Re: [PATCH v2] drm/i915: Improve DP downstream HPD handling

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

On Fri, Oct 27, 2017 at 01:02:24PM +0300, Jani Nikula wrote:
> On Fri, 27 Oct 2017, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > DP dongles may signal downstream HPD via short HPD pulses. Setting the
> > sink to DPMS off apparently kills the downstream HPD (at least on my
> > DP->VGA dongle), so skip the DPMS off for such dongles when we turn
> > off the port.
> >
> > v2: Deal with DDI as well by moving the check into
> >     intel_dp_sink_dpms() (Dhinakaran)
> >
> > Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> > Cc: David Woodhouse <dwmw2@infradead.org>
> > Cc: Imre Deak <imre.deak@intel.com>
> > Cc: Pablo <pablodebiase@nanalysis.com>
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103472
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99114
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>

Thanks for the review. Patch pushed to dinq.

> 
> 
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index aa75f55eeb61..59169a4dc9d3 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -2505,6 +2505,21 @@ static void ironlake_edp_pll_off(struct intel_dp *intel_dp)
> >  	udelay(200);
> >  }
> >  
> > +static bool downstream_hpd_needs_d0(struct intel_dp *intel_dp)
> > +{
> > +	/*
> > +	 * DPCD 1.2+ should support BRANCH_DEVICE_CTRL, and thus
> > +	 * be capable of signalling downstream hpd with a long pulse.
> > +	 * Whether or not that means D3 is safe to use is not clear,
> > +	 * but let's assume so until proven otherwise.
> > +	 *
> > +	 * FIXME should really check all downstream ports...
> > +	 */
> > +	return intel_dp->dpcd[DP_DPCD_REV] == 0x11 &&
> > +		intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT &&
> > +		intel_dp->downstream_ports[0] & DP_DS_PORT_HPD;
> > +}
> > +
> >  /* If the sink supports it, try to set the power state appropriately */
> >  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode)
> >  {
> > @@ -2515,6 +2530,9 @@ void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode)
> >  		return;
> >  
> >  	if (mode != DRM_MODE_DPMS_ON) {
> > +		if (downstream_hpd_needs_d0(intel_dp))
> > +			return;
> > +
> >  		ret = drm_dp_dpcd_writeb(&intel_dp->aux, DP_SET_POWER,
> >  					 DP_SET_POWER_D3);
> >  	} else {
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center

-- 
Ville Syrjälä
Intel OTC
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