[Intel-gfx] [PATCH v5 2/6] drm/i915/pxp: add device link between i915 and mei_pxp

[Usyskin, Alexander]

> > diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp_tee.c
> b/drivers/gpu/drm/i915/pxp/intel_pxp_tee.c
> > index d50354bfb993..bef6d7f8ac55 100644
> > --- a/drivers/gpu/drm/i915/pxp/intel_pxp_tee.c
> > +++ b/drivers/gpu/drm/i915/pxp/intel_pxp_tee.c
> > @@ -127,6 +127,10 @@ static int i915_pxp_tee_component_bind(struct
> device *i915_kdev,
> >  	intel_wakeref_t wakeref;
> >  	int ret = 0;
> >
> > +	if (!HAS_HECI_PXP(i915) &&
> > +	    drm_WARN_ON(&i915->drm, !device_link_add(i915_kdev,
> tee_kdev,
> 
> I don't like the action here hidden behind the drm_WARN_ON.
> Please notice that almost every use of this and other helpers like
> this expect the param as a failure. Not an actual action. So,
> most of lazy readers like me might ignore that the main function
> is actually a param inside  this warn condition.
> 
Honestly, copy-pasted from drivers/gpu/drm/i915/display/intel_audio.c +1266
I don't have deep knowledge of drm macros, so thought this should be ok.
Can make it any other form that acceptable in drm tree...

> We should probably stash the link as well...
> 
> pxp->dev_link = device_link_add(i915_kdev, tee_kdev,...);
> 
> so in the end below, instead of checking the HAS_HECI_PXP again
> and use the remove version you check the dev_link and use the del
> function.
> 
> something like:
> 
> if (pxp->dev_link)
>    device_link_del(pxp->dev_link);
> 
Not sure that this simplification warrants additional clutter in struct.

> Also, do you really need the WARN to see the stack when this happens
> or you already know the callers?
> Why not a simple drm_error msg?
> 
> if (!HAS_HECI_PXP(i915) {
> 	pxp->dev_link = device_link_add(i915_kdev, tee_kdev,...);
> 	if (!pxp->dev_link) {
> 	   drm_error();
> 	   return -ESOMETHING;
> 
> >  DL_FLAG_STATELESS)))
> 
> do we need the RPM in sync as well?
> I mean:
> 
> DL_FLAG_STATELESS | DL_FLAG_PM_RUNTIME)))
> 
> ?

No, the mei device should not be active all the time when i915 is active, only when pxp requires it.

> 
> > +		return -ENOMEM;
> 
> why ENOMEM?
Copy-paste from i915 audio.

> 
> > +
> >  	mutex_lock(&pxp->tee_mutex);
> >  	pxp->pxp_component = data;
> >  	pxp->pxp_component->tee_dev = tee_kdev;
> > @@ -169,6 +173,9 @@ static void i915_pxp_tee_component_unbind(struct
> device *i915_kdev,
> >  	mutex_lock(&pxp->tee_mutex);
> >  	pxp->pxp_component = NULL;
> >  	mutex_unlock(&pxp->tee_mutex);
> > +
> > +	if (!HAS_HECI_PXP(i915))
> > +		device_link_remove(i915_kdev, tee_kdev);
> >  }
> >
> >  static const struct component_ops i915_pxp_tee_component_ops = {
> > --
> > 2.39.0
> >