[Intel-gfx] [PATCH 06/10] drm/i915/icl: Mark TC port as safe when interruptions are disabled

[Souza, Jose]

On Tue, 2018-10-02 at 23:35 +0300, Ville Syrjälä wrote:
> On Tue, Oct 02, 2018 at 10:50:50AM -0700, José Roberto de Souza
> wrote:
> > Before enter in power saving states or before unload the driver
> > spec states that display driver is required to to mark TC ports as
> > safe so hardware can do the disconnection flow without wait for
> > display driver handshake.
> > When driver is resumed or loaded again, if the TC live state is
> > still set as connected driver will mark again TC port as not safe
> > as
> > required by spec.
> > 
> > BSpec: 2175
> > 
> > Cc: Paulo Zanoni <paulo.r.zanoni at intel.com>
> > Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_irq.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_irq.c
> > b/drivers/gpu/drm/i915/i915_irq.c
> > index 2e242270e270..58616690f45f 100644
> > --- a/drivers/gpu/drm/i915/i915_irq.c
> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > @@ -3640,6 +3640,7 @@ static void gen11_irq_reset(struct drm_device
> > *dev)
> >  {
> >  	struct drm_i915_private *dev_priv = dev->dev_private;
> >  	int pipe;
> > +	u32 val;
> >  
> >  	I915_WRITE(GEN11_GFX_MSTR_IRQ, 0);
> >  	POSTING_READ(GEN11_GFX_MSTR_IRQ);
> > @@ -3661,6 +3662,15 @@ static void gen11_irq_reset(struct
> > drm_device *dev)
> >  
> >  	if (HAS_PCH_ICP(dev_priv))
> >  		GEN3_IRQ_RESET(SDE);
> > +
> > +	/*
> > +	 * Mark TC ports as safe so hardware can do the disconnect flow
> > without
> > +	 * wait for driver to do the handshake
> > +	 */
> > +	val = I915_READ(PORT_TX_DFLEXDPCSSS);
> > +	for (pipe = 0; pipe < 4; pipe++)
> > +		val &= ~(DP_PHY_MODE_STATUS_NOT_SAFE(pipe));
> > +	I915_WRITE(PORT_TX_DFLEXDPCSSS, val);
> 
> Why would we have to do this here? The driver should relinquish
> control
> if and when it has shut down the pipes etc. Sounds like a bug if
> we're
> hanging on when we have no need for the port.

Right now we take control and only release it when port is
disconnected.

You mean release it in intel_dp_link_down()?
I guess it could be moved to that function but we would need:
- make icl_tc_port_connected() not grab control in any further calls to
intel_digital_port_connected() when driver is not using it
- to add special case to handle MST
- release control when a error happen when doing the modeset

In my opinion that would make it way more complicated with no benefit.

Also keeping it in gen11_irq_reset() would give back to HW the control
when loading the module, fixing possible problems with a BIOS that do
not release control of it before handing out system to bootloader.

> 
> >  }
> >  
> >  void gen8_irq_power_well_post_enable(struct drm_i915_private
> > *dev_priv,
> > -- 
> > 2.19.0
> > 
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