[alsa-devel] [PATCH] ASoC: dapm: Don't check dummy dai in soc_dapm_dai_stream_event

[Lars-Peter Clausen]

On 06/17/2015 05:41 AM, Shengjiu Wang wrote:
> Dummy dai can be used by multiple sound card. But it only belong to one
> card's dapm list. If another card use it, there will be dapm_assert_locked
> warning.
>
> [   20.015782] WARNING: CPU: 1 PID: 661 at sound/soc/soc-dapm.c:124 dapm_assert_locked.isra.36+0x4c/0x58()
> [   20.025249] Modules linked in:
> [   20.028349] CPU: 1 PID: 661 Comm: aplay Not tainted 4.1.0-rc6-next-20150605-00004-gaee05d8-dirty #92
> [   20.037528] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
> [   20.044110] Backtrace:
> [   20.046614] [<80012e00>] (dump_backtrace) from [<80012fa0>] (show_stack+0x18/0x1c)
> [   20.054229]  r6:809e8060 r5:00000000 r4:00000000 r3:00000000
> [   20.060002] [<80012f88>] (show_stack) from [<807a0f74>] (dump_stack+0x80/0x9c)
> [   20.067293] [<807a0ef4>] (dump_stack) from [<8002b144>] (warn_slowpath_common+0x7c/0xb4)
> [   20.075427]  r5:0000007c r4:00000000
> [   20.079065] [<8002b0c8>] (warn_slowpath_common) from [<8002b1a0>] (warn_slowpath_null+0x24/0x2c)
> [   20.087898]  r8:00000001 r7:88007c28 r6:ed94a680 r5:809e83e4 r4:ed83d6c0
> [   20.094747] [<8002b17c>] (warn_slowpath_null) from [<8058403c>] (dapm_assert_locked.isra.36+0x4c/0x58)
> [   20.104101] [<80583ff0>] (dapm_assert_locked.isra.36) from [<805842ec>] (dapm_mark_dirty+0x64/0xa4)
> [   20.113165] [<80584288>] (dapm_mark_dirty) from [<805853a8>] (soc_dapm_dai_stream_event.isra.42+0x30/0xc8)
> [   20.122863]  r8:ed9b5dbc r7:00000000 r6:00000001 r5:00000001 r4:ed83d6c0
> [   20.129706] [<80585378>] (soc_dapm_dai_stream_event.isra.42) from [<80587e28>] (snd_soc_dapm_stream_event+0x78/0xa0)
> [   20.140264]  r5:ee2ee62c r4:00000001
> [   20.143918] [<80587db0>] (snd_soc_dapm_stream_event) from [<8058957c>] (soc_pcm_prepare+0x138/0x21c)
> [   20.153058]  r8:ed8d9480 r7:00000000 r6:ed9b0e00 r5:00000001 r4:ee2ee62c r3:00000000
> ...
>
> Signed-off-by: Shengjiu Wang <shengjiu.wang at freescale.com>
> ---
>   sound/soc/soc-dapm.c |    3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
> index aa327c9..b618541 100644
> --- a/sound/soc/soc-dapm.c
> +++ b/sound/soc/soc-dapm.c
> @@ -3856,6 +3856,9 @@ static void soc_dapm_dai_stream_event(struct snd_soc_dai *dai, int stream,
>   {
>   	struct snd_soc_dapm_widget *w;
>
> +	if (snd_soc_dai_is_dummy(dai))
> +		return;
> +

While this will silence the lockdep warning the underlying issue is still 
there. When the dummy DAI is used in multiple cards for each card a set of 
widgets is created for the DAI which is then stored in 
dai->playback/capture_widget. This means the second card will overwrite the 
widgets created by the first card.

The correct way to fix this is to not create any widgets for the dummy DAI. 
This also means you can remove the dummy check in 
dapm_connect_dai_link_widgets().

>   	if (stream == SNDRV_PCM_STREAM_PLAYBACK)
>   		w = dai->playback_widget;
>   	else
>