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

> On Wed, Sep 06, 2017 at 11:22:48AM +0200, Łukasz Majewski wrote:
>
>>> Here is the routine that I understood from the code:
>>> 1) asoc_simple_card_parse_clk_cpu(dev, cpu, dai_link, cpu_dai);
>>> => asoc_simple_card_parse_clk(dev, cpu, // cpu node in sound{} [1]
>>> dai_link->cpu_of_node, // node ssi2 [2]
>>> cpu_dai, dai_link->cpu_dai_name);
>>> ==> 1.1) devm_get_clk_from_child(dev, node, NULL); // [1]
>>> ==> 1.2) of_property_read_u32(node, "system-clock-frequency", &val)// [1]
>>> ==> 1.3) devm_get_clk_from_child(dev, dai_of_node, NULL); // [2]
>
>>> For the cpu routine, it first checks for clock property under cpu
>>> node of simple-card, then for "system-clock-frequency" in the cpu
>>> node of simple-card, and finally looks for clock property in ssi2
>>> node.
>
>> -----> dev: sound
>> -----> clk node: /soc/aips-bus@02000000/spba-bus@02000000/ssi@0202c000
>> -----> Clk asignment
>>
>> And this clock is taken from this node. It looks like ipg clock for ssi...
>
> This makes sense now. The devm_get_clk_from_child() in 1.3) fetched
> the first clock of ssi2 -- ipg clock.

Yes, exactly (for SSI2) [1]:

clocks = <&clks IMX6QDL_CLK_SSI2_IPG>,
<&clks IMX6QDL_CLK_SSI2>;
clock-names = "ipg", "baud";


>
>> The problem is with the "lack" of clock nodes/properties at
>>
>> dailink_master: cpu {
>> sound-dai = <&ssi2>;
>> clock = <&SSSS>;

If possible I do prefer a solution, which uses only DTS.

Side question - how to refer to baud clock from [1]?


>> system-clock-frequency = <XXXX>;
>> };
>
> This is the right solution based on current simple-card driver. For
> SSI (having two clocks), you have to specify the baud clock in the
> cpu node like that. I believe this is what the simple-card designer
> expected users to do since the cpu node is the first place that the
> driver tries to look at.

I will give a shoot the option with adding the ipg clock.

>
>> I think that the proper solution would be to add check for:
>>
>> freq < sysclk/5 in fsl_ssi_set_dai_sysclk() and return -ENOTSUPP to
>> make the simple-audo-card driver happy (and not introducing
>> regressions).
>
> As I said in the first place, adding another check in set_sysclk()
> is not that essential but seems to be plausible to me. So I am okay
> if you really want to have that.
>

Thanks for help.

--
Best regards,

Lukasz Majewski

--

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