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

["Vivi, Rodrigo" <rodrigo.vivi@intel.com>]

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@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@intel.com>
> > > > Cc: Xiong Zhang <xiong.y.zhang@intel.com>
> > > > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@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

> 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
> > 
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