Re: [PATCH v2] drm/i915/lspcon: Enable AUX interrupts for resume time initialization

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Nov 29, 2016 at 10:14:23PM +0200, Imre Deak wrote:
> On Tue, 2016-11-29 at 21:55 +0200, Ville Syrjälä wrote:
> > On Tue, Nov 29, 2016 at 09:40:29PM +0200, Imre Deak wrote:
> > > For LSPCON initialization during system resume we need AUX
> > > functionality, but we call the corresponding encoder reset hook with all
> > > interrupts disabled. Without interrupts we'll do a poll-wait for AUX
> > > transfer completions, which adds a significant delay if the transfers
> > > timeout/need to be retried for some reason.
> > > 
> > > Fix this by enabling interrupts before calling the reset hooks. Note
> > > that while this will enable AUX interrupts it will keep HPD interrupts
> > > disabled, in a similar way to the init time output setup code.
> > > 
> > > This issue existed since LSPCON support was added.
> > > 
> > > v2:
> > > - Rebased on drm-tip.
> > > 
> > > Cc: Shashank Sharma <shashank.sharma@intel.com>
> > > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_drv.c | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > > index 8dac298..2cea2ef 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.c
> > > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > > @@ -1582,18 +1582,21 @@ static int i915_drm_resume(struct drm_device *dev)
> > >  	intel_opregion_setup(dev_priv);
> > >  
> > >  	intel_init_pch_refclk(dev_priv);
> > > -	drm_mode_config_reset(dev);
> > >  
> > >  	/*
> > >  	 * Interrupts have to be enabled before any batches are run. If not the
> > >  	 * GPU will hang. i915_gem_init_hw() will initiate batches to
> > >  	 * update/restore the context.
> > >  	 *
> > > +	 * drm_mode_config_reset() needs AUX interrupts.
> > > +	 *
> > >  	 * Modeset enabling in intel_modeset_init_hw() also needs working
> > >  	 * interrupts.
> > >  	 */
> > >  	intel_runtime_pm_enable_interrupts(dev_priv);
> > >  
> > > +	drm_mode_config_reset(dev);
> > > +
> > 
> > Didn't look like anything should seriously explode.
> > 
> > Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > There is a slight concern on g4x/vlv/chv that an AUX interrupts would
> > trigger the hpd irq handler, which doesn't realize it's supposed to
> > ignore the actual hpd bits in PORT_HOTPLUG_STAT. So any aux before we
> > enable hpd processing for real could do something bad. So I guess we
> > should add some kind of software tracking for that stuff like we have
> > for PIPESTAT.
> 
> Didn't think about that, but BSpec tells me those are masked by the HPD
> IRQ enable bits in PORT_HOTPLUG_EN and those we enable only later.
> Otherwise this would be also a problem during output setup time.

Hmm. Are they really masked? I though it's just an IER effectively.

> 
> --Imre
> 
> > 
> > >  	mutex_lock(&dev->struct_mutex);
> > >  	if (i915_gem_init_hw(dev)) {
> > >  		DRM_ERROR("failed to re-initialize GPU, declaring wedged!\n");
> > > -- 
> > > 2.5.0
> > > 
> > > _______________________________________________
> > > Intel-gfx mailing list
> > > Intel-gfx@lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> > 

-- 
Ville Syrjälä
Intel OTC
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