drm/i915/dp: Configure i915 Picture parameter Set registers during DSC enabling

After encoder->pre_enable() hook, after link training sequence is
completed, PPS registers for DSC encoder are configured using the
DSC state parameters in intel_crtc_state as part of DSC enabling
routine in the source. DSC enabling routine is called after
encoder->pre_enable() before enbaling the pipe and after
compression is enabled on the sink.

v7:
* Remove unnecessary comments, leftovers (Ville)
* No need for explicit val &= ~ (Ville)
v6:
intel_dsc_enable to be part of pre_enable hook (Ville)
v5:
* make crtc_state const (Ville)
v4:
* Use cpu_transcoder instead of encoder->type for using EDP transcoder
DSC registers(Ville)
* Keep all PSS regs together (Anusha)

v3:
* Configure Pic_width/2 for each VDSC engine when two VDSC engines per pipe
are used (Manasi)
* Add DSC slice_row_per_frame in PPS16 (Manasi)

v2:
* Enable PG2 power well for VDSC on eDP

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
[manasi: fixup the line longer than 100 chars while applying]
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181128202628.20238-8-manasi.d.navare@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -3340,6 +3340,8 @@ extern void intel_rps_mark_interactive(struct drm_i915_private *i915,
 				       bool interactive);
 extern bool intel_set_memory_cxsr(struct drm_i915_private *dev_priv,
 				  bool enable);
+void intel_dsc_enable(struct intel_encoder *encoder,
+		      const struct intel_crtc_state *crtc_state);
 
 int i915_reg_read_ioctl(struct drm_device *dev, void *data,
 			struct drm_file *file);

drivers/gpu/drm/i915/intel_ddi.c

@@ -3144,6 +3144,8 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
 
 	if (!is_mst)
 		intel_ddi_enable_pipe_clock(crtc_state);
+
+	intel_dsc_enable(encoder, crtc_state);
 }
 
 static void intel_ddi_pre_enable_hdmi(struct intel_encoder *encoder,