Re: [PATCH v1 10/11] ALSA: hda: cs35l41: Add device_link between HDA and cs35l41_hda

[Stefan Binding]

On 20/07/2023 15:21, Takashi Iwai wrote:
> On Thu, 20 Jul 2023 15:31:46 +0200,
> Stefan Binding wrote:
> > To ensure consistency between the HDA core and the CS35L41 HDA
> > driver, add a device_link between them. This ensures that the
> > HDA core will suspend first, and resume second, meaning the
> > amp driver will not miss any events from the playback hook from
> > the HDA core during system suspend and resume.
> >
> > Signed-off-by: Stefan Binding <sbinding@xxxxxxxxxxxxxxxxxxxxx>
> > ---
> >   sound/pci/hda/cs35l41_hda.c | 13 ++++++++++++-
> >   1 file changed, 12 insertions(+), 1 deletion(-)
> >
> > diff --git a/sound/pci/hda/cs35l41_hda.c b/sound/pci/hda/cs35l41_hda.c
> > index 70aa819cfbd64..175378cdf9dfa 100644
> > --- a/sound/pci/hda/cs35l41_hda.c
> > +++ b/sound/pci/hda/cs35l41_hda.c
> > @@ -1063,6 +1063,7 @@ static int cs35l41_hda_bind(struct device *dev, struct device *master, void *mas
> >   {
> >   	struct cs35l41_hda *cs35l41 = dev_get_drvdata(dev);
> >   	struct hda_component *comps = master_data;
> > +	unsigned int sleep_flags;
> >   	int ret = 0;
> >   
> >   	if (!comps || cs35l41->index < 0 || cs35l41->index >= HDA_MAX_COMPONENTS)
> > @@ -1102,6 +1103,11 @@ static int cs35l41_hda_bind(struct device *dev, struct device *master, void *mas
> >   
> >   	mutex_unlock(&cs35l41->fw_mutex);
> >   
> > +	sleep_flags = lock_system_sleep();
> > +	if (!device_link_add(&comps->codec->core.dev, cs35l41->dev, DL_FLAG_STATELESS))
> > +		dev_warn(dev, "Unable to create device link\n");
> > +	unlock_system_sleep(sleep_flags);
> Is lock_system_sleep() mandatory for device_link_add()?  The function
> takes its rw lock for the race, I suppose.

I believe this is mandatory, to ensure we don't try to add the device 
link during a suspend/resume transition.
Its probably unlikely that that would occur during the component bind, 
but just in case.

Thanks,

Stefan

> thanks,
>
> Takashi