From 1a2a285a00d5cb7476f33ddaa83e8a91112f7329 Mon Sep 17 00:00:00 2001
From: Evan Lojewski <github@meklort.com>
Date: Sat, 3 Oct 2020 11:21:45 -0600
Subject: NVM: Add an API to determine the NVM size. (#124)

---
 libs/NVRam/include/NVRam.h |  2 ++
 libs/NVRam/nvm.c           | 27 ++++++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

(limited to 'libs')

diff --git a/libs/NVRam/include/NVRam.h b/libs/NVRam/include/NVRam.h
index 919aeb7..5ec5b5f 100644
--- a/libs/NVRam/include/NVRam.h
+++ b/libs/NVRam/include/NVRam.h
@@ -61,6 +61,8 @@ void NVRam_enableWrites(void);
 void NVRam_disable(void);
 void NVRam_disableWrites(void);
 
+uint32_t NVRam_size(void);
+
 uint32_t NVRam_crc(const uint8_t *pcDatabuf, // Pointer to data buffer
                    uint32_t ulDatalen,       // Length of data buffer in bytes
                    uint32_t crc);            // Initial value
diff --git a/libs/NVRam/nvm.c b/libs/NVRam/nvm.c
index 1e4d0cb..e3c33ba 100644
--- a/libs/NVRam/nvm.c
+++ b/libs/NVRam/nvm.c
@@ -45,6 +45,8 @@
 
 #include <NVRam.h>
 
+#define BCM_NVRAM_MAGIC (0x669955AAu)
+
 #define ATMEL_AT45DB0X1B_PAGE_POS (9u)
 #define ATMEL_AT45DB0X1B_PAGE_SIZE (264u)
 #define ATMEL_AT45DB0X1B_ERASE (false)
@@ -90,7 +92,7 @@ static inline uint32_t NVRam_translate(uint32_t address)
     }
     else
     {
-        return address;        
+        return address;
     }
 #else
     return address;
@@ -323,3 +325,26 @@ void NVRam_write(uint32_t address, uint32_t *buffer, uint32_t words)
     }
 #endif
 }
+
+uint32_t NVRam_size(void)
+{
+    size_t size;
+    uint32_t magic = NVRam_readWord(0);
+
+    if (magic != htonl(BCM_NVRAM_MAGIC))
+    {
+        // Unable to determine the size.
+        return 0;
+    }
+
+    // Scan for the magic wrapping around, starting at 2KB flash size.
+    size = 2u * 1024u;
+    do
+    {
+        size *= 2;
+
+        magic = NVRam_readWord(size);
+    } while (magic != htonl(BCM_NVRAM_MAGIC));
+
+    return size;
+}
-- 
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