linux-kernel - Re: [PATCH 2/2] ASoC: qcom: Move Soundwire runtime stream alloc to soundcards

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Date:   Tue, 28 Nov 2023 11:49:44 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     linux-arm-msm@...r.kernel.org, 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>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, linux-sound@...r.kernel.org
Subject: Re: [PATCH 2/2] ASoC: qcom: Move Soundwire runtime stream alloc to
 soundcards



On 11/28/23 10:59, Krzysztof Kozlowski wrote:
> On 28/11/2023 17:56, Krzysztof Kozlowski wrote:
>> Currently the Qualcomm Soundwire controller in its DAI startup op
>> allocates the Soundwire stream runtime.  This works fine for existing
>> designs, but has limitations for stream runtimes with multiple
>> controllers, like upcoming Qualcomm X1E80100 SoC with four WSA8840
>> speakers on two Soundwire controllers.
>>
>> When two Soundwire controllers are added to sound card codecs, Soundwire
>> startup() is called twice, one for each Soundwire controller, and second
>> execution overwrites what was set before.  During shutdown() this causes
>> double free.
>>
>> It is expected to have only one Soundwire stream runtime, thus it should
>> be allocated from SoC soundcard context startup(), not from each
>> Soundwire startup().  Such way will properly handle both cases: one and
>> two Soundwire controllers in the stream runtime.
>>
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>>
>> ---
>>
>> This is an entirely different approach than my previous try here:
>> https://lore.kernel.org/all/20231025144601.268645-1-krzysztof.kozlowski@linaro.org/
> 
> ... and I forgot to thank you Pierre-Louis for patient explanation of
> the case in my previous try. Your review was much appreciated!

You're welcome. It's good if we have multiple platforms using the
'stream' concept in similar ways.