common: memtop: add logic to detect ram_top

Add generic logic to determine the ram_top value for boards. Earlier,
this was achieved in an indirect manner through a set of LMB API's.
That has since changed so that the LMB code is available only after
relocation. Replace those LMB calls with a single call to
get_mem_top() to determine the value of ram_top.

Signed-off-by: Sughosh Ganu <[email protected]>
Reviewed-by: Michal Simek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Michal Simek <[email protected]>

1 files changed, 22 insertions, 0 deletions

diff --git a/include/memtop.h b/include/memtop.h
new file mode 100644
index 00000000000..28f62e24ea7
--- /dev/null
+++ b/include/memtop.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (c) 2024, Linaro Limited
+ */
+
+/**
+ * get_mem_top() - Compute the value of ram_top
+ * @ram_start:	Start of RAM
+ * @ram_size:	RAM size
+ * @size:	Minimum RAM size requested
+ * @fdt:	FDT blob
+ *
+ * The function computes the top address of RAM memory that can be
+ * used by U-Boot. This is being done by going through the list of
+ * reserved memory regions specified in the devicetree blob passed
+ * to the function. The logic used here is derived from the lmb
+ * allocation function.
+ *
+ * Return: address of ram top on success, 0 on failure
+ */
+phys_addr_t get_mem_top(phys_addr_t ram_start, phys_size_t ram_size,
+			phys_size_t size, void *fdt);