xilinx: use get_mem_top() to compute ram_top

Use the get_mem_top function to compute the value of ram_top. This was
earlier done through LMB API's, which are no longer available till
after relocation. Use get_mem_top() instead to compute the ram_top
value.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Michal Simek <michal.simek@amd.com>
Tested-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/20241025172724.195093-3-sughosh.ganu@linaro.org
Signed-off-by: Michal Simek <michal.simek@amd.com>
diff --git a/board/xilinx/common/board.c b/board/xilinx/common/board.c
index 38dd805..e14ed2c 100644
--- a/board/xilinx/common/board.c
+++ b/board/xilinx/common/board.c
@@ -19,6 +19,7 @@
 #include <i2c.h>
 #include <linux/sizes.h>
 #include <malloc.h>
+#include <memtop.h>
 #include <mtd_node.h>
 #include "board.h"
 #include <dm.h>
@@ -676,3 +677,27 @@
 	return 0;
 }
 #endif
+
+#ifndef MMU_SECTION_SIZE
+#define MMU_SECTION_SIZE        (1 * 1024 * 1024)
+#endif
+
+phys_addr_t board_get_usable_ram_top(phys_size_t total_size)
+{
+	phys_size_t size;
+	phys_addr_t reg;
+
+	if (!total_size)
+		return gd->ram_top;
+
+	if (!IS_ALIGNED((ulong)gd->fdt_blob, 0x8))
+		panic("Not 64bit aligned DT location: %p\n", gd->fdt_blob);
+
+	size = ALIGN(CONFIG_SYS_MALLOC_LEN + total_size, MMU_SECTION_SIZE);
+	reg = get_mem_top(gd->ram_base, gd->ram_size, size,
+			  (void *)gd->fdt_blob);
+	if (!reg)
+		reg = gd->ram_top - size;
+
+	return reg + size;
+}