[alsa-devel] [PATCH v5 1/2] ASoC: fsl: Add S/PDIF CPU DAI driver

[Sascha Hauer]

On Sat, Aug 17, 2013 at 02:56:11PM +0200, Tomasz Figa wrote:
> Hi Nicolin,
> > First, you are right that all the properties you just commented are
> > software configurations. And I got the point that device tree now
> > can't allow any software configuration even if the actual hardware
> > connection will depend on it.
> > 
> > If so, I would like to remove those abused clocks and also drop the
> > unused clocks in src<0-7>, then just remain those needed clocks src.
> > I think that can be plausible because there'll be no more clock abuse
> > and the driver will be able to get the source index from the name
> > 'src<num>'.
> 
> OK.
> 
> > And you are right about the 9 clock inputs, just there're not only 9
> > inputs but also an extra external clock from S/PDIF transmitter via
> > coaxial cable or optical fiber -- RxCLK. Please check the following
> > list:
> > 
> > 0000 if (DPLL Locked) SPDIF_RxClk else extal
> > 0001 if (DPLL Locked) SPDIF_RxClk else spdif_clk
> > 0010 if (DPLL Locked) SPDIF_RxClk else asrc_clk
> > 0011 if (DPLL Locked) SPDIF_RxClk else spdif_extclk
> > 0100 if (DPLL Locked) SPDIF_Rxclk else esai_hckt
> > 0101 extal_clk
> > 0110 spdif_clk
> > 0111 asrc_clk
> > 1000 spdif_extclk
> > 1001 esai_hckt
> > 1010 if (DPLL Locked) SPDIF_RxClk else mlb_clk
> > 1011 if (DPLL Locked) SPDIF_RxClk else mlb_phy_clk
> > 1100 mkb_clk
> > 1101 mlb_phy_clk
> 
> Could you explain what the above values are? If they are values written to 
> a 4-bit mux that selects RX clock source, then all the 16 clocks should be 
> specified from device tree, even if they are duplicated.

The S/PDIF core can recover the clock for the tx signal from the rx
signal. So if you have an S/PDIF input signal, then the DPLL will be
locked and the SPDIF_RxClk can be used for tx. So the above are really 8
clocks and one "If DPLL locked, use it" bit.

Sascha


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