[PATCH] drm/i915/ehl: Allow combo PHY A to drive a third external display

[Matt Roper <matthew.d.roper@intel.com>]

EHL has a mux on combo PHY A that allows it to be driven either by an
internal display (using DDI-A or DSI DPHY) or by an external display
(using DDI-D).  This is a motherboard design decision that can not be
changed on the fly.  Let's use the VBT child device settings to try to
figure out our board's configuration and program the mux accordingly.

Cc: Clint Taylor <Clinton.A.Taylor@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h        |  1 +
 drivers/gpu/drm/i915/intel_bios.c      | 24 ++++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_bios.h      |  1 +
 drivers/gpu/drm/i915/intel_combo_phy.c | 13 +++++++++++++
 4 files changed, 39 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 368ee717580c..0ae0d85304b5 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -11121,6 +11121,7 @@ enum skl_power_gate {
 #define _ICL_PHY_MISC_B		0x64C04
 #define ICL_PHY_MISC(port)	_MMIO_PORT(port, _ICL_PHY_MISC_A, \
 						 _ICL_PHY_MISC_B)
+#define  ICL_PHY_MISC_MUX_DDID			(1 << 28)
 #define  ICL_PHY_MISC_DE_IO_COMP_PWR_DOWN	(1 << 23)
 
 /* Icelake Display Stream Compression Registers */
diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index d3d473934ea4..ac861852e843 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -1667,6 +1667,9 @@ parse_general_definitions(struct drm_i915_private *dev_priv,
 		if (!child->device_type)
 			continue;
 
+		DRM_DEBUG_KMS("Found VBT child device with type 0x%x\n",
+			      child->device_type);
+
 		/*
 		 * Copy as much as we know (sizeof) and is available
 		 * (child_dev_size) of the child device. Accessing the data must
@@ -2259,3 +2262,24 @@ enum aux_ch intel_bios_port_aux_ch(struct drm_i915_private *dev_priv,
 
 	return aux_ch;
 }
+
+/**
+ * intel_bios_has_internal_display - are any child devices marked 'internal?'
+ * @dev_priv:	i915 device instance
+ *
+ * Returns true if any of the child devices have a device type containing
+ * the %DEVICE_TYPE_INTERNAL_CONNECTOR bit.
+ */
+bool intel_bios_has_internal_display(struct drm_i915_private *dev_priv)
+{
+	int i;
+
+	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
+		struct child_device_config *child = &dev_priv->vbt.child_dev[i];
+
+		if (child->device_type & DEVICE_TYPE_INTERNAL_CONNECTOR)
+			return true;
+	}
+
+	return false;
+}
diff --git a/drivers/gpu/drm/i915/intel_bios.h b/drivers/gpu/drm/i915/intel_bios.h
index 4e42cfaf61a7..df822a1efe55 100644
--- a/drivers/gpu/drm/i915/intel_bios.h
+++ b/drivers/gpu/drm/i915/intel_bios.h
@@ -240,5 +240,6 @@ bool intel_bios_is_port_hpd_inverted(const struct drm_i915_private *i915,
 bool intel_bios_is_lspcon_present(const struct drm_i915_private *i915,
 				  enum port port);
 enum aux_ch intel_bios_port_aux_ch(struct drm_i915_private *dev_priv, enum port port);
+bool intel_bios_has_internal_display(struct drm_i915_private *dev_priv);
 
 #endif /* _INTEL_BIOS_H_ */
diff --git a/drivers/gpu/drm/i915/intel_combo_phy.c b/drivers/gpu/drm/i915/intel_combo_phy.c
index 841708da5a56..3bf3e41c5296 100644
--- a/drivers/gpu/drm/i915/intel_combo_phy.c
+++ b/drivers/gpu/drm/i915/intel_combo_phy.c
@@ -273,7 +273,20 @@ static void icl_combo_phys_init(struct drm_i915_private *dev_priv)
 			continue;
 		}
 
+		/*
+		 * EHL's combo PHY A can be hooked up to either an external
+		 * display (via DDI-D) or an internal display (via DDI-A or
+		 * the DSI DPHY).  This is a motherboard design decision that
+		 * can't be changed on the fly, so initialize the PHY's mux
+		 * based on whether our VBT indicates the presence of any
+		 * "internal" child devices.
+		 */
 		val = I915_READ(ICL_PHY_MISC(port));
+		if (!IS_ICELAKE(dev_priv) && port == PORT_A &&
+		    !intel_bios_has_internal_display(dev_priv))
+			val |= ICL_PHY_MISC_MUX_DDID;
+		else
+			val &= ~ICL_PHY_MISC_MUX_DDID;
 		val &= ~ICL_PHY_MISC_DE_IO_COMP_PWR_DOWN;
 		I915_WRITE(ICL_PHY_MISC(port), val);
 
-- 
2.14.5

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