[alsa-devel] Bad PCM stream after a suspend/resume cycle

[Mirza Krak]

On 12 January 2018 at 19:04, Takashi Iwai <tiwai at suse.de> wrote:
> On Fri, 12 Jan 2018 14:36:45 +0100,
> Mirza Krak wrote:
>>

< snip >

>
> The EBADFD is already indicating a fatal error, and something is wrong
> in the driver.  Basically the driver should suspend the stream via
> snd_pcm_suspend*() call in the PM resume ops.  Most likely your driver
> misses that.
>
> That said, it's specific to your using driver, and you'd need to take
> a look at that code there.

Thank you for you patience with me.

I have looked further in to my hardware drivers and I can not really
see any faults here.

But I did some further testing and applying the following diff on
aplay "resolves" the problem (v1.1.4 of alsa-utils):

diff --git a/aplay/aplay.c b/aplay/aplay.c
index f793c82..040cec1 100644
--- a/aplay/aplay.c
+++ b/aplay/aplay.c
@@ -2020,6 +2020,8 @@ static ssize_t pcm_write(u_char *data, size_t count)
                if (test_position)
                        do_test_position();
                if (r == -EAGAIN || (r >= 0 && (size_t)r < count)) {
+                       if (snd_pcm_state(handle) == SND_PCM_STATE_SUSPENDED)
+                               suspend();
                        if (!test_nowait)
                                snd_pcm_wait(handle, 100);
                } else if (r == -EPIPE) {

Which means that there is no error in regard to suspending the stream
as it properly reports this when checked.

My problem is that this condition:

    (r >= 0 && (size_t)r < count)

Is always true after a suspend/resume cycle. Which normally does not
result in a "resume" call from aplay nor from snd_pcm_recover, which
means that it will try to write data to a suspended stream which
results in -EBADFD due to this (from alsa-lib):

snd_pcm_sframes_t snd_pcm_writei(snd_pcm_t *pcm, const void *buffer,
snd_pcm_uframes_t size)
{
    < snip >

    if (bad_pcm_state(pcm, P_STATE_RUNNABLE))
        return -EBADFD;
    return _snd_pcm_writei(pcm, buffer, size);
}

Because SUSPENDED is not part of the P_STATE_RUNNABLE, which maybe it should be?

-- 
Med Vänliga Hälsningar / Best Regards

Mirza Krak