diff --git a/Documentation/gpu/i915.rst b/Documentation/gpu/i915.rst
index 3843ef688341..104296dffad1 100644
--- a/Documentation/gpu/i915.rst
+++ b/Documentation/gpu/i915.rst
@@ -213,6 +213,18 @@ Video BIOS Table (VBT)
 .. kernel-doc:: drivers/gpu/drm/i915/intel_vbt_defs.h
    :internal:
 
+Display PLLs
+------------
+
+.. kernel-doc:: drivers/gpu/drm/i915/intel_dpll_mgr.c
+   :doc: Display PLLs
+
+.. kernel-doc:: drivers/gpu/drm/i915/intel_dpll_mgr.c
+   :internal:
+
+.. kernel-doc:: drivers/gpu/drm/i915/intel_dpll_mgr.h
+   :internal:
+
 Memory Management and Command Submission
 ========================================
 
diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.c b/drivers/gpu/drm/i915/intel_dpll_mgr.c
index 2db1d02edf93..44c3c7056f3f 100644
--- a/drivers/gpu/drm/i915/intel_dpll_mgr.c
+++ b/drivers/gpu/drm/i915/intel_dpll_mgr.c
@@ -23,6 +23,25 @@
 
 #include "intel_drv.h"
 
+/**
+ * DOC: Display PLLs
+ *
+ * Display PLLs used for driving outputs vary by platform. While some have
+ * per-pipe or per-encoder dedicated PLLs, others allow the use of any PLL
+ * from a pool. In the latter scenario, it is possible that multiple pipes
+ * share a PLL if their configurations match.
+ *
+ * This file provides an abstraction over display PLLs. The function
+ * intel_shared_dpll_init() initializes the PLLs for the given platform.  The
+ * users of a PLL are tracked and that tracking is integrated with the atomic
+ * modest interface. During an atomic operation, a PLL can be requested for a
+ * given CRTC and encoder configuration by calling intel_get_shared_dpll() and
+ * a previously used PLL can be released with intel_release_shared_dpll().
+ * Changes to the users are first staged in the atomic state, and then made
+ * effective by calling intel_shared_dpll_swap_state() during the atomic
+ * commit phase.
+ */
+
 struct intel_shared_dpll *
 skl_find_link_pll(struct drm_i915_private *dev_priv, int clock)
 {
@@ -61,6 +80,14 @@ skl_find_link_pll(struct drm_i915_private *dev_priv, int clock)
 	return pll;
 }
 
+/**
+ * intel_get_shared_dpll_by_id - get a DPLL given its id
+ * @dev_priv: i915 device instance
+ * @id: pll id
+ *
+ * Returns:
+ * A pointer to the DPLL with @id
+ */
 struct intel_shared_dpll *
 intel_get_shared_dpll_by_id(struct drm_i915_private *dev_priv,
 			    enum intel_dpll_id id)
@@ -68,6 +95,14 @@ intel_get_shared_dpll_by_id(struct drm_i915_private *dev_priv,
 	return &dev_priv->shared_dplls[id];
 }
 
+/**
+ * intel_get_shared_dpll_id - get the id of a DPLL
+ * @dev_priv: i915 device instance
+ * @pll: the DPLL
+ *
+ * Returns:
+ * The id of @pll
+ */
 enum intel_dpll_id
 intel_get_shared_dpll_id(struct drm_i915_private *dev_priv,
 			 struct intel_shared_dpll *pll)
@@ -96,6 +131,13 @@ void assert_shared_dpll(struct drm_i915_private *dev_priv,
 			pll->name, onoff(state), onoff(cur_state));
 }
 
+/**
+ * intel_prepare_shared_dpll - call a dpll's prepare hook
+ * @crtc: CRTC which has a shared dpll
+ *
+ * This calls the PLL's prepare hook if it has one and if the PLL is not
+ * already enabled. The prepare hook is platform specific.
+ */
 void intel_prepare_shared_dpll(struct intel_crtc *crtc)
 {
 	struct drm_device *dev = crtc->base.dev;
@@ -118,12 +160,10 @@ void intel_prepare_shared_dpll(struct intel_crtc *crtc)
 }
 
 /**
- * intel_enable_shared_dpll - enable PCH PLL
- * @dev_priv: i915 private structure
- * @pipe: pipe PLL to enable
+ * intel_enable_shared_dpll - enable a CRTC's shared DPLL
+ * @crtc: CRTC which has a shared DPLL
  *
- * The PCH PLL needs to be enabled before the PCH transcoder, since it
- * drives the transcoder clock.
+ * Enable the shared DPLL used by @crtc.
  */
 void intel_enable_shared_dpll(struct intel_crtc *crtc)
 {
@@ -164,6 +204,12 @@ void intel_enable_shared_dpll(struct intel_crtc *crtc)
 	mutex_unlock(&dev_priv->dpll_lock);
 }
 
+/**
+ * intel_disable_shared_dpll - disable a CRTC's shared DPLL
+ * @crtc: CRTC which has a shared DPLL
+ *
+ * Disable the shared DPLL used by @crtc.
+ */
 void intel_disable_shared_dpll(struct intel_crtc *crtc)
 {
 	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
@@ -265,6 +311,17 @@ intel_reference_shared_dpll(struct intel_shared_dpll *pll,
 	shared_dpll[pll->id].crtc_mask |= 1 << crtc->pipe;
 }
 
+/**
+ * intel_shared_dpll_swap_state - make atomic DPLL configuration effective
+ * @state: atomic state
+ *
+ * This is the dpll version of drm_atomic_helper_swap_state() since the
+ * helper does not handle driver-specific global state.
+ *
+ * For consistency with atomic helpers this function does a complete swap,
+ * i.e. it also puts the current state into @state, even though there is no
+ * need for that at this moment.
+ */
 void intel_shared_dpll_swap_state(struct drm_atomic_state *state)
 {
 	struct drm_i915_private *dev_priv = to_i915(state->dev);
@@ -1860,6 +1917,12 @@ static const struct intel_dpll_mgr bxt_pll_mgr = {
 	.get_dpll = bxt_get_dpll,
 };
 
+/**
+ * intel_shared_dpll_init - Initialize shared DPLLs
+ * @dev: drm device
+ *
+ * Initialize shared DPLLs for @dev.
+ */
 void intel_shared_dpll_init(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = to_i915(dev);
@@ -1903,6 +1966,21 @@ void intel_shared_dpll_init(struct drm_device *dev)
 		intel_ddi_pll_init(dev);
 }
 
+/**
+ * intel_get_shared_dpll - get a shared DPLL for CRTC and encoder combination
+ * @crtc: CRTC
+ * @crtc_state: atomic state for @crtc
+ * @encoder: encoder
+ *
+ * Find an appropriate DPLL for the given CRTC and encoder combination. A
+ * reference from the @crtc to the returned pll is registered in the atomic
+ * state. That configuration is made effective by calling
+ * intel_shared_dpll_swap_state(). The reference should be released by calling
+ * intel_release_shared_dpll().
+ *
+ * Returns:
+ * A shared DPLL to be used by @crtc and @encoder with the given @crtc_state.
+ */
 struct intel_shared_dpll *
 intel_get_shared_dpll(struct intel_crtc *crtc,
 		      struct intel_crtc_state *crtc_state,
@@ -1923,6 +2001,9 @@ intel_get_shared_dpll(struct intel_crtc *crtc,
  * @crtc: crtc
  * @state: atomic state
  *
+ * This function releases the reference from @crtc to @dpll from the
+ * atomic @state. The new configuration is made effective by calling
+ * intel_shared_dpll_swap_state().
  */
 void intel_release_shared_dpll(struct intel_shared_dpll *dpll,
 			       struct intel_crtc *crtc,
diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.h b/drivers/gpu/drm/i915/intel_dpll_mgr.h
index e263f74e6964..db96eea00298 100644
--- a/drivers/gpu/drm/i915/intel_dpll_mgr.h
+++ b/drivers/gpu/drm/i915/intel_dpll_mgr.h
@@ -40,32 +40,72 @@ struct intel_encoder;
 struct intel_shared_dpll;
 struct intel_dpll_mgr;
 
+/**
+ * enum intel_dpll_id - possible DPLL ids
+ *
+ * Enumeration of possible IDs for a DPLL. Real shared dpll ids must be >= 0.
+ */
 enum intel_dpll_id {
-	DPLL_ID_PRIVATE = -1, /* non-shared dpll in use */
-	/* real shared dpll ids must be >= 0 */
+	/**
+	 * @DPLL_ID_PRIVATE: non-shared dpll in use
+	 */
+	DPLL_ID_PRIVATE = -1,
+
+	/**
+	 * @DPLL_ID_PCH_PLL_A: DPLL A in ILK, SNB and IVB
+	 */
 	DPLL_ID_PCH_PLL_A = 0,
+	/**
+	 * @DPLL_ID_PCH_PLL_B: DPLL B in ILK, SNB and IVB
+	 */
 	DPLL_ID_PCH_PLL_B = 1,
-	/* hsw/bdw */
+
+
+	/**
+	 * @DPLL_ID_WRPLL1: HSW and BDW WRPLL1
+	 */
 	DPLL_ID_WRPLL1 = 0,
+	/**
+	 * @DPLL_ID_WRPLL2: HSW and BDW WRPLL2
+	 */
 	DPLL_ID_WRPLL2 = 1,
+	/**
+	 * @DPLL_ID_SPLL: HSW and BDW SPLL
+	 */
 	DPLL_ID_SPLL = 2,
+	/**
+	 * @DPLL_ID_LCPLL_810: HSW and BDW 0.81 GHz LCPLL
+	 */
 	DPLL_ID_LCPLL_810 = 3,
+	/**
+	 * @DPLL_ID_LCPLL_1350: HSW and BDW 1.35 GHz LCPLL
+	 */
 	DPLL_ID_LCPLL_1350 = 4,
+	/**
+	 * @DPLL_ID_LCPLL_2700: HSW and BDW 2.7 GHz LCPLL
+	 */
 	DPLL_ID_LCPLL_2700 = 5,
 
-	/* skl */
+
+	/**
+	 * @DPLL_ID_SKL_DPLL0: SKL and later DPLL0
+	 */
 	DPLL_ID_SKL_DPLL0 = 0,
+	/**
+	 * @DPLL_ID_SKL_DPLL1: SKL and later DPLL1
+	 */
 	DPLL_ID_SKL_DPLL1 = 1,
+	/**
+	 * @DPLL_ID_SKL_DPLL2: SKL and later DPLL2
+	 */
 	DPLL_ID_SKL_DPLL2 = 2,
+	/**
+	 * @DPLL_ID_SKL_DPLL3: SKL and later DPLL3
+	 */
 	DPLL_ID_SKL_DPLL3 = 3,
 };
 #define I915_NUM_PLLS 6
 
-/** Inform the state checker that the DPLL is kept enabled even if not
- * in use by any crtc.
- */
-#define INTEL_DPLL_ALWAYS_ON	(1 << 0)
-
 struct intel_dpll_hw_state {
 	/* i9xx, pch plls */
 	uint32_t dpll;
@@ -93,36 +133,120 @@ struct intel_dpll_hw_state {
 		 pcsdw12;
 };
 
+/**
+ * struct intel_shared_dpll_state - hold the DPLL atomic state
+ *
+ * This structure holds an atomic state for the DPLL, that can represent
+ * either its current state (in struct &intel_shared_dpll) or a desired
+ * future state which would be applied by an atomic mode set (stored in
+ * a struct &intel_atomic_state).
+ *
+ * See also intel_get_shared_dpll() and intel_release_shared_dpll().
+ */
 struct intel_shared_dpll_state {
-	unsigned crtc_mask; /* mask of CRTCs sharing this PLL */
+	/**
+	 * @crtc_mask: mask of CRTC using this DPLL, active or not
+	 */
+	unsigned crtc_mask;
+
+	/**
+	 * @hw_state: hardware configuration for the DPLL stored in
+	 * struct &intel_dpll_hw_state.
+	 */
 	struct intel_dpll_hw_state hw_state;
 };
 
+/**
+ * struct intel_shared_dpll_funcs - platform specific hooks for managing DPLLs
+ */
 struct intel_shared_dpll_funcs {
-	/* The mode_set hook is optional and should be used together with the
-	 * intel_prepare_shared_dpll function. */
+	/**
+	 * @prepare:
+	 *
+	 * Optional hook to perform operations prior to enabling the PLL.
+	 * Called from intel_prepare_shared_dpll() function unless the PLL
+	 * is already enabled.
+	 */
 	void (*prepare)(struct drm_i915_private *dev_priv,
 			struct intel_shared_dpll *pll);
+
+	/**
+	 * @enable:
+	 *
+	 * Hook for enabling the pll, called from intel_enable_shared_dpll()
+	 * if the pll is not already enabled.
+	 */
 	void (*enable)(struct drm_i915_private *dev_priv,
 		       struct intel_shared_dpll *pll);
+
+	/**
+	 * @disable:
+	 *
+	 * Hook for disabling the pll, called from intel_disable_shared_dpll()
+	 * only when it is safe to disable the pll, i.e., there are no more
+	 * tracked users for it.
+	 */
 	void (*disable)(struct drm_i915_private *dev_priv,
 			struct intel_shared_dpll *pll);
+
+	/**
+	 * @get_hw_state:
+	 *
+	 * Hook for reading the values currently programmed to the DPLL
+	 * registers. This is used for initial hw state readout and state
+	 * verification after a mode set.
+	 */
 	bool (*get_hw_state)(struct drm_i915_private *dev_priv,
 			     struct intel_shared_dpll *pll,
 			     struct intel_dpll_hw_state *hw_state);
 };
 
+/**
+ * struct intel_shared_dpll - display PLL with tracked state and users
+ */
 struct intel_shared_dpll {
+	/**
+	 * @state:
+	 *
+	 * Store the state for the pll, including the its hw state
+	 * and CRTCs using it.
+	 */
 	struct intel_shared_dpll_state state;
 
-	unsigned active_mask; /* mask of active CRTCs (i.e. DPMS on) */
-	bool on; /* is the PLL actually active? Disabled during modeset */
+	/**
+	 * @active_mask: mask of active CRTCs (i.e. DPMS on) using this DPLL
+	 */
+	unsigned active_mask;
+
+	/**
+	 * @on: is the PLL actually active? Disabled during modeset
+	 */
+	bool on;
+
+	/**
+	 * @name: DPLL name; used for logging
+	 */
 	const char *name;
-	/* should match the index in the dev_priv->shared_dplls array */
+
+	/**
+	 * @id: unique indentifier for this DPLL; should match the index in the
+	 * dev_priv->shared_dplls array
+	 */
 	enum intel_dpll_id id;
 
+	/**
+	 * @funcs: platform specific hooks
+	 */
 	struct intel_shared_dpll_funcs funcs;
 
+#define INTEL_DPLL_ALWAYS_ON	(1 << 0)
+	/**
+	 * @flags:
+	 *
+	 * INTEL_DPLL_ALWAYS_ON
+	 *     Inform the state checker that the DPLL is kept enabled even if
+	 *     not in use by any CRTC.
+	 */
 	uint32_t flags;
 };