Re: [RFC 1/6] video: hdmi: add helper function for N and CTS

[Mark Brown <broonie@kernel.org>]

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On Tue, Jan 19, 2016 at 04:54:30PM +0000, Russell King - ARM Linux wrote:
> On Tue, Jan 19, 2016 at 02:40:31PM +0100, Arnaud Pouliquen wrote:
> > From: Moise Gergaud <moise.gergaud@st.com>

> > Add helper function to compute HDMI CTS and N parameters
> > Implementation is based on HDMI 1.4b specification.

> You should note that these CTS/N parameters are for where the audio and
> video clocks are coherent: iow, they are derived from the same source.
> If they can drift (because they're generated from different sources)
> then a hardware implementation which automatically calculates CTS is
> needed.

> However, some of the values given in the HDMI specs for CTS are actually
> two values, because a single value does not specify the audio clock even
> with the N values given.  For these, the values returned will not give
> an accurate clock - this should also be noted.

> Next, does "pixel clock" make sense when you have pixel repetition?
> Would calling this "tdms_clock" be more accurate to the specification
> and less mis-leading to users?

It'd also be good to capture some of the above information from Russell
in the code so other people don't miss it when using the helpers.

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