iMX27 clock settings

[Sascha Hauer]

On Tue, Feb 14, 2012 at 04:10:08PM +0100, Igor Trevisan wrote:
> Hi,
> 
> I'm working on a custom board based on iMX27L. Initially I worked with Redboot
> as Linux bootloader but now, I'm happily working with Barebox (2012.01.0)
> having replaced Redboot with it.
> 
> Everithing is fine (thanks to the guys in the list for helping me!) but...
> I noticed that my Linux apps run more slowly within my system if it's
> started by Barebox
> then if it's started by Redbbot.
> I think it's a matter of internal clocks settings.
> 
> I see that Redboot, for example, set:
>         CSR=0x33F38107
> while Barebox does:
> 	writel(0x33F30307 | CSCR_MPLL_RESTART | CSCR_SPLL_RESTART, CSCR)
> That brings to CSR=0x33F30307 at the end of the PLLs restart procedure.
> 
> Reading the Manual I can see that the differences between the two settings
> mean having an arm_clk that is 2/3 and an AHB_clk that's the half.
> 
> Is there a particular reason for having these "slower configuration"?

One thing that might be interesting in such cases is the output of
the dump_clocks command.

Sascha


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