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

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Message-ID: <a5dfaf2a-d2c8-468a-9bbe-38d11b1214a8@linaro.org>
Date: Tue, 7 Oct 2025 17:48:55 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 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 12:23, Konrad Dybcio wrote:
> 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?

Good question, it's not done for pre-audioreach. Let me investigate.

Neil

> 
> Konrad