[Intel-gfx] [PATCH 7/6] drm/i915/skl: DDI-E and DDI-A shares 4 lanes.

[Zhang, Xiong Y]

> On Wed, 2015-08-12 at 02:20 +0000, Zhang, Xiong Y wrote:
> > > On Tue, 2015-08-11 at 07:05 +0000, Zhang, Xiong Y wrote:
> > > > > -----Original Message-----
> > > > > From: Vivi, Rodrigo
> > > > > Sent: Saturday, August 8, 2015 8:34 AM
> > > > > To: intel-gfx at lists.freedesktop.org
> > > > > Cc: Vivi, Rodrigo; Zhang, Xiong Y
> > > > > Subject: [PATCH 7/6] drm/i915/skl: DDI-E and DDI-A shares 4
> > > > > lanes.
> > > > >
> > > > > DDI-A and DDI-E shares the 4 lanes. So when DDI-E is present we
> > > > > need to configure lane count propperly for both.
> > > > >
> > > > > This was based on Sonika's
> > > > > [PATCH] drm/i915/skl: Select DDIA lane capability based upon vbt
> > > > >
> > > > > Credits-to: Sonika Jindal <sonika.jindal at intel.com>
> > > > > Cc: Xiong Zhang <xiong.y.zhang at intel.com>
> > > > > Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > > > > ---
> > > > >  drivers/gpu/drm/i915/intel_ddi.c | 12 ++++++++++--
> > > > > drivers/gpu/drm/i915/intel_dp.c  |  8 +++++---
> > > > >  2 files changed, 15 insertions(+), 5 deletions(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/i915/intel_ddi.c
> > > > > b/drivers/gpu/drm/i915/intel_ddi.c
> > > > > index 110d546..557cecf 100644
> > > > > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > > > > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > > > > @@ -3178,7 +3178,15 @@ void intel_ddi_init(struct drm_device
> > > > > *dev, enum port port)
> > > > >  	struct intel_digital_port *intel_dig_port;
> > > > >  	struct intel_encoder *intel_encoder;
> > > > >  	struct drm_encoder *encoder;
> > > > > -	bool init_hdmi, init_dp;
> > > > > +	bool init_hdmi, init_dp, ddi_e_present;
> > > > > +
> > > > > +	/*
> > > > > +	 * On SKL we don't have a way to detect DDI-E so we
> > > > > rely
> > > > > on VBT.
> > > > > +	 */
> > > > > +	ddie_present = IS_SKYLAKE(dev) &&
> > > > > +		(dev_priv
> > > > > ->vbt.ddi_port_info[PORT_E].supports_dp
> > > > > > >
> > > > > +		 dev_priv
> > > > > ->vbt.ddi_port_info[PORT_E].supports_dvi
> > > > > > >
> > > > > +		 dev_priv
> > > > > ->vbt.ddi_port_info[PORT_E].supports_hdmi);
> > > > [Zhang, Xiong Y]  ddie_present should be ddi_e_present
> > > > >
> > > > >  	init_hdmi = (dev_priv
> > > > > ->vbt.ddi_port_info[port].supports_dvi ||
> > > > >  		     dev_priv
> > > > > ->vbt.ddi_port_info[port].supports_hdmi);
> > > > > @@ -3210,7 +3218,7 @@ void intel_ddi_init(struct drm_device
> > > > > *dev, enum port port)
> > > > >  	intel_dig_port->port = port;
> > > > >  	intel_dig_port->saved_port_bits =
> > > > > I915_READ(DDI_BUF_CTL(port)) &
> > > > >
> > > > >  (DDI_BUF_PORT_REVERSAL |
> > > > > -					   DDI_A_4_LANES);
> > > > > +					   ddi_e_present ? 0 :
> > > > > DDI_A_4_LANES);
> > > > [Zhang, Xiong Y] Sonika's patch will set DDI-A to 4 lanes when
> > > > DDI-E doesn't exist, I think your patch will do nothing.
> > >
> > > Actually DDI_A_4_LANES is being already set unconditionally, so
> > > Sonika's patch has no effect.
> > [Zhang, Xiong Y] No. Sonika's patch set DDI_A_4_LANES under many
> > conditions.
> > +	if (IS_SKYLAKE(dev) && port == PORT_A
> > +		&& !(val & DDI_BUF_CTL_ENABLE)
> > +		&& !dev_priv->vbt.ddi_e_used)
> > +		I915_WRITE(DDI_BUF_CTL(port), val | DDI_A_4_LANES)
> > >
> > > saved_port_bits goes to intel_dp->DP that goes to DDI_BUF_CTL and
> > > also it is used to calculate the number of lanes.
> > >
> > > With this patch we stop setting DDI_A_4_LANES when ddi_e is present
> > > so DDI-A keeps with 2 lanes and let other 2 lanes for DDI-E
> > [Zhang, Xiong Y] Yes, this patch will clear DDI_A_4_LANES when ddi_e
> > is present.
> > But this patch won't set DDI_A_4_LANES under following conditions
> > which is purpose for Sonika patch 1. Bios fail to driver eDP and
> > doesn't enable DDI_A buffer
> 
> If DDI_A isn't enabled we don't need to set DDI_A_4_LANES
[Zhang, Xiong Y] From commit message on Sonika patch, she want to 
set DDI_A_4_LANES on such case. Maybe she met such fail case on one high
resolution eDP screen. Let's Sonikia explain it.
> 
> > 2. Bios clear DDI_A_4_LANES
> > 3. DDI_E isn't present
> 
> I don't agree... This is already covered on current code. DDI_A_4_LANES is
> already being set when enabling DDI_A.
> 
> 
> >
> > thanks
> > >