linux-kernel - Re: [PATCH 1/3] soundwire: qcom: drop unneeded DAI .set

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Date:   Fri, 3 Nov 2023 14:43:45 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Banajit Goswami <bgoswami@...cinc.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, linux-arm-msm@...r.kernel.org,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] soundwire: qcom: drop unneeded DAI .set_stream
 callback

On 25/10/2023 17:12, Pierre-Louis Bossart wrote:
> 
> 
> On 10/25/23 09:45, Krzysztof Kozlowski wrote:
>> Qualcomm Soundwire controller drivers do not support multi-link setups,
>> so DAI .set_stream() callback will not be used.  What's more, if called
>> it will overwrite the sdw_stream_runtime runtime set in DAI .startup
>> (qcom_swrm_startup()) causing issues (unsupported multi-link error) when
>> two Soundwire controllers are passed as codec DAIs.
> 
> This last sentence is confusing at best.
> 
> A controller can have one or more managers, each of whom can have one or
> more peripherals.
> 
> only peripherals should expose codec DAIs, managers should expose CPU DAIs.
> 
> Put differently, the controller is the host part while the peripheral is
> the codec part. "controllers passed as codec DAIs" is not really
> possible, or this was a typo?

No, it wasn't a typo. Take a look here:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts#n1023

The <&swr0 0> is the controller, although probably I should call it
manager, but in case of Qualcomm I think they are 1-to-1.

Best regards,
Krzysztof