[U-Boot] [PATCH] fsl: verify writes to the MAC address EEPROM

[Timur Tabi <timur@freescale.com>]

Wolfgang Denk wrote:
> And the setting cannot be read back through some GPIO pin eitheer?

Technically, the FPGA (on ngPIXIS boards, of which there are only a few)
reads all of the switches and allows software to set and read the values.
But I've found it to be unreliable.  For example, on one board, SW7 is set
to 00001101, but the ngPIXIS shows 00000000.

And even if it were reliable, it wouldn't help, because the ngPIXIS reads
the software-programmable settings only on boot time.  So in order for me to
override the dip switch, I would need to program the right value and then
reboot the board.

And that assumes that the board doesn't have a broken FPGA firmware.  I
believe the current version is 11, or maybe 13.  The version on my board is 4.

The majority of our boards that use this EEPROM don't have an ngPIXIS, they
have the old-style PIXIS, which definitely does not allow software to
read/set any dip switches.

And this isn't the worst part of our designs.  On the P1022, for example,
the same pins are used for the DVI signals and the local bus (used for NOR
flash), so it's not possible to use flash memory while the video display is
active.   That means we can't turn on the video until after relocation, and
when we do, we lose the ability to update flash.