Re: [PATCH v2 0/7] Renesas R8A7790 Common Clock Framework support

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Magnus,

On Thursday 14 November 2013 19:16:05 Magnus Damm wrote:
> Hi Laurent,
> 
> Thanks for V2, it is looking better and better. Great that r8a7791 and
> r8a7790 can share the CPG code. I have now finally got my r8a7791 board
> replaced so I intend to try your code out on Lager and then see if I can
> cook something up on Koelsch.

I was actually planning to test the code on the Koelsch board. I don't want to 
step on anyone's toes, so please let me know if someone is already working on 
CCF patches for M2, otherwise I'll send them.

> I have one question related to the CPG. What is your plan regarding CPU
> Frequency scaling? I'd like to see "z_clk" and "z2_clk" implemented together
> with some way to let CPUFreq scale "z_clk". Can you please spend some time
> on that?

Z2 is a fixed factor clock, I'll just add it to DT.

Z is a bit more tricky. It's the output of a pure multiplier (PLL0) followed 
by a pure divisor (SYS-CPU divider 1). I can easily model the two as separate 
clock devices, but I'm unsure about what should be done at runtime when 
setting the Z clock frequency. Would it be enough to have a fixed PLL0 
frequency and configure the SYS-CPU divider 1 only (from 1/1 to 1/32), or 
would we need to configure the PLL0 multiplier as well for a more fine-grained 
Z frequency configuration ?

-- 
Regards,

Laurent Pinchart