linux-kernel - Re: [PATCH 07/11] soundwire: intel: Only call sdw stream APIs for the first cpu

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Message-ID: <5a7b75e5-4d64-9927-df81-68164ef2662a@linux.intel.com>
Date:   Wed, 26 Aug 2020 09:35:19 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Vinod Koul <vkoul@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        tiwai@...e.de, broonie@...nel.org, gregkh@...uxfoundation.org,
        jank@...ence.com, srinivas.kandagatla@...aro.org,
        rander.wang@...ux.intel.com, ranjani.sridharan@...ux.intel.com,
        hui.wang@...onical.com, sanyog.r.kale@...el.com,
        mengdong.lin@...el.com, bard.liao@...el.com
Subject: Re: [PATCH 07/11] soundwire: intel: Only call sdw stream APIs for the
 first cpu_dai

>> -	ret = sdw_prepare_stream(dma->stream);
>> +	/*
>> +	 * All cpu dais belong to a stream. To ensure sdw_prepare_stream
>> +	 * is called once per stream, we should call it only when
>> +	 * dai = first_cpu_dai.
>> +	 */
>> +	if (first_cpu_dai == dai)
>> +		ret = sdw_prepare_stream(dma->stream);
> 
> Hmmm why not use the one place which is unique in the card to call this,
> hint machine dais are only called once.

we are already calling directly sdw_startup_stream() and 
sdw_shutdown_stream() from the machine driver.

We could call sdw_stream_enable() in the dailink .trigger as well, since 
it only calls the stream API.

However for both .prepare() and .hw_free() there are a set of dai-level 
configurations using static functions defined only in intel.c, and I 
don't think we can move the code to the machine driver, or split the 
prepare/hw_free in two (dailink and dai operations).

I am not against your idea, I am not sure if it can be done.

Would you be ok to merge this as a first step and let us work on an 
optimization later (which would require ASoC/SoundWire synchronization)?