mvebu: tclk detection for armada-xp and marvell packet processor with integrated CPU
andrew at lunn.ch
Mon Nov 17 06:18:39 PST 2014
On Mon, Nov 17, 2014 at 09:34:37AM +0100, Thomas Petazzoni wrote:
> Dear Chris Packham,
> On Mon, 17 Nov 2014 02:12:51 +0000, Chris Packham wrote:
> > One of the first problems I encountered looking at the Marvell Packet
> > Processor with integrated CPU (I'll refer to that as 'the PP' throughout
> > the rest of this email) was that it has a different TCLK to the armada-xp.
> > It appears that for both the PP and the armada-xp the TCLK is hard-coded
> > (to 200MHz and 250MHz respectively) and cannot be detected as far as I
> > can see from the various data-sheets. I was hoping to re-use
> > drivers/clk/mvebu/armada-xp.c but I need to figure out how to make
> > axp_get_tclk_freq() give me an appropriate answer depending on the SoC.
> > If this were in the mach-mvebu code I could just use mvebu_get_soc_id()
> > to fetch the device id. Is there an equivalent I could use in generic code?
> > One option would be to use a different compatible string in the dts.
> > That would also give me a way of handling other differences (the
> > clock-gating is a subset of what's available on the armada-xp). How
> > different would things have to be before it's worth spinning the PP code
> > out into a file of it's own?
> To me, it indeed seems like you need a different compatible string
> here. Whether a separate file from drivers/clk/mvebu/armada-xp.c is
> needed or not will depend on whether only the tclk frequency differs,
> or whether also the ratios with other clocks differ.
I agree here about the compatibility string. The Kirkwood PP also has
a different compat string for some drivers and an .dtsi file.
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