Hi,

On Wed, Jan 28, 2015 at 11:22:05PM +0100, Stefan Wahren wrote:

quoted

Mark Brown [off-list ref] hat am 27. Januar 2015 um 20:43 geschrieben:
On Tue, Jan 27, 2015 at 07:35:09PM +0100, Stefan Wahren wrote:

quoted

quoted

Mark Brown [off-list ref] hat am 27. Januar 2015 um 01:16
geschrieben:

quoted

quoted

quoted

okay i understand. But doesn't it need a extra driver to set the
switching
frequency because of the new compatible string?

quoted

quoted

I don't understand this bit at all, sorry.

quoted

Sebastian suggested a new sub-node in the devicetree:

quoted

powerpll {
compatible = "fsl,imx28-power-pll"
#clock-cells = <0>;
clock-frequency = <12345>;
}

quoted

and i think that the new compatible string needs a separate driver to take
care
of the switching frequency.

I can see that this has been suggested, what I can't understand is why
we would wish to do this but I am missing some context here which may
make it all perfectly clear.

The relevant register DC-DC Miscellaneous Register (HW_POWER_MISC) is described
in chapter 11.12.10 of the reference manual [1].

[1] - http://cache.freescale.com/files/dsp/doc/ref_manual/MCIMX28RM.pdf

Having a look at the datasheet my suggestion for the sub-node
doesn't make sense. I missunderstood how the hardware architecture
looks like, sorry for the noise :(

changing the switching frequency is not a common feature for this IC. In most
cases the clock for the DC-DC switching frequency runs at 24 MHz (ref_xtal).
Unfortunatelly this could cause interferences for example in UHF band. So
switching to ref_pll and changing clock divider is a option to avoid such
interferences without changing hardware.

I decided to implement it as a module parameter, because i see it's a
configuration option.

I think its best to use a DT property then. That way it can be set
appropiatly for boards known to use a band, which could have
interference problems.

So just add a simple property (without a subnode). If I understand
Mark correctly, there's a high chance more drivers will need to
describe the switching frequency, so I suggest to use a vendor
independent property name:

switching-frequency = <12345>;

-- Sebastian
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