Fix flash ecc issue on MAX32657

Erasing flash will also erase the ECC bits. These bits are not
updated until a flash write. Reading from erased memory will
signal a ECC error that is falsely corrected from 0xFF to 0xFD
on the 16th byte of each 128-bit line.

This commit applies a workaround by setting the 16th byte of each
line to 0xFF to handle this issue on max32657.

Co-authored-by: Mert Vatansever <[email protected]>
Co-authored-by: Kevin Gillespie <[email protected]>

Libraries/PeriphDrivers/Source/FLC/flc_me30.c

@@ -233,6 +233,38 @@ int MXC_FLC_Write(uint32_t address, uint32_t length, uint32_t *buffer)
 void MXC_FLC_Read(int address, void *buffer, int len)
 {
     MXC_FLC_Com_Read(address, buffer, len);
+
+    /* ECC error detected */
+    if (MXC_GCR->eccerr & MXC_F_GCR_ECCERR_FLASH) {
+
+        /* Clear the ECC error */
+        MXC_GCR->eccerr = MXC_F_GCR_ECCERR_FLASH;
+
+        /*
+         * Erasing flash will also erase the ECC bits. These bits are not
+         * updated until a flash write. Reading from erased memory will
+         * signal a ECC error that is falsely corrected from 0xFF to 0xFD
+         * on the 16th byte of each 128-bit line.
+         *
+         * Workaround by setting the 16th byte of each line to 0xFF.
+         */
+
+        /* Get to the 16th byte of each line */
+        uint32_t addrOffset = (0xF - (address % 0x10));
+        uint8_t* buffer8 = buffer;
+
+        while(addrOffset < len) {
+            /* Check for the erased flash ECC correction */
+            if(buffer8[addrOffset] == 0xFD) {
+                buffer8[addrOffset] = 0xFF;
+            } else {
+                /* This could be an actual ECC error */
+                break;
+            }
+            /* Skip to the next 16th byte */
+            addrOffset += 0x10;
+        }
+    }
 }
 
 //******************************************************************************