drm/i915/panel: register drm_panel and call prepare/unprepare for ICL+ DSI

Allocate and register a drm_panel so that drm_panel_followers can find
the panel. Pass the drm_connector::kdev device to drm_panel allocation
for matching. That's only available after drm_sysfs_connector_add(), so
we need to postpone the drm_panel allocation until .late_register()
hook.

The drm_panel framework is moving towards devm_drm_panel_alloc(). It
requires a wrapper struct, and struct intel_panel would be the natural
candidate. However, we can't postpone its allocation until
.late_register(), so we have to use __devm_drm_panel_alloc() directly
for now.

Call the drm_panel_prepare() and drm_panel_unprepare() functions for
ICL+ DSI, so that followers get notified of the panel power state
changes. This can later be expanded to VLV+ DSI and eDP.

Cc: Maxime Ripard <[e-mail]>
Cc: Heikki Krogerus <[e-mail]>
Cc: Lee Shawn C <[e-mail]>
Tested-by: Lee Shawn C <[e-mail]>
Reviewed-by: Maxime Ripard <[e-mail]>
Link: https://lore.kernel.org/r/13d[e-mail]
Signed-off-by: Jani Nikula <[e-mail]>

drivers/gpu/drm/i915/display/icl_dsi.c

···
 	intel_backlight_enable(crtc_state, conn_state);
 	intel_dsi_vbt_exec_sequence(intel_dsi, MIPI_SEQ_BACKLIGHT_ON);
 
+	intel_panel_prepare(crtc_state, conn_state);
+
 	intel_crtc_vblank_on(crtc_state);
 }
 
···
 			      const struct drm_connector_state *old_conn_state)
 {
 	struct intel_dsi *intel_dsi = enc_to_intel_dsi(encoder);
+
+	intel_panel_unprepare(old_conn_state);
 
 	/* step1: turn off backlight */
 	intel_dsi_vbt_exec_sequence(intel_dsi, MIPI_SEQ_BACKLIGHT_OFF);

drivers/gpu/drm/i915/display/intel_display_types.h

···
 #include <drm/drm_crtc.h>
 #include <drm/drm_encoder.h>
 #include <drm/drm_framebuffer.h>
+#include <drm/drm_panel.h>
 #include <drm/drm_rect.h>
 #include <drm/drm_vblank_work.h>
 #include <drm/intel/i915_hdcp_interface.h>
···
 };
 
 struct intel_panel {
+	/* Simple drm_panel */
+	struct drm_panel *base;
+
 	/* Fixed EDID for eDP and LVDS. May hold ERR_PTR for invalid EDID. */
 	const struct drm_edid *fixed_edid;
 

drivers/gpu/drm/i915/display/intel_panel.c

···
 	}
 }
 
+const struct drm_panel_funcs dummy_panel_funcs = {
+};
+
 int intel_panel_register(struct intel_connector *connector)
 {
-	return intel_backlight_device_register(connector);
+	struct intel_display *display = to_intel_display(connector);
+	struct intel_panel *panel = &connector->panel;
+	int ret;
+
+	ret = intel_backlight_device_register(connector);
+	if (ret)
+		return ret;
+
+	if (connector->base.connector_type == DRM_MODE_CONNECTOR_DSI) {
+		struct device *dev = connector->base.kdev;
+		struct drm_panel *base;
+
+		/* Sanity check. */
+		if (drm_WARN_ON(display->drm, !dev))
+			goto out;
+
+		/*
+		 * We need drm_connector::kdev for allocating the panel, to make
+		 * drm_panel_add_follower() lookups work. The kdev is
+		 * initialized in drm_sysfs_connector_add(), just before the
+		 * connector .late_register() hooks. So we can't allocate the
+		 * panel at connector init time, and can't allocate struct
+		 * intel_panel with a drm_panel sub-struct. For now, use
+		 * __devm_drm_panel_alloc() directly.
+		 *
+		 * The lookups also depend on drm_connector::fwnode being set in
+		 * intel_acpi_assign_connector_fwnodes(). However, if that's
+		 * missing, it will gracefully lead to -EPROBE_DEFER in
+		 * drm_panel_add_follower().
+		 */
+		base = __devm_drm_panel_alloc(dev, sizeof(*base), 0,
+					      &dummy_panel_funcs,
+					      connector->base.connector_type);
+		if (IS_ERR(base)) {
+			ret = PTR_ERR(base);
+			goto err;
+		}
+
+		panel->base = base;
+
+		drm_panel_add(panel->base);
+
+		drm_dbg_kms(display->drm, "[CONNECTOR:%d:%s] Registered panel device '%s', has fwnode: %s\n",
+			    connector->base.base.id, connector->base.name,
+			    dev_name(dev), str_yes_no(dev_fwnode(dev)));
+	}
+
+out:
+	return 0;
+
+err:
+	intel_backlight_device_unregister(connector);
+
+	return ret;
 }
 
 void intel_panel_unregister(struct intel_connector *connector)
 {
+	struct intel_panel *panel = &connector->panel;
+
+	if (panel->base)
+		drm_panel_remove(panel->base);
+
 	intel_backlight_device_unregister(connector);
+}
+
+/* Notify followers, if any, about power being up. */
+void intel_panel_prepare(const struct intel_crtc_state *crtc_state,
+			 const struct drm_connector_state *conn_state)
+{
+	struct intel_connector *connector = to_intel_connector(conn_state->connector);
+	struct intel_panel *panel = &connector->panel;
+
+	drm_panel_prepare(panel->base);
+}
+
+/* Notify followers, if any, about power going down. */
+void intel_panel_unprepare(const struct drm_connector_state *old_conn_state)
+{
+	struct intel_connector *connector = to_intel_connector(old_conn_state->connector);
+	struct intel_panel *panel = &connector->panel;
+
+	drm_panel_unprepare(panel->base);
 }

drivers/gpu/drm/i915/display/intel_panel.h

···
 void intel_panel_add_encoder_fixed_mode(struct intel_connector *connector,
 					struct intel_encoder *encoder);
 
+void intel_panel_prepare(const struct intel_crtc_state *crtc_state,
+			 const struct drm_connector_state *conn_state);
+void intel_panel_unprepare(const struct drm_connector_state *old_conn_state);
+
 #endif /* __INTEL_PANEL_H__ */