[PATCH v6 2/3] drm/i915: Lookup and attach ACPI device node for connectors

[Rajat Jain <rajatja@google.com>]

Lookup and attach ACPI nodes for intel connectors. The lookup is done
in compliance with ACPI Spec 6.3
https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf
(Ref: Pages 1119 - 1123).

This can be useful for any connector specific platform properties. (This
will be used for privacy screen in next patch).

Signed-off-by: Rajat Jain <rajatja@google.com>
---
v6: Addressed minor comments from Jani at
    https://lkml.org/lkml/2020/1/24/1143
     - local variable renamed.
     - used drm_dbg_kms()
     - used acpi_device_handle()
     - Used opaque type acpi_handle instead of void*
v5: same as v4
v4: Same as v3
v3: fold the code into existing acpi_device_id_update() function
v2: formed by splitting the original patch into ACPI lookup, and privacy
    screen property. Also move it into i915 now that I found existing code
    in i915 that can be re-used.

 drivers/gpu/drm/i915/display/intel_acpi.c     | 24 +++++++++++++++++++
 .../drm/i915/display/intel_display_types.h    |  5 ++++
 drivers/gpu/drm/i915/display/intel_dp.c       |  3 +++
 3 files changed, 32 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_acpi.c b/drivers/gpu/drm/i915/display/intel_acpi.c
index 3e6831cca4ac1..870c1ad98df92 100644
--- a/drivers/gpu/drm/i915/display/intel_acpi.c
+++ b/drivers/gpu/drm/i915/display/intel_acpi.c
@@ -222,11 +222,22 @@ static u32 acpi_display_type(struct intel_connector *connector)
 	return display_type;
 }
 
+/*
+ * Ref: ACPI Spec 6.3
+ * https://uefi.org/sites/default/files/resources/ACPI_6_3_final_Jan30.pdf
+ * Pages 1119 - 1123 describe, what I believe, a standard way of
+ * identifying / addressing "display panels" in the ACPI. It provides
+ * a way for the ACPI to define devices for the display panels attached
+ * to the system. It thus provides a way for the BIOS to export any panel
+ * specific properties to the system via ACPI (like device trees).
+ */
 void intel_acpi_device_id_update(struct drm_i915_private *dev_priv)
 {
 	struct drm_device *dev = &dev_priv->drm;
 	struct intel_connector *connector;
 	struct drm_connector_list_iter conn_iter;
+	struct acpi_device *conn_dev;
+	u64 conn_addr;
 	u8 display_index[16] = {};
 
 	/* Populate the ACPI IDs for all connectors for a given drm_device */
@@ -242,6 +253,19 @@ void intel_acpi_device_id_update(struct drm_i915_private *dev_priv)
 		device_id |= display_index[type]++ << ACPI_DISPLAY_INDEX_SHIFT;
 
 		connector->acpi_device_id = device_id;
+
+		/* Build the _ADR to look for */
+		conn_addr = device_id | ACPI_DEVICE_ID_SCHEME |
+				ACPI_BIOS_CAN_DETECT;
+
+		drm_dbg_kms(dev, "Checking connector ACPI node at _ADR=%llX\n",
+			    conn_addr);
+
+		/* Look up the connector device, under the PCI device */
+		conn_dev = acpi_find_child_device(
+					ACPI_COMPANION(&dev->pdev->dev),
+					conn_addr, false);
+		connector->acpi_handle = acpi_device_handle(conn_dev);
 	}
 	drm_connector_list_iter_end(&conn_iter);
 }
diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 5e00e611f077f..d70612cc1ba2a 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -411,9 +411,14 @@ struct intel_connector {
 	 */
 	struct intel_encoder *encoder;
 
+#ifdef CONFIG_ACPI
 	/* ACPI device id for ACPI and driver cooperation */
 	u32 acpi_device_id;
 
+	/* ACPI handle corresponding to this connector display, if found */
+	acpi_handle acpi_handle;
+#endif
+
 	/* Reads out the current hw, returning true if the connector is enabled
 	 * and active (i.e. dpms ON state). */
 	bool (*get_hw_state)(struct intel_connector *);
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 0a417cd2af2bc..171821113d362 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -44,6 +44,7 @@
 #include "i915_debugfs.h"
 #include "i915_drv.h"
 #include "i915_trace.h"
+#include "intel_acpi.h"
 #include "intel_atomic.h"
 #include "intel_audio.h"
 #include "intel_connector.h"
@@ -6868,6 +6869,8 @@ intel_dp_add_properties(struct intel_dp *intel_dp, struct drm_connector *connect
 
 		connector->state->scaling_mode = DRM_MODE_SCALE_ASPECT;
 
+		/* Lookup the ACPI node corresponding to the connector */
+		intel_acpi_device_id_update(dev_priv);
 	}
 }
 
-- 
2.25.0.265.gbab2e86ba0-goog