Re: [PATCH] ALSA: hda: cs35l56: Perform firmware download in the background

[Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx>]

On 02/05/2024 08:34, Takashi Iwai wrote:
> On Wed, 01 May 2024 13:17:55 +0200,
> Simon Trimmer wrote:
> > @@ -964,6 +1011,14 @@ int cs35l56_hda_common_probe(struct cs35l56_hda *cs35l56, int hid, int id)
> >   	mutex_init(&cs35l56->base.irq_lock);
> >   	dev_set_drvdata(cs35l56->base.dev, cs35l56);
> >   
> > +	cs35l56->dsp_wq = create_singlethread_workqueue("cs35l56-dsp");
> > +	if (!cs35l56->dsp_wq) {
> > +		ret = -ENOMEM;
> > +		goto err;
> > +	}
>
> Do we really need a dedicated workqueue?  In most usages, simple
> schedule_work*() works fine and is recommended.

On a slow I2C bus with 4 amps this work could take over 2 seconds.
That seems too long to be blocking a global system queue. We use a
dedicated queue in the ASoC driver.

Also if we queue work on an ordered (single-threaded) system queue the
firmware won't be downloaded to multiple amps in parallel, so we don't
get the best use of the available bus bandwidth.

> thanks,
>
> Takashi