"Read-only file system" error while writing]

[Gerhard Chvatal]

Hi!

Few months ago a had a similar problem.

gromit1463 at mailworks.org said:
> [...]
> I have a set of STMicro flash chips (M28W320CT) that use the Intel
> Extended CFI command set (0001) [...]

The M28W320CT is not really 100% compatible with the Intel Chips.
There is a small difference in the state machine:

 As stated in the data sheet of the INTEL 28F320C3 "APPENDIX A, 
 WSM CURRENT/NEXT STATES" on page 40, the device will present the status
 when in "Lock Oper. (Done) state" (usually after sending 60H followed
by
 D0h to the command interface).

 The M28W320CB _does_not_ present the status - it presents the array
data
 when read in this state.

Unfortunately, the Linux MTD Driver (Kernel 2.4.0-rmk2-bluemug1) 
assumes to have the status available after UNLOCK Operation.
(around line: 1365-1379 in cfi_cmdset_0001.c:do_unlock_oneblock()).

After 

  [...]
  cfi_write(map, CMD(0x60), adr);
  cfi_write(map, CMD(0x01), adr);
  chip->state = FL_UNLOCKING;
  [...]

do a

  cfi_write(map, CMD(0x70), cmd_addr);

to switch the state machine to READ_STATUS mode. Real Intel Chips will
ignore this.

I have never changed this, because we are still using INTEL chips in our
design, but if it works, it would be nice to have a feedback.

Gerhard
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