Re: [PATCH] ASoC: dapm: Don't check dummy dai in soc_dapm_dai_stream_event

[Lars-Peter Clausen <lars@metafoo.de>]

On 07/02/2015 11:32 AM, Shengjiu Wang wrote:
> On Thu, Jul 02, 2015 at 11:54:25AM +0200, Lars-Peter Clausen wrote:
>> On 07/02/2015 11:23 AM, Lars-Peter Clausen wrote:
>>> 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@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().
>>
>> Btw. this should affect more than just DAPM, if you have the dummy
>> DAI in multiple cards the dummy CODEC ends up getting attached to
>> both cards which should result in the component and CODEC list
>> getting corrupted.
>
> Why you think the codec list should be corrupted? I didn't meet this
> corruption. I check the codec list, there is only one "snd-soc-dummy" in it.

I guess what avoids this is that we check component->probed and don't probe 
again if it already has been probed. But there are still assumptions 
all-throughout ASoC that assume that a CODEC is only part of exactly one 
card. The dummy CODEC will need special handling to make sure that it 
doesn't get added to any card.

- Lars