[alsa-devel] [PATCH] ASoC: rsnd: stop all working stream when .remove

[Takashi Iwai]

On Mon, 04 Sep 2017 19:44:36 +0200,
Kuninori Morimoto wrote:
> 
> Hi Takasi-san
> 
> > > The lack of stop sync is a known problem in the ALSA PCM 
> > > infrastructure.  The standard idiom is to do sync at both prepare 
> > > and hw_free (or close) callbacks.
> > 
> > Thanks.
> > This path main sync is for clk ON/OFF
> >
> > Hm, but it's managed as PCM trigger, no?
> > How can the rsnd_io_is_working() return true after PCM streams are stopped?
> 
> It is based on PCM trigger, thus, it returns false if PCM streams are stopped.
> 
> This driver calls clk_get() when PCM started, and clk_put() when stopped.
> And it calles clk_enable() on .probe, and clk_disable() on .remove.
> 
> My problem is that user unbinds driver during Sound playing, this
> means clk_get() is called, but clk_put() is not called.
>
>Then, .remove will call clk_disable(), but clk_put() is not yet called. Then, kernel indicates clk user count mismatch. This patch calls missing PCM stop (= clk_put()) position function if needed.
> Is this clear answer for you ?

This isn't something you shouldn't fiddle with the codec layer.
If the driver gets removed during the operation, you have to cancel
the operation and sync with it in a proper way, then proceed the rest
of the remove, not only a codec-specific resource management.

Admittedly, there is no common infrastructure for that.  But it
doesn't mean that each codec driver should do its own hack.

I can imagine a way like calling the card disconnect/free at codec
remove, so that it can sync with the whole stop operation before doing
the rest.  This should be ignored when the code path is from the card
removal -- e.g. checking card->shutdown flag.


thanks,

Takashi