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

Vivi, Rodrigo
2015-08-12T16:51:59Z

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
> >