MQX TWRMCF54418 Boot Loader Bug

[dwarkentin]

The NAND FLASH boot loader code in the TWRMCF54418 bsp has a bug that prevents bit errors from being corrected when firmware images are transferred from FLASH to RAM.

In the file mqx/source/bsp/twrmcf54418/bootstrap.c the page transfers are configured for 2kb plus the full spare data length (2kb + 64 bytes) but this overloads the ECC engine and causes it to always report 32-bit errors and prevents it from correcting actual bit errors. The correct transfer length is 2kb + 60 bytes which includes the exact number of ECC bytes and no extra bytes.

nfc_ptr->SECSZ = BSP_PHYSICAL_PAGE_SIZE + NANDFLASH_SPARE_AREA_SIZE;

needs to be changed to

nfc_ptr->SECSZ = BSP_PHYSICAL_PAGE_SIZE + 60;

I've checked MQX 4.0 to 4.2 and all versions were affected.

[dwarkentin · Accepted solution]

I was mistaken about the exact cause of the ECC engine failure. The actual cause was the even number being written to the SECSZ register. The MCF54418 TWR board uses 16-bit NAND FLASH memory and the NFC in the MCF54418 requires an odd number in the SECZ register for 16-bit devices. See section 22.3.13 in the MCF54418 Reference Manual.

The corrected line of code is:

nfc_ptr->SECSZ = NANDFLASH_PHYSICAL_PAGE_SIZE + NANDFLASH_SPARE_AREA_SIZE + 1;

and here is the entire bootstrap_sram_read_data function including the ECC engine result.

/*FUNCTION*-------------------------------------------------------------------
*
* Function Name : bootstrap_sram_read_data
* Returned Value : void
* Comments : Read data from the NAND Flash memory. Block# and page#
* must be specified.
* This code must be linked to Internal SRAM memory.
*
*END*----------------------------------------------------------------------*/
__declspec(bootstrap_sram_code)
static void bootstrap_sram_read_data(uint32_t block,uint32_t page)
{
 NFC_MemMapPtr nfc_ptr;
 uint32_t i;

/* Get the pointer to nfc registers structure */
 nfc_ptr = (&((VMCF5441_STRUCT_PTR)_PSP_GET_IPSBAR())->NFC);

/* Clearing interrupts bits */
 nfc_ptr->ISR |= (NFC_ISR_DONECLR_MASK |
 NFC_ISR_DONEEN_MASK |
 NFC_ISR_IDLECLR_MASK |
 NFC_ISR_IDLEEN_MASK);

/* Clearing buf in use */
 //for(i=0;i<NANDFLASH_PHYSICAL_PAGE_SIZE;i++)
 // NFC_SRAM_B0_REG(nfc_ptr, i) = 0;


 /* setting ROW and COLUMN address */
 page &= 0x3F;
 block &= 0x7FF;
 nfc_ptr->RAR = 0x11000000 + page + (block<<6);
 nfc_ptr->CAR = 0x00000000;

nfc_ptr->CMD1 = NFC_CMD1_BYTE2(NANDFLASH_CMD_PAGE_READ_CYCLE2);
 nfc_ptr->CMD2 = NFC_CMD2_BYTE1(NANDFLASH_CMD_PAGE_READ_CYCLE1) |
 NFC_CMD2_CODE(0x7EE0) |
 NFC_CMD2_BUFNO(0);

/* configuring Sector size */
 nfc_ptr->SECSZ = NANDFLASH_PHYSICAL_PAGE_SIZE + NANDFLASH_SPARE_AREA_SIZE + 1;

/* 32bit ECC, 16bit data bus, 1 page cnt */
 nfc_ptr->CFG = ( NFC_CFG_ECCAD((BSP_PHYSICAL_PAGE_SIZE + NANDFLASH_SPARE_AREA_SIZE)>>3) |
 NFC_CFG_ECCSRAM_MASK |
 NFC_CFG_ECCMODE(7) |
 NFC_CFG_IDCNT(5) |
 NFC_CFG_TIMEOUT(6) |
 NFC_CFG_BITWIDTH_MASK |
 NFC_CFG_PAGECNT(1));

/* Sending START */
 nfc_ptr->CMD2 |= NFC_CMD2_BUSY_START_MASK;

/* Polling for cmd done IRQ*/
 while(!(nfc_ptr->ISR & NFC_ISR_IDLE_MASK))
 {
 }

 _bit_error_count = NFC_SRAM_B0_REG( nfc_ptr, BSP_PHYSICAL_PAGE_SIZE + NANDFLASH_SPARE_AREA_SIZE + 7);

}

_bit_error_count is a global variable instead of a return value which was necessary to reduce code size due to the very limited amount of boot code memory.

[miduo]

Hi,

Yes, we had awared this already. We have examined and compared the sources of the BSP driver and the NFC driver included in the FFS/MFS-driver. There are several differences between the two, most of it due to the FFS/MFS-driver also reading some meta-data with every read. The two drivers appear to use different definitions of the ECC status word. It therefore seem to us that we are missing some information.