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

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Sun, Jan 22, 2023 at 06:57:24AM +0000, Usyskin, Alexander wrote:
> > > 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...

something like I suggested in my previous reply please.

> 
> > 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.

okay then

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

It doesn't make sense to me.
Looking to other derivers -ENODEV or -EINVAL seems to be
the most used choices...

looking to the error codes probably ECHILD would make sense
but no one is using it... so let's stay with ENODEV?!

> 
> > 
> > > +
> > >  	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
> > >