Re: [PATCH 2/2] drm/i915: Ignore long hpds on eDP ports

Ville Syrjälä
2014-10-17T09:01:05Z

On Fri, Oct 17, 2014 at 11:49:54AM +0300, Jani Nikula wrote:
> On Thu, 16 Oct 2014, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > Turning vdd on/off can generate a long hpd pulse on eDP ports. In order
> > to handle hpd we would need to turn on vdd to perform aux transfers.
> > This would lead to an endless cycle of
> > "vdd off -> long hpd -> vdd on -> detect -> vdd off -> ..."
> >
> > So ignore long hpd pulses on eDP ports. eDP panels should be physically
> > tied to the machine anyway so they should not actually disappear and
> > thus don't need long hpd handling. Short hpds are still needed for link
> > re-train and whatnot so we can't just turn off the hpd interrupt
> > entirely for eDP ports. Perhaps we could turn it off whenever the panel
> > is disabled, but just ignoring the long hpd seems sufficient.
>
> Did you test this with my short vs. long hpd fix applied?

Yes. Well, with my own version of it :)

Now someone should go and implement HPD support for port A.

>
> In any case, makes sense,
>
> Reviewed-by: Jani Nikula <jani.nikula@intel.com>
>
>
>
>
>
> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> > drivers/gpu/drm/i915/intel_dp.c | 12 ++++++++++++
> > 1 file changed, 12 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index f07f02c..4455009 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -4611,6 +4611,18 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
> > if (intel_dig_port->base.type != INTEL_OUTPUT_EDP)
> > intel_dig_port->base.type = INTEL_OUTPUT_DISPLAYPORT;
> >
> > + if (long_hpd && intel_dig_port->base.type == INTEL_OUTPUT_EDP) {
> > + /*
> > + * vdd off can generate a long pulse on eDP which
> > + * would require vdd on to handle it, and thus we
> > + * would end up in an endless cycle of
> > + * "vdd off -> long hpd -> vdd on -> detect -> vdd off -> ..."
> > + */
> > + DRM_DEBUG_KMS("ignoring long hpd on eDP port %c\n",
> > + port_name(intel_dig_port->port));
> > + return false;
> > + }
> > +
> > DRM_DEBUG_KMS("got hpd irq on port %c - %s\n",
> > port_name(intel_dig_port->port),
> > long_hpd ? "long" : "short");
> > --
> > 2.0.4
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Jani Nikula, Intel Open Source Technology Center

--
Ville Syrjälä
Intel OTC