drm/radeon: rework pll selection (v4)

For DP we can use the same PPLL for all active DP
encoders.  Take advantage of that to prevent cases
where we may end up sharing a PPLL between DP and
non-DP which won't work.  Also clean up the code
a bit.

v2: - fix missing pll_id assignment in crtc init
v3: - fix DP PPLL check
    - document functions
    - break in main encoder search loop after matching.
      no need to keep checking additional encoders.
v4: - same as v3, but re-apply to drm-next as the corner
      cases are fixed properly in subsequent patches.

fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=54471

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/atombios_crtc.c

@@ -1482,14 +1482,98 @@ static void radeon_legacy_atom_fixup(struct drm_crtc *crtc)
 	}
 }
 
+/**
+ * radeon_get_pll_use_mask - look up a mask of which pplls are in use
+ *
+ * @crtc: drm crtc
+ *
+ * Returns the mask of which PPLLs (Pixel PLLs) are in use.
+ */
+static u32 radeon_get_pll_use_mask(struct drm_crtc *crtc)
+{
+	struct drm_device *dev = crtc->dev;
+	struct drm_crtc *test_crtc;
+	struct radeon_crtc *radeon_test_crtc;
+	u32 pll_in_use = 0;
+
+	list_for_each_entry(test_crtc, &dev->mode_config.crtc_list, head) {
+		if (crtc == test_crtc)
+			continue;
+
+		radeon_test_crtc = to_radeon_crtc(test_crtc);
+		if (radeon_test_crtc->pll_id != ATOM_PPLL_INVALID)
+			pll_in_use |= (1 << radeon_test_crtc->pll_id);
+	}
+	return pll_in_use;
+}
+
+/**
+ * radeon_get_shared_dp_ppll - return the PPLL used by another crtc for DP
+ *
+ * @crtc: drm crtc
+ *
+ * Returns the PPLL (Pixel PLL) used by another crtc/encoder which is
+ * also in DP mode.  For DP, a single PPLL can be used for all DP
+ * crtcs/encoders.
+ */
+static int radeon_get_shared_dp_ppll(struct drm_crtc *crtc)
+{
+	struct drm_device *dev = crtc->dev;
+	struct drm_encoder *test_encoder;
+	struct radeon_crtc *radeon_test_crtc;
+
+	list_for_each_entry(test_encoder, &dev->mode_config.encoder_list, head) {
+		if (test_encoder->crtc && (test_encoder->crtc != crtc)) {
+			if (ENCODER_MODE_IS_DP(atombios_get_encoder_mode(test_encoder))) {
+				/* for DP use the same PLL for all */
+				radeon_test_crtc = to_radeon_crtc(test_encoder->crtc);
+				if (radeon_test_crtc->pll_id != ATOM_PPLL_INVALID)
+					return radeon_test_crtc->pll_id;
+			}
+		}
+	}
+	return ATOM_PPLL_INVALID;
+}
+
+/**
+ * radeon_atom_pick_pll - Allocate a PPLL for use by the crtc.
+ *
+ * @crtc: drm crtc
+ *
+ * Returns the PPLL (Pixel PLL) to be used by the crtc.  For DP monitors
+ * a single PPLL can be used for all DP crtcs/encoders.  For non-DP
+ * monitors a dedicated PPLL must be used.  If a particular board has
+ * an external DP PLL, return ATOM_PPLL_INVALID to skip PLL programming
+ * as there is no need to program the PLL itself.  If we are not able to
+ * allocate a PLL, return ATOM_PPLL_INVALID to skip PLL programming to
+ * avoid messing up an existing monitor.
+ *
+ * Asic specific PLL information
+ *
+ * DCE 6.1
+ * - PPLL2 is only available to UNIPHYA (both DP and non-DP)
+ * - PPLL0, PPLL1 are available for UNIPHYB/C/D/E/F (both DP and non-DP)
+ *
+ * DCE 6.0
+ * - PPLL0 is available to all UNIPHY (DP only)
+ * - PPLL1, PPLL2 are available for all UNIPHY (both DP and non-DP) and DAC
+ *
+ * DCE 5.0
+ * - DCPLL is available to all UNIPHY (DP only)
+ * - PPLL1, PPLL2 are available for all UNIPHY (both DP and non-DP) and DAC
+ *
+ * DCE 3.0/4.0/4.1
+ * - PPLL1, PPLL2 are available for all UNIPHY (both DP and non-DP) and DAC
+ *
+ */
 static int radeon_atom_pick_pll(struct drm_crtc *crtc)
 {
 	struct radeon_crtc *radeon_crtc = to_radeon_crtc(crtc);
 	struct drm_device *dev = crtc->dev;
 	struct radeon_device *rdev = dev->dev_private;
 	struct drm_encoder *test_encoder;
-	struct drm_crtc *test_crtc;
-	uint32_t pll_in_use = 0;
+	u32 pll_in_use;
+	int pll;
 
 	if (ASIC_IS_DCE61(rdev)) {
 		list_for_each_entry(test_encoder, &dev->mode_config.encoder_list, head) {
@@ -1501,64 +1585,75 @@ static int radeon_atom_pick_pll(struct drm_crtc *crtc)
 
 				if ((test_radeon_encoder->encoder_id ==
 				     ENCODER_OBJECT_ID_INTERNAL_UNIPHY) &&
-				    (dig->linkb == false)) /* UNIPHY A uses PPLL2 */
+				    (dig->linkb == false))
+					/* UNIPHY A uses PPLL2 */
 					return ATOM_PPLL2;
+				else if (ENCODER_MODE_IS_DP(atombios_get_encoder_mode(test_encoder))) {
+					/* UNIPHY B/C/D/E/F */
+					if (rdev->clock.dp_extclk)
+						/* skip PPLL programming if using ext clock */
+						return ATOM_PPLL_INVALID;
+					else {
+						/* use the same PPLL for all DP monitors */
+						pll = radeon_get_shared_dp_ppll(crtc);
+						if (pll != ATOM_PPLL_INVALID)
+							return pll;
+					}
+				}
+				break;
 			}
 		}
 		/* UNIPHY B/C/D/E/F */
-		list_for_each_entry(test_crtc, &dev->mode_config.crtc_list, head) {
-			struct radeon_crtc *radeon_test_crtc;
-
-			if (crtc == test_crtc)
-				continue;
-
-			radeon_test_crtc = to_radeon_crtc(test_crtc);
-			if ((radeon_test_crtc->pll_id == ATOM_PPLL0) ||
-			    (radeon_test_crtc->pll_id == ATOM_PPLL1))
-				pll_in_use |= (1 << radeon_test_crtc->pll_id);
-		}
-		if (!(pll_in_use & 4))
+		pll_in_use = radeon_get_pll_use_mask(crtc);
+		if (!(pll_in_use & (1 << ATOM_PPLL0)))
 			return ATOM_PPLL0;
-		return ATOM_PPLL1;
+		if (!(pll_in_use & (1 << ATOM_PPLL1)))
+			return ATOM_PPLL1;
+		DRM_ERROR("unable to allocate a PPLL\n");
+		return ATOM_PPLL_INVALID;
 	} else if (ASIC_IS_DCE4(rdev)) {
 		list_for_each_entry(test_encoder, &dev->mode_config.encoder_list, head) {
 			if (test_encoder->crtc && (test_encoder->crtc == crtc)) {
 				/* in DP mode, the DP ref clock can come from PPLL, DCPLL, or ext clock,
 				 * depending on the asic:
 				 * DCE4: PPLL or ext clock
-				 * DCE5: DCPLL or ext clock
+				 * DCE5: PPLL, DCPLL, or ext clock
+				 * DCE6: PPLL, PPLL0, or ext clock
 				 *
 				 * Setting ATOM_PPLL_INVALID will cause SetPixelClock to skip
 				 * PPLL/DCPLL programming and only program the DP DTO for the
 				 * crtc virtual pixel clock.
 				 */
 				if (ENCODER_MODE_IS_DP(atombios_get_encoder_mode(test_encoder))) {
 					if (rdev->clock.dp_extclk)
+						/* skip PPLL programming if using ext clock */
 						return ATOM_PPLL_INVALID;
 					else if (ASIC_IS_DCE6(rdev))
+						/* use PPLL0 for all DP */
 						return ATOM_PPLL0;
 					else if (ASIC_IS_DCE5(rdev))
+						/* use DCPLL for all DP */
 						return ATOM_DCPLL;
+					else {
+						/* use the same PPLL for all DP monitors */
+						pll = radeon_get_shared_dp_ppll(crtc);
+						if (pll != ATOM_PPLL_INVALID)
+							return pll;
+					}
 				}
+				break;
 			}
 		}
-
-		/* otherwise, pick one of the plls */
-		list_for_each_entry(test_crtc, &dev->mode_config.crtc_list, head) {
-			struct radeon_crtc *radeon_test_crtc;
-
-			if (crtc == test_crtc)
-				continue;
-
-			radeon_test_crtc = to_radeon_crtc(test_crtc);
-			if ((radeon_test_crtc->pll_id >= ATOM_PPLL1) &&
-			    (radeon_test_crtc->pll_id <= ATOM_PPLL2))
-				pll_in_use |= (1 << radeon_test_crtc->pll_id);
-		}
-		if (!(pll_in_use & 1))
+		/* all other cases */
+		pll_in_use = radeon_get_pll_use_mask(crtc);
+		if (!(pll_in_use & (1 << ATOM_PPLL2)))
+			return ATOM_PPLL2;
+		if (!(pll_in_use & (1 << ATOM_PPLL1)))
 			return ATOM_PPLL1;
-		return ATOM_PPLL2;
+		DRM_ERROR("unable to allocate a PPLL\n");
+		return ATOM_PPLL_INVALID;
 	} else
+		/* use PPLL1 or PPLL2 */
 		return radeon_crtc->crtc_id;
 
 }
@@ -1700,7 +1795,7 @@ static void atombios_crtc_disable(struct drm_crtc *crtc)
 		break;
 	}
 done:
-	radeon_crtc->pll_id = -1;
+	radeon_crtc->pll_id = ATOM_PPLL_INVALID;
 }
 
 static const struct drm_crtc_helper_funcs atombios_helper_funcs = {
@@ -1749,6 +1844,6 @@ void radeon_atombios_init_crtc(struct drm_device *dev,
 		else
 			radeon_crtc->crtc_offset = 0;
 	}
-	radeon_crtc->pll_id = -1;
+	radeon_crtc->pll_id = ATOM_PPLL_INVALID;
 	drm_crtc_helper_add(&radeon_crtc->base, &atombios_helper_funcs);
 }