linux-kernel - Re: [PATCH] soundwire: stream: only change state if needed

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Message-ID: <27a73cbd-9418-4488-5cb2-fb21f9fc9110@linux.intel.com>
Date:   Tue, 17 Mar 2020 07:22:47 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        alsa-devel@...a-project.org
Cc:     linux-kernel@...r.kernel.org, tiwai@...e.de, broonie@...nel.org,
        vkoul@...nel.org, gregkh@...uxfoundation.org, jank@...ence.com,
        slawomir.blauciak@...el.com,
        Bard liao <yung-chuan.liao@...ux.intel.com>,
        Rander Wang <rander.wang@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Hui Wang <hui.wang@...onical.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>
Subject: Re: [PATCH] soundwire: stream: only change state if needed

Hi Srinivas,

> This patch did not work for me as it is as wsa881x codec does prepare 
> and enable in one function, which breaks some of the assumptions in this 
> patch.

Ah yes, if two transitions happen in the same DAI callback that wouldn't 
work indeed. We should probably add this restriction to the state 
machine documentation, the suggested mapping from ASoC DAI states to 
stream states did not account for compound cases.

> However with below change I could get it working without moving stream 
> handling to machine driver.

The change below would be an error case for Intel, so it's probably 
better if we go with your suggestion. You have a very specific state 
handling due to your power amps and it's probably better to keep it 
platform-specific.

Can you confirm though that this patch works fine if you move all the 
stream transitions to the machine driver? That should be a no-op but 
better make sure there's no misunderstanding.

Thanks
-Pierre

> ---------------------------->cut<-------------------------------
> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> index be71af4671a4..4a94ea64c1c5 100644
> --- a/drivers/soundwire/stream.c
> +++ b/drivers/soundwire/stream.c
> @@ -1574,7 +1574,8 @@ int sdw_prepare_stream(struct sdw_stream_runtime 
> *stream)
> 
>          sdw_acquire_bus_lock(stream);
> 
> -       if (stream->state == SDW_STREAM_PREPARED) {
> +       if (stream->state == SDW_STREAM_PREPARED ||
> +           stream->state == SDW_STREAM_ENABLED) {
>                  /* nothing to do */
>                  ret = 0;
>                  goto state_err;
> @@ -1754,7 +1755,8 @@ int sdw_disable_stream(struct sdw_stream_runtime 
> *stream)
> 
>          sdw_acquire_bus_lock(stream);
> 
> -       if (stream->state == SDW_STREAM_DISABLED) {
> +       if (stream->state == SDW_STREAM_DISABLED ||
> +           stream->state == SDW_STREAM_DEPREPARED) {
>                  /* nothing to do */
>                  ret = 0;
>                  goto state_err;
> ---------------------------->cut<-------------------------------
> 
> --srini
> 
>> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
>> index 1b43d03c79ea..3319121cd706 100644
>> --- a/drivers/soundwire/stream.c
>> +++ b/drivers/soundwire/stream.c
>> @@ -1572,6 +1572,7 @@ int sdw_prepare_stream(struct sdw_stream_runtime 
>> *stream)
>>       sdw_acquire_bus_lock(stream);
>>       if (stream->state == SDW_STREAM_PREPARED) {
>> +        /* nothing to do */
>>           ret = 0;
>>           goto state_err;
>>       }
>> @@ -1661,6 +1662,12 @@ int sdw_enable_stream(struct sdw_stream_runtime 
>> *stream)
>>       sdw_acquire_bus_lock(stream);
>> +    if (stream->state == SDW_STREAM_ENABLED) {
>> +        /* nothing to do */
>> +        ret = 0;
>> +        goto state_err;
>> +    }
>> +
>>       if (stream->state != SDW_STREAM_PREPARED &&
>>           stream->state != SDW_STREAM_DISABLED) {
>>           pr_err("%s: %s: inconsistent state state %d\n",
>> @@ -1744,6 +1751,12 @@ int sdw_disable_stream(struct 
>> sdw_stream_runtime *stream)
>>       sdw_acquire_bus_lock(stream);
>> +    if (stream->state == SDW_STREAM_DISABLED) {
>> +        /* nothing to do */
>> +        ret = 0;
>> +        goto state_err;
>> +    }
>> +
>>       if (stream->state != SDW_STREAM_ENABLED) {
>>           pr_err("%s: %s: inconsistent state state %d\n",
>>                  __func__, stream->name, stream->state);
>> @@ -1809,6 +1822,12 @@ int sdw_deprepare_stream(struct 
>> sdw_stream_runtime *stream)
>>       sdw_acquire_bus_lock(stream);
>> +    if (stream->state == SDW_STREAM_DEPREPARED) {
>> +        /* nothing to do */
>> +        ret = 0;
>> +        goto state_err;
>> +    }
>> +
>>       if (stream->state != SDW_STREAM_PREPARED &&
>>           stream->state != SDW_STREAM_DISABLED) {
>>           pr_err("%s: %s: inconsistent state state %d\n",
>>