On Wednesday 04 July 2007, Sascha Hauer wrote:
I once wondered why it takes _so_ long to get a prompt on my MPC5200 board. The solution was simple: U-Boot was busy reading the environment from EEPROM several times.
Yes. That is one of the reasons, why it is strongly discouraged to use I2C EEPROM for environment storage.
I know it is, and it was the customers decision to so, but I think using an I2C eeprom _should_ be no problem. It's just like any other memory device.
ACK.
If no output on the serial console always means: "problem with memory", than this would be an easy indication for SDRAM problems. But I have seen lots of other errors, that lead to a hangup in the very early boot stage. Most of the time *before* SDRAM is initialized.
Don't have the boards where DIMMs can be changed some kind of beeper or LED telling you about memory problems?
Some have some don't.
Don't get me wrong. I generally like this 2 stage approach. For example it fits the NAND booting support (see nand_spl/*) where a small (4k on 4xx) first stage loader is needed. I'm just a little hesitant about dropping the full featured printf in early boot stages.
I think we have little choice if we want 4k boot block support, early console output _and_ a maintainable tree.
Yes. The current nand_spl implementation has no serial output at all. And when problems occurred (which has already happened and *not* in the SDRAM init process, just CPU setup which can be quite complicated and can not be deferred to after SDRAM init), I would have really liked this output. I once had a version with such a hardcoded serial output, but dropped it after everything was working. I should have kept it in the source via some "debug" functions.
Best regards, Stefan
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