[U-Boot-Users] CFI conformant flash: REDUX

[joseph_sacco at comcast.net]

In a recent post I described a problem getting the common CFI flash driver in 
u-boot-1.2.0  to work with a pair of Spansion S29JL064H memory devices connected 
on parallel. After plodding through the CFI flash driver source code and 
conducting some experiments, the root cause of the problem was found to be an 
Endian problem.  The flash on this particular board is wired  little Endian. The 
processor on the board, an MPC8270, is big Endian.

The CFI flash driver source, drivers/cfi_flash.c, supports little ENDIAN when a 
preprocessor macro, __LITTLE_ENDIAN, is defined.  As quick an dirty hack I 
uncommented  the CFLAGS line in the drivers Makefile to enable debugging and 
added '-D__LITTLE_ENDIAN' to the CFLAGS list. This hack actually worked:

     [from flinfo]
     Bank # 1: CFI conformant FLASH (32 x 16)  Size: 16 MB in 142 Sectors
        AMD Standard command set, Manufacturer ID: 0x01, Device ID: 0x7E0201
        Erase timeout: 8192 ms, write timeout: 1 ms

The driver makefile hack far is too encompassing, which leads to a question: 

     "Where is the right place to define this preprocessor macro definition?"

The board configuration header file is the obvious place.  However,  defining 
__LITTLE_ENDIAN in a  the board configuration header file for a board with a big 
ENDIAN processor causes all sorts of michief.   Changing the name of the 
__LITTLE_ENDIAN macro in drivers/cfi_flash.c to something less generic would 
also be a bad idea.

The following might be a workable approach.  I have validated that it works on 
this particular board.

* in the board configuration header file

#define CFG_FLASH_LITTLE_ENDIAN

* in drivers/cfi_flash.c

--- u-boot-1.2.0/drivers/cfi_flash.c.orig       2007-10-26 14:36:00.060179333 
-0400
+++ u-boot-1.2.0/drivers/cfi_flash.c    2007-10-26 15:18:01.485629019 -0400
@@ -56,6 +56,10 @@
  *
  */

+#ifdef CFG_FLASH_LITTLE_ENDIAN
+#define __LITTLE_ENDIAN
+#endif
+
 #ifndef CFG_FLASH_BANKS_LIST
 #define CFG_FLASH_BANKS_LIST { CFG_FLASH_BASE }
 #endif


Thoughts?

-Joseph

--
joseph_sacco [at] comcast [dot] net