[U-Boot] [PATCH] overo: add SPL support

[Wolfgang Denk]

Dear Andreas,

In message <201112201339.39460.schnitzeltony at gmx.de> you wrote:
>
> I don't know if I want to jump also into these changes now - especially since 
> I am quite new here..
> But for my intererst - since it seems more error tolerant: How is SDRAM timing 
> set up without exactly knowing what type is connected? Is there a good example 
> implementation in u-boot(-spl)?

In most cases thare is not an arbitrary range of RAM types, but only a
pretty small selection; even more often they differ only in size, not
in timings.  It depends on the set of possible configurations and
capabilities of the meory controller how to proceed then.  Typically
you will start with very conservative settings, and from the sizes
found you will know the correct configuration.

As for examples: probably not much in SPL, but a number of PPC board
use this. See for example "board/tqc/tqm8xx/tqm8xx.c" which probes
several banks of memory in 8, 9, and 10 column mode and then adjusts
timing, even taking into account that the CPU and bus clock (and thus
the refresh timings) are variable on some of these boards (you can set
the CPU clock through the "cpuclk" environment variable).

Best regards,

Wolfgang Denk

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