drm/i915/dp: Add a standalone function to obtain shared dpll for HSW/BDW/SKL/BXT

Add the PLL selection code for HSW/BDW/BXT/SKL into a stand-alone function
in order to allow for the implementation of a platform neutral upfront
link training function.

v4:
* Removed dereferencing NULL pointer in case of failure (Dhinakaran Pandiyan)
v3:
* Add Hooks for all DDI platforms into this standalone function

v2:
* Change the macro to use dev_priv instead of dev (David Weinehall)

Reviewed-by: Durgadoss R <[e-mail]>
Signed-off-by: Manasi Navare <[e-mail]>
Signed-off-by: Jim Bride <[e-mail]>
Signed-off-by: Rodrigo Vivi <[e-mail]>

drivers/gpu/drm/i915/intel_ddi.c

···
 	return connector;
 }
 
+struct intel_shared_dpll *
+intel_ddi_get_link_dpll(struct intel_dp *intel_dp, int clock)
+{
+	struct intel_connector *connector = intel_dp->attached_connector;
+	struct intel_encoder *encoder = connector->encoder;
+	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
+	struct intel_shared_dpll *pll = NULL;
+	struct intel_shared_dpll_config tmp_pll_config;
+	enum intel_dpll_id dpll_id;
+
+	if (IS_BROXTON(dev_priv)) {
+		dpll_id =  (enum intel_dpll_id)dig_port->port;
+		/*
+		 * Select the required PLL. This works for platforms where
+		 * there is no shared DPLL.
+		 */
+		pll = &dev_priv->shared_dplls[dpll_id];
+		if (WARN_ON(pll->active_mask)) {
+
+			DRM_ERROR("Shared DPLL in use. active_mask:%x\n",
+				  pll->active_mask);
+			return NULL;
+		}
+		tmp_pll_config = pll->config;
+		if (!bxt_ddi_dp_set_dpll_hw_state(clock,
+						  &pll->config.hw_state)) {
+			DRM_ERROR("Could not setup DPLL\n");
+			pll->config = tmp_pll_config;
+			return NULL;
+		}
+	} else if (IS_SKYLAKE(dev_priv)) {
+		pll = skl_find_link_pll(dev_priv, clock);
+	} else if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv)) {
+		pll = hsw_ddi_dp_get_dpll(encoder, clock);
+	}
+	return pll;
+}
+
 void intel_ddi_init(struct drm_device *dev, enum port port)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);

drivers/gpu/drm/i915/intel_dpll_mgr.c

···
 #include "intel_drv.h"
 
 struct intel_shared_dpll *
+skl_find_link_pll(struct drm_i915_private *dev_priv, int clock)
+{
+	struct intel_shared_dpll *pll = NULL;
+	struct intel_dpll_hw_state dpll_hw_state;
+	enum intel_dpll_id i;
+	bool found = false;
+
+	if (!skl_ddi_dp_set_dpll_hw_state(clock, &dpll_hw_state))
+		return pll;
+
+	for (i = DPLL_ID_SKL_DPLL1; i <= DPLL_ID_SKL_DPLL3; i++) {
+		pll = &dev_priv->shared_dplls[i];
+
+		/* Only want to check enabled timings first */
+		if (pll->config.crtc_mask == 0)
+			continue;
+
+		if (memcmp(&dpll_hw_state, &pll->config.hw_state,
+			   sizeof(pll->config.hw_state)) == 0) {
+			found = true;
+			break;
+		}
+	}
+
+	/* Ok no matching timings, maybe there's a free one? */
+	for (i = DPLL_ID_SKL_DPLL1;
+	     ((found == false) && (i <= DPLL_ID_SKL_DPLL3)); i++) {
+		pll = &dev_priv->shared_dplls[i];
+		if (pll->config.crtc_mask == 0) {
+			pll->config.hw_state = dpll_hw_state;
+			break;
+		}
+	}
+
+	return pll;
+}
+
+struct intel_shared_dpll *
 intel_get_shared_dpll_by_id(struct drm_i915_private *dev_priv,
 			    enum intel_dpll_id id)
 {

drivers/gpu/drm/i915/intel_dpll_mgr.h

···
 /* SKL dpll related functions */
 bool skl_ddi_dp_set_dpll_hw_state(int clock,
 				  struct intel_dpll_hw_state *dpll_hw_state);
+struct intel_shared_dpll *skl_find_link_pll(struct drm_i915_private *dev_priv,
+					    int clock);
 
 
 /* HSW dpll related functions */

drivers/gpu/drm/i915/intel_drv.h

···
 			 struct intel_crtc_state *pipe_config);
 void intel_ddi_set_vc_payload_alloc(struct drm_crtc *crtc, bool state);
 uint32_t ddi_signal_levels(struct intel_dp *intel_dp);
-
+struct intel_shared_dpll *intel_ddi_get_link_dpll(struct intel_dp *intel_dp,
+						  int clock);
 unsigned int intel_fb_align_height(struct drm_device *dev,
 				   unsigned int height,
 				   uint32_t pixel_format,