[PATCH v1] x86: tangier: Find proper memory region for relocation

[Andy Shevchenko]

It appears that U-Boot works by luck on Intel Edison board because the amount
of RAM is less than 1 GB and standard way of calculating the top of it work
for this configuration. However, this won't work if the amount of RAM is
different and split differently in address space. We have to fine the suitable
window correctly.

Find proper memory region for relocation by scanning MMAP SFI table in
board_get_usable_ram_top() callback.

According to the address map documentation the Main Memory is guaranteed to lie
in the 0..2 GB range, that's why we limit search by this range.

Fixes: e71de54a4943 ("x86: Add Intel Tangier support")
Signed-off-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
---
 arch/x86/cpu/tangier/sdram.c | 43 ++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/arch/x86/cpu/tangier/sdram.c b/arch/x86/cpu/tangier/sdram.c
index df3b9e4ec975..afb08476ed3b 100644
--- a/arch/x86/cpu/tangier/sdram.c
+++ b/arch/x86/cpu/tangier/sdram.c
@@ -196,6 +196,49 @@ unsigned int install_e820_map(unsigned int max_entries,
 	return sfi_setup_e820(max_entries, entries);
 }
 
+/*
+ * This function looks for the highest region of memory lower than 2GB which
+ * has enough space for U-Boot where U-Boot is aligned on a page boundary. It
+ * overrides the default implementation found elsewhere which simply picks the
+ * end of RAM, wherever that may be. The location of the stack, the relocation
+ * address, and how far U-Boot is moved by relocation are set in the global
+ * data structure.
+ */
+ulong board_get_usable_ram_top(ulong total_size)
+{
+	struct sfi_table_simple *sb;
+	struct sfi_mem_entry *mentry;
+	ulong dest_addr = 0;
+	u32 i;
+
+	sb = sfi_search_mmap();
+	if (!sb)
+		panic("No available memory found for relocation");
+
+	sfi_for_each_mentry(i, sb, mentry) {
+		unsigned long long start, end;
+
+		if (mentry->type != SFI_MEM_CONV)
+			continue;
+
+		start = mentry->phys_start;
+		end = start + (mentry->pages << 12);
+
+		/* Filter memory over 2GB. */
+		if (end > 0x7fffffffULL)
+			end = 0x80000000ULL;
+		/* Skip this region if it's too small. */
+		if (end - start < total_size)
+			continue;
+
+		/* Use this address if it's the largest so far. */
+		if (end > dest_addr)
+			dest_addr = end;
+	}
+
+	return dest_addr;
+}
+
 int dram_init_banksize(void)
 {
 	sfi_get_bank_size();
-- 
2.29.2