Re: [PATCH 2/4] drm/i915: cancel hotplug and dig_port work during suspend and unload

[Imre Deak <imre.deak@intel.com>]

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On Tue, 2014-08-12 at 15:53 +0300, Ville Syrjälä wrote:
> On Tue, Aug 12, 2014 at 03:36:01PM +0300, Imre Deak wrote:
> > On Tue, 2014-08-12 at 15:13 +0300, Ville Syrjälä wrote:
> > > On Mon, Aug 11, 2014 at 09:54:15PM +0300, Imre Deak wrote:
> > > > Make sure these work handlers don't run after we system suspend or
> > > > unload the driver. Note that we don't cancel the handlers during runtime
> > > > suspend. That could lead to a lockup, since we take a runtime PM ref
> > > > from the handlers themselves. Fortunaltely canceling there is not needed
> > > > since the RPM ref itself provides for the needed serialization.
> > > > 
> > > > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > > > ---
> > > >  drivers/gpu/drm/i915/i915_drv.c      | 8 ++++++++
> > > >  drivers/gpu/drm/i915/i915_drv.h      | 1 +
> > > >  drivers/gpu/drm/i915/intel_display.c | 3 +--
> > > >  3 files changed, 10 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > > > index ec96f9a..0653761 100644
> > > > --- a/drivers/gpu/drm/i915/i915_drv.c
> > > > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > > > @@ -494,6 +494,13 @@ bool i915_semaphore_is_enabled(struct drm_device *dev)
> > > >  	return true;
> > > >  }
> > > >  
> > > > +void intel_hpd_cancel_work(struct drm_i915_private *dev_priv)
> > > > +{
> > > > +	cancel_work_sync(&dev_priv->hotplug_work);
> > > > +	cancel_work_sync(&dev_priv->dig_port_work);
> > > 
> > > Since dig_port_work can queue a hotplug_work shouldn't these two be
> > > swapped?
> > 
> > Right, will fix that.
> > 
> > > I wonder if we should also clear hpd_event_bits and
> > > {long,short}_hpd_port_mask before cancelling the works? At least it
> > > might make the works end a bit quicker if the are already running.
> > 
> > Makes sense for speed, will fix it. Another thing is that a final
> > instance of these works can now run with interrupts disabled that could
> > cause DP AUX timeouts for example. That could be avoided for example by
> > adding a new dev_priv->hpd_irqs_disabled flag and setting it before
> > disabling interrupts, but I didn't want to make things more complicated
> > before getting some feedback.
> > 
> > > I also noticed that we don't seem to grab any rpm/powerwell references
> > > in ->hpd_pulse() or i915_digport_work_func(). That doesn't seem right.
> > > Or maybe you already addressed that in another patch?
> > 
> > No, I haven't. I thought it's enough that all low level functions like
> > DPCD read, link training do take already the needed refs. Isn't that
> > enough?
> 
> There's at least the call to ibx_digital_port_connected() which isn't
> covered by any rpm/powerwell reference.

Right, haven't noticed :/ I can fix this by taking the display port
power domain around ->hpd_pulse(), similar to all the other DP
encoder/connector handlers (get_modes, detect etc.). 

--Imre

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