iMX27 clock settings

[Kamel BOUHARA]

Hi Igor,

What revision of imx27 silicon do you have?
If it's a rev2.0 or 2.1, you shoult take a look a the freescale errata in
order to set your PLL properly.

Regards.

2012/2/14 Igor Trevisan <igt1972 at gmail.com>

> 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"?
>
> I tried to change the lowlevel_init.S to force 0x33F38107 into CSCR
> at startup but, after that change, my board starts, has time to write
> somenthing on the
> serial console:
>
> "barebox 2012.01.0-svn11070-dirty1 (Feb 14 2012 - 11:10:39)
>
> Board: Freescale iÿ"
>
> and then restarts... continuously.
>
> Can anybody help me to understand this and to make (if possible) my
> system faster?
> Thanks in advance,
> Igor
>
>
> --
> "Don't find fault, find a remedy."
> (Henry Ford)
>
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> barebox at lists.infradead.org
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>



-- 

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*Kamel BOUHARA*
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