[PATCH] soundwire: intel: trap TRIGGER_SUSPEND in .trigger callback

[Vinod Koul]

On 02-08-21, 10:46, Pierre-Louis Bossart wrote:
> 
> >>>>>> The trigger callback is handled in the stream lock atomically,
> >>>>>> and are you sure that you want to operate a possibly heavy task there?
> >>>>>
> >>>>> It's a good objection that we didn't think of.
> >>>>
> >>>> Doesn't Intel use non atomic trigger to send IPCs which anyway
> >>>> involve code which can sleep..?
> >>>
> >>> sof_sdw.c doesn't seem setting it?
> >>
> >> Yes I think init_dai_link() should set it. Maybe Pierre/Bard would know why.
> > 
> > init_dai_link() is to assign dai link elements only. No IPC is needed.
> 
> The 'nonatomic' concept is only used for an FE dailink which expose a
> PCM device:
> 
> soc-pcm.c:	pcm->nonatomic = rtd->dai_link->nonatomic;
> 
> Setting a BE dailink as 'nonatomic' would not accomplish much since BEs
> use the 'no_pcm' option.

are no_pcm & nonatomic supposed to be not used together? So if FE is
nonatomic would BE trigger be atomic or nonatomic?

> So the question is: is there any issue with sending an IPC in a DAI
> trigger callback?

Sorry looks like we diverged, orignal question was can we do heavy tasks
in trigger, the answer is no, unless one uses nonatomic flag which was
added so that people can do that work with DSPs like sending IPCs..
Maybe we should add heavy slimbus/soundwire handling to it too...?

> This is not very different from sending a command on a
> bus btw, I see a similar example for SLIMbus devices:
> 
> wcd9335.c:      case SNDRV_PCM_TRIGGER_SUSPEND:
> wcd9335.c-      case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
> wcd9335.c-              slim_stream_unprepare(dai_data->sruntime);
> wcd9335.c-              slim_stream_disable(dai_data->sruntime);
> 
> int slim_stream_unprepare(struct slim_stream_runtime *stream)
> {
> 	int i;
> 
> 	for (i = 0; i < stream->num_ports; i++)
> 		slim_disconnect_port(stream, &stream->ports[i]);
> 
> static int slim_disconnect_port(struct slim_stream_runtime *stream,
> 				struct slim_port *port)
> {
> 	struct slim_device *sdev = stream->dev;
> 	u8 wbuf[1];
> 	struct slim_val_inf msg = {0, 1, NULL, wbuf, NULL};
> 	u8 mc = SLIM_MSG_MC_DISCONNECT_PORT;
> 	DEFINE_SLIM_LDEST_TXN(txn, mc, 5, stream->dev->laddr, &msg);
> 
> 	wbuf[0] = port->id;
> 	port->ch.state = SLIM_CH_STATE_DISCONNECTED;
> 	port->state = SLIM_PORT_DISCONNECTED;
> 
> 	return slim_do_transfer(sdev->ctrl, &txn);
> }
> 
> Such commands may take time...

Agree, so users should be recommended to use nonatomic triggers.

-- 
~Vinod