[Intel-gfx] [PATCH] drm/i915: Fix eDP low vswing for Broadwell

[Mika Kahola]

On Wed, 2016-03-16 at 11:49 +0200, Jani Nikula wrote:
> On Wed, 16 Mar 2016, Mika Kahola <mika.kahola at intel.com> wrote:
> > [ text/plain ]
> > It was noticed on bug #94087 that module parameter
> > i915.edp_vswing=2 that should override the VBT setting
> > to use default voltage swing (400 mV) was not applied
> > for Broadwell.
> >
> > This patch provides a fix for this by checking if default
> > i.e. higher voltage swing is requested to be used and
> > applies the DDI translations table for DP instead of eDP
> > (low vswing) table.
> >
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94087
> > Signed-off-by: Mika Kahola <mika.kahola at intel.com>
> 
> cc: stable?
> 
> > ---
> >  drivers/gpu/drm/i915/intel_ddi.c | 14 ++++++++++++--
> >  1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> > index ab025a5..e30adcd 100644
> > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > @@ -443,9 +443,19 @@ void intel_prepare_ddi_buffer(struct intel_encoder *encoder)
> >  	} else if (IS_BROADWELL(dev_priv)) {
> >  		ddi_translations_fdi = bdw_ddi_translations_fdi;
> >  		ddi_translations_dp = bdw_ddi_translations_dp;
> > -		ddi_translations_edp = bdw_ddi_translations_edp;
> > +
> > +		if (dev_priv->edp_low_vswing)
> > +			ddi_translations_edp = bdw_ddi_translations_edp;
> > +		else
> > +			ddi_translations_edp = bdw_ddi_translations_dp;
> > +
> >  		ddi_translations_hdmi = bdw_ddi_translations_hdmi;
> > -		n_edp_entries = ARRAY_SIZE(bdw_ddi_translations_edp);
> > +
> > +		if (dev_priv->edp_low_vswing)
> > +			n_edp_entries = ARRAY_SIZE(bdw_ddi_translations_edp);
> > +		else
> > +			n_edp_entries = ARRAY_SIZE(bdw_ddi_translations_dp);
> > +
> 
> Please just put these in one if statement above, instead of having two.
> 
Ok, I'll fix those if statements. I'll throw a second version for a
review.

Cheers,
Mika

> BR,
> Jani.
> 
> >  		n_dp_entries = ARRAY_SIZE(bdw_ddi_translations_dp);
> >  		n_hdmi_entries = ARRAY_SIZE(bdw_ddi_translations_hdmi);
> >  		hdmi_default_entry = 7;
>