Messages in this thread | | | Subject | Re: [PATCH] sound: soc: fsl: Do not set DAI sysclk when it is equal to system freq | From | Łukasz Majewski <> | Date | Tue, 5 Sep 2017 23:13:40 +0200 |
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Hi Nicolin,
> 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?
This is how the simple-card (simple-sound-card) is written.
> >> 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@02100000/i2c@021a0000/tfa9879@6C > > This tfa9879 should be the CODEC right?
Yes. The tfa9879 is a codec (very simple -> I2S + I2C, mono).
They key point here is the asoc_simple_card_parse_clk() function from simple-card-utils.c
Please look how the clock is assigned; It first checks for cpu clock, then for "system-clock-frequency" DTS node and _finally_ looks for another "child" clock [1], which is the codec attached to I2C.
And from there it takes the 66 MHz CLK: /soc/aips-bus@02100000/i2c@021a0000/tfa9879@6C
> >> which has clock from I2C (66 MHz). > > You mean I2C scl or I2S sclk?
I2C scl.
> > ----------------------------------------------------------------- > > 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).
Please look into asoc_simple_card_parse_clk().
My DTS [1] (it is different than other in-tree supported codecs - at least I did not find similar setup in DTSes):
sound { compatible = "simple-audio-card"; label = "tfa9879-mono";
simple-audio-card,dai-link { /* DAC */ format = "i2s"; bitclock-master = <&dailink_master>; frame-master = <&dailink_master>;
dailink_master: cpu { sound-dai = <&ssi2>; }; codec { sound-dai = <&codec>; }; }; };
&i2c1 { clock-frequency = <400000>; pinctrl-names = "default"; pinctrl-0 = <&pinctrl_i2c1>; status = "okay";
codec: tfa9879@6C { #sound-dai-cells = <0>; compatible = "tfa9879"; reg = <0x6C>; }; };
&ssi2 { fsl,mode = "i2s-master"; status = "okay"; };
the ssi2 node is defined in imx6qdl.dtsi file (no changes).
The SOC is IMX6Q.
The TFA9879 is a slave for I2S transmission.
> >> [*] - 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. >
-- Best regards,
Lukasz Majewski
--
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