linux-kernel - Re: [PATCH v3 6/6] ASoC: qdsp6: dt-bindings: Add q6afe pcm dt binding documentation

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Message-ID: <b5c1328a-e3ca-826d-9ff0-f2bbce24ac22@linaro.org>
Date:   Wed, 12 Feb 2020 11:43:37 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Adam Serbinski <adam@...binski.com>
Cc:     Mark Brown <broonie@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Patrick Lai <plai@...eaurora.org>,
        Banajit Goswami <bgoswami@...eaurora.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 6/6] ASoC: qdsp6: dt-bindings: Add q6afe pcm dt binding
 documentation



On 12/02/2020 11:01, Adam Serbinski wrote:
>>>
>>> +
>>> + - qcom,pcm-slot-mapping
>>> +    Usage: required for pcm interface
>>
>> Are these not specific to 8k and 16k mode ?
>> We should probably list values for both modes here.
> 
> No, this is just the offset that the audio sample is placed in with 
> respect to a maximum of 4 slots, 16 bits wide, beginning with the sync 
> pulse.


That's not true atleast by the QDSP documentation,
according to it we will use more slots to transfer at higher sample 
rate. ex:
16 kHz data can be transferred using 8 kHz samples in two
slots.

Also there are 32 slots for each of 4 supported channels for PCM AFE port.


> 
> When switching between 8 and 16k sample rate, it is just the sync pulse 
> rate that is changed. The audio sample will be delivered in the same 
> slot, just at a different frequency.