[Intel-gfx] [PATCH] drm/i915: Do not reset detect_done flag in intel_dp_detect

[Manasi Navare]

Ville,
You mentioned that this detect_done should be set to false also
in the resume case so in i915_display_resume where it calls
intel_hpd_init that eventually schedules the hpd_poll_init_work and
calls drm_helper_hpd_irq_event() which then calls .detect().
So in this case if I have to reset this detect_done in the
hpd_poll_init_work, how do I make sure I do it only if the
connector is DP?

Manasi 

On Wed, Dec 07, 2016 at 04:05:56PM +0200, Ville Syrjälä wrote:
> On Tue, Dec 06, 2016 at 04:43:51PM -0800, Manasi Navare wrote:
> > The detect_done flag was introduced in the commit
> > 7d23e3c37bb3fc6952dc84007ee60cb533fd2d5c in order to avoid
> > multiple detects on hotplug where intel_dp_long_pulse()
> > was called from HPD handler as well as in intel_dp_detect.
> > So this detect_done flag was required to make sure intel_dp_detect()
> > did not call long pulse handler again if it was already been called
> > from HPD handler. However commit 1015811609c0328b5ed670d07748591b837e74eb
> > differs the long hpd handling entirely until the hotplug work runs to
> > avoid the double long hpd handling the "detect_done" flag is trying
> > to prevent.
> 
> That sentence doesn't parse here. Anyways, the flag indeed is now a nop
> and your patch is pretty much the same what I did here:
> https://patchwork.freedesktop.org/patch/101476/
> 
> > 
> > So now we do not need to reset the detect_done flag to false in
> > intel_dp_detect. It will be reset in the intel_dp_hpd_pulse so
> > that intel_dp_detect does a full detect. However if the .detect
> > gets called during mode enumeration then we do not need to do a
> > full detect. This patch avoids the WARNS_ONS during connected boot
> > case when it calls intel_dp_check_link_status() due to multiple
> > detects
> 
> How exactly does it do that? Also we shouldn't sweep that under the rug
> anyway. Instead someone should actually fix the problem that causes the
> WARN.
> 
> > and also avoids DP compliance failures. It avoids doing
> > a full detect every single time on .detect().
> > 
> > Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> > Cc: Jani Nikula <jani.nikula at linux.intel.com>
> > Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c | 2 --
> >  1 file changed, 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index db75bb9..9c9277e 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -4470,8 +4470,6 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
> >  	if (!intel_dp->detect_done)
> >  		status = intel_dp_long_pulse(intel_dp->attached_connector);
> >  
> > -	intel_dp->detect_done = false;
> > -
> >  	return status;
> >  }
> >  
> > -- 
> > 1.9.1
> 
> -- 
> Ville Syrjälä
> Intel OTC