[PATCH] sound: soc: fsl: Do not set DAI sysclk when it is equal to system freq

[Nicolin Chen]

On Tue, Sep 05, 2017 at 10:35:34AM +0200, Łukasz Majewski wrote:

> >And apparently, we shouldn't set bitclk to 66MHz either. Can
> >you help to find where this 66MHz comes from?

> 2. int asoc_simple_card_init_dai() @ simple-card-utils.c

Oh, I just searched in the simple-card.c but missed this file.

> In this function (point 2.) the
> simple_dai->sysclk is set and:
> snd_soc_dai_set_sysclk(dai, 0, simple_dai->sysclk, 0)
> which sets frequency to 66 MHz [*].
> 
> The asoc_simple_card_init_dai() is called in
> asoc_simple_card_dai_init() @ simple-card.c
> which is assigned to dai_link->init
> dai_link->init		= asoc_simple_card_dai_init; @ simple_card.c
> 
> And the sysclk itself is defined at:
> -------------------------------------
> dai_props->codec_dai->sysclk, which is used at:a

Why codec_dai? Why not dai_props->cpu_dai->sysclk since we are talking
about SSI?

> asoc_simple_card_startup(), asoc_simple_card_shutdown() and others
> functions at simple-card.c
> It is setup at:
> asoc_simple_card_parse_clk() @ simple-card-utils.c from macro:
> #define asoc_simple_card_parse_clk_cpu()
> And the problem is:
> -------------------
> 
> At the
> asoc_simple_card_parse_clk()
> we finally go to dts node:
> /soc/aips-bus at 02100000/i2c at 021a0000/tfa9879 at 6C

This tfa9879 should be the CODEC right?

> which has clock from I2C (66 MHz).

You mean I2C scl or I2S sclk?

-----------------------------------------------------------------

But anyway, I feel very confused here as you have 66MHz clock rate
(regardless of it purpose) for a codec dai but it's been passed to
a cpu dai (SSI).

> [*] - I could workaround this problem by setting:
> 
> system-clock-frequency = <0> in
> 
> 			dailink_master: cpu {
> 			    sound-dai = <&ssi2>;
> 			};
> 
> but this is IMHO even worse hack.... than this patch.

I haven't used simple-card for a while so I forgot how to define
its DT bindings specifically. But you should assign ssi2 as the
CPU dai and assign tfa9879 as a CODEC dai.