C3 NOR flash /dev/mtd0 write only?

[Cam Mayor]

Hi all,

I've been pounding on this problem for a while, but the answer has so far 
eluded me.  My /dev/mtd0 (NOR flash) that should be rw is acting as ro.

I am using intel C3 NOR flash (two parallel 32Mbit x 16-B) on a guide A07 
(cs89712 processor, similar to the cdb89712 demo board).  It's been working 
fine for a couple of years, but now we want to do some direct writing of the 
flash from user space. (ie.  cat file > /dev/mtd0)

I can accurately read the contents of the flash with 'cat /dev/mtd0 > file' 
and 'cat /dev/mtdr0 > file'.  /dev/mtd0 is supposed to be rw, but when i do 
cat file > /dev/mtd0, the error i get is:
cat: write: Read-only file system  

I cannot find the reason this is happening.  I believe it is getting marked 
as read only somewhere in the kernel/driver, but i'm not sure where.  If you 
have any ideas, please pass them along.  Here's some system data:

# cat /proc/mtd
dev:    size   er  name
mtd0: 00800000 00020000 "flash"
mtd1: 0000c000 00000010 "SRAM"
mtd2: 00000080 00010000 "BootROM"
mtd3: 00800000 00020000 "Physically mapped flash"
mtd4: 09000000 00004000 "guidenand"

(the following was the output when i enabled DEBUG_CFI_FEATURES in the driver)
  Feature/Command Support: 0066
     - Chip Erase:         unsupported
     - Suspend Erase:      supported
     - Suspend Program:    supported
     - Legacy Lock/Unlock: unsupported
     - Queued Erase:       unsupported
     - Instant block lock: supported
     - Protection Bits:    supported
     - Page-mode read:     unsupported
     - Synchronous read:   unsupported
  Supported functions after Suspend: 01
     - Program after Erase Suspend: supported
  Block Status Register Mask: 0003
     - Lock Bit Active:      yes
     - Valid Bit Active:     yes
  Vcc Logic Supply Optimum Program/Erase Voltage: 0.3 V
  Vpp Programming Supply Optimum Program/Erase Voltage: 12.0 V

when using the 'erase' command that comes in mtd/utils/erase.c, it provided 
the following output:
# ./erase /dev/mtd0
Erase Total 1 Units
Region 0 is at 0 of 8 sector and with sector size 4000
Region 1 is at 131072 of 63 sector and with sector size 20000
Performing Flash Erase of length 16384 at offset 0x0
MTD Erase failue: Read-only file system

Some of my debug code in the driver to tell me what's what says that the 
flash says the following two flags are defined:
MTD_CLEAR_BITS defined
MTD_ERASEABLE defined
and that the erase, unlock, and write functions exist (they have fcn pointer 
locations, not just NULL)

my relevant /dev entries are as follows:
# ll /dev/mtd*
crw-------    1 root     root      90,   0 Aug 26 21:57 /dev/mtd0
crw-------    1 root     root      90,   2 Aug 26 21:57 /dev/mtd1
crw-------    1 root     root      90,   4 Aug 26 21:57 /dev/mtd2
crw-------    1 root     root      90,   6 Aug 26 21:57 /dev/mtd3
crw-------    1 root     root      90,   8 Aug 26 21:57 /dev/mtd4
brw-------    1 root     root      31,   0 Aug 26 21:57 /dev/mtdblock0
brw-------    1 root     root      31,   1 Aug 26 21:57 /dev/mtdblock1
brw-------    1 root     root      31,   2 Aug 26 21:57 /dev/mtdblock2
brw-------    1 root     root      31,   3 Aug 26 21:57 /dev/mtdblock3
crw-------    1 root     root      90,   1 Aug 26 21:57 /dev/mtdr0
crw-------    1 root     root      90,   3 Aug 26 21:57 /dev/mtdr1
crw-------    1 root     root      90,   5 Aug 26 21:57 /dev/mtdr2
crw-------    1 root     root      90,   7 Aug 26 21:57 /dev/mtdr3
crw-------    1 root     root      90,   9 Aug 26 21:57 /dev/mtdr4

I am using linux 2.4.19-rmk7 with an MTD version that i can't confirm the 
exact date (another developer downloaded an arbitrary version from the mtd 
cvs and added it to ours) ...it is approximately from 2003/03/26.

thanks in advance for any tips/help.

cheers,
cam

-- 
Cameron Mayor
Iders Incorporated
600A Clifton Street
Winnipeg, MB Canada R3G 2X6
http://www.iders.ca