[RFC v2] ARM: i.MX pllv1: Implement set_rate

[s.hauer@pengutronix.de (Sascha Hauer)]

On Sat, Jul 20, 2013 at 04:18:01PM +0400, Alexander Shiyan wrote:
> On Sat, 20 Jul 2013 13:58:29 +0200
> Sascha Hauer <s.hauer@pengutronix.de> wrote:
> 
> > > > On Sat, Jul 20, 2013 at 12:29:35PM +0400, Alexander Shiyan wrote:
> > > > > This patch implements frequency change for i.MX pllv1.
> > > > > Selection of the values of the registers is not optimal, since is
> > > > > made by simple enumeration of all possible values.
> > > > 
> > > > You do not mention why you want to adjust the rate. Normally we've been
> > > > happy with the static values from the bootloader.
> > > 
> > > For CPUfreq.
> > > Only one barrier to make it workable.
> > 
> > Isn't it better to adjust the dividers only? I haven't made good
> > experience with adjusting the PLLs.
> 
> The frequency value after booting can be quite arbitrary.
> 
> Since we define possible frequencies for the CPU (266 and 399 MHz),
> I can offer as variant to use a fixed constant values for PLL.

AFAIK the PLL should run at 800MHz. With dividers of 2, 3 and 6 we get
400, 266 and 133MHz. I don't think having more fine grained control
about the CPU frequency is necessary from a power saving point of view.
Let's keep the variants to a minimum to make the whole stuff more
robust.

Sascha

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