[PATCH v1] common/memsize.c: Fix get_ram_size() when cache is enabled

[Francesco Dolcini]

From: Emanuele Ghidoli <emanuele.ghidoli at toradex.com>

Ensure that every write is flushed to memory and afterward reads are
from memory.
Since the algorithm rely on the fact that accessing to not existent
memory lead to write at addr / 2 without this modification accesses
to aliased (not physically present) addresses are cached and
wrong size is returned.

This was discovered while working on a TI AM625 based board
where cache is normally enabled, see commit c02712a74849 ("arm: mach-k3: Enable dcache in SPL").

Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli at toradex.com>
Signed-off-by: Francesco Dolcini <francesco.dolcini at toradex.com>
---
 common/memsize.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/common/memsize.c b/common/memsize.c
index 66d5be6a1ff3..f3cd28a06cc6 100644
--- a/common/memsize.c
+++ b/common/memsize.c
@@ -7,6 +7,7 @@
 #include <common.h>
 #include <init.h>
 #include <asm/global_data.h>
+#include <cpu_func.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 
@@ -20,6 +21,16 @@ DECLARE_GLOBAL_DATA_PTR;
 # define sync()		/* nothing */
 #endif
 
+static void dcache_flush_invalidate(volatile long *p)
+{
+	phys_addr_t start, stop;
+
+	start = ALIGN_DOWN((phys_addr_t)p, CONFIG_SYS_CACHELINE_SIZE);
+	stop = start + CONFIG_SYS_CACHELINE_SIZE;
+	flush_dcache_range(start, stop);
+	invalidate_dcache_range(start, stop);
+}
+
 /*
  * Check memory range for valid RAM. A simple memory test determines
  * the actually available RAM size between addresses `base' and
@@ -41,6 +52,7 @@ long get_ram_size(long *base, long maxsize)
 		save[i++] = *addr;
 		sync();
 		*addr = ~cnt;
+		dcache_flush_invalidate(addr);
 	}
 
 	addr = base;
@@ -50,6 +62,8 @@ long get_ram_size(long *base, long maxsize)
 	*addr = 0;
 
 	sync();
+	dcache_flush_invalidate(addr);
+
 	if ((val = *addr) != 0) {
 		/* Restore the original data before leaving the function. */
 		sync();
-- 
2.25.1