Hi Laurent,
On Sat, Nov 11, 2017 at 08:17:59AM +0200, Laurent Pinchart wrote:
> > > +static int rcar_csi2_s_power(struct v4l2_subdev *sd, int on)
> > > +{
> > > + struct rcar_csi2 *priv = sd_to_csi2(sd);
> > > +
> > > + if (on)
> > > + pm_runtime_get_sync(priv->dev);
> > > + else
> > > + pm_runtime_put(priv->dev);
> >
> > The pipeline you have is already rather complex. Would it be an option to
> > power the hardware on when streaming is started? The smiapp driver does
> > this, without even implementing the s_power callback. (You'd still need to
> > call it on the image source, as long as we have drivers that need it.)
>
> We've briefly discussed this before, and I agree that pipeline power
> management needs to be redesigned, but we still haven't agreed on a proper
> architecture for that. Feel free to propose an RFC :-) In the meantime I
Well, perhaps we should look at the use cases and see if there are gaps.
Runtime PM is essentially used everywhere else in the kernel.
> wouldn't try to enforce one specific model.
What I just wanted to point out that by switching to runtime PM you avoid
adding a new driver which is dependent on the s_power callback which I
don't think we'll want to keep in the long run. In this case there's no
benefit from s_power in any quantifiable way that I can see.
Actually the master driver manages calling the s_power callback so there's
hardly a need to do so here. It's just that the master drivers still need
that as long as there are sub-device drivers that depend on it.
--
Regards,
Sakari Ailus
e-mail: sakari.ailus@xxxxxx
