linux-kernel - Re: [PATCH RFC 3/6] ASoC: soc: qcom: sc8280xp: add support for I2S clocks

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Message-ID: <f15ea346-43f7-49bc-bd5e-47510a48892d@oss.qualcomm.com>
Date: Tue, 7 Oct 2025 12:23:50 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Neil Armstrong <neil.armstrong@...aro.org>,
        Srinivas Kandagatla <srini@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
Cc: linux-sound@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH RFC 3/6] ASoC: soc: qcom: sc8280xp: add support for I2S
 clocks

On 10/7/25 9:02 AM, Neil Armstrong wrote:
> On 10/7/25 00:21, Srinivas Kandagatla wrote:
>>
>>
>> On 10/6/25 7:37 PM, Neil Armstrong wrote:
>>> Add support for getting the I2S clocks used for the MI2S
>>> interfaces, and enable/disable the clocks on the PCM
>>> startup and shutdown card callbacks.
>>>
>>> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
>>> ---

[...]

>>> +static int sc8280xp_snd_startup(struct snd_pcm_substream *substream)
>>> +{
>>> +    unsigned int codec_dai_fmt = SND_SOC_DAIFMT_BC_FC | SND_SOC_DAIFMT_NB_NF | SND_SOC_DAIFMT_I2S;
>>> +    struct snd_soc_pcm_runtime *rtd = substream->private_data;
>>> +    struct sc8280xp_snd_data *pdata = snd_soc_card_get_drvdata(rtd->card);
>>> +    struct snd_soc_dai *cpu_dai = snd_soc_rtd_to_cpu(rtd, 0);
>>> +    struct snd_soc_dai *codec_dai = snd_soc_rtd_to_codec(rtd, 0);
>>> +    int index;
>>> +
>>> +    switch (cpu_dai->id) {
>>> +    case PRIMARY_MI2S_RX...QUATERNARY_MI2S_TX:
>>> +    case QUINARY_MI2S_RX...QUINARY_MI2S_TX:
>>> +        index = sc8280xp_snd_i2s_index(cpu_dai);
>>
>> What is the mclk and bitclk rate set here, we can not rely on the
>> default rate.
> 
> The default rates are set in DT:
> +        assigned-clocks = <&q6prmcc LPASS_CLK_ID_PRI_MI2S_IBIT LPASS_CLK_ATTRIBUTE_COUPLE_NO>,
> +                  <&q6prmcc LPASS_CLK_ID_MCLK_1 LPASS_CLK_ATTRIBUTE_COUPLE_NO>;
> +        assigned-clock-rates = <1536000>,
> +                       <24576000>;

Is there a way to infer these rates based on the DT audio
connection graph?

Konrad