Dear Thomas,
in message D9F0B2AD4531B0449D51C1F09199D484050E72@mail.kom-saarbruecken.com you wrote:
Yes, I know that this has been discussed recently and the recommendation is to store the environment in flash, but:
Indeed.
- storing the environment in flash with redundancy means to spend 2 (128
kB in our case) sectors for approx. 1 kB of environment data.
As long as you say "spend" (and not "waste") that's ok :-)
- the problem described for EEPROM storage should also appear when
storing other data in EEPROM's (e.g. SPD data etc.) and thus a proper
Indeed. It happened before.
solution should be found for EEPROM storage.
Yes, machine should work, men should think, etc. In the meantime we have to live with the current situation. The question is how reliable your system has to be.
Note that even with perfect operation of the EEPROM you still cannot get the robustness you get with redundand flash sectors. Not unless you have two EEPROM chips on your board for redundant storage, but I haven't seen this yet. And it would be painfully slow to boot, too.
- The solution provided in common/soft_i2c.c sets the SDA line to 1 and
issues 9 cycles on the SCL line. Is this an undefined I2C pattern
No, it's not undefined. It's well-defined as you just described.
causing a reset on the I2C bus (which is not specified in the I2C specification)? Why is it not sufficient to issue a simple Start/Stop sequence on the bus?
Because the I2C controller may be in a state where it misinterprets this; see "doc/I2C_Edge_Conditions".
- Are there conditions known to cause similar effects with flash chips
as described for EEPROM devices? Could power loss or similar conditions
No.
when writing environment sectors cause a flash device to destroy other sectors than the just written one?
In theory yes. You could assume a system without power monitoring where the power is failing slowly so that at some point during the brownout the CPU migth start executing bogus insructions, or that some bus driver corrupts the addresses or data, or... In theory anything can happen.
Best regards,
Wolfgang Denk