drm/ast: astdp: Wake up during connector status detection

Power up the ASTDP connector for connection status detection if the
connector is not active. Keep it powered if a display is attached.

This fixes a bug where the connector does not come back after
disconnecting the display. The encoder's atomic_disable turns off
power on the physical connector. Further HPD reads will fail,
thus preventing the driver from detecting re-connected displays.

For connectors that are actively used, only test the HPD flag without
touching power.

Fixes: f81bb0ac ("drm/ast: report connection status on Display Port.")
Cc: Jocelyn Falempe <jfalempe@redhat.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Dave Airlie <airlied@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v6.6+
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240717143319.104012-2-tzimmermann@suse.de

drivers/gpu/drm/ast/ast_dp.c

@@ -158,7 +158,14 @@ void ast_dp_launch(struct drm_device *dev)
 			       ASTDP_HOST_EDID_READ_DONE);
 }
 
+bool ast_dp_power_is_on(struct ast_device *ast)
+{
+	u8 vgacre3;
+
+	vgacre3 = ast_get_index_reg(ast, AST_IO_VGACRI, 0xe3);
 
+	return !(vgacre3 & AST_DP_PHY_SLEEP);
+}
 
 void ast_dp_power_on_off(struct drm_device *dev, bool on)
 {

drivers/gpu/drm/ast/ast_drv.h

@@ -472,6 +472,7 @@ void ast_init_3rdtx(struct drm_device *dev);
 bool ast_astdp_is_connected(struct ast_device *ast);
 int ast_astdp_read_edid(struct drm_device *dev, u8 *ediddata);
 void ast_dp_launch(struct drm_device *dev);
+bool ast_dp_power_is_on(struct ast_device *ast);
 void ast_dp_power_on_off(struct drm_device *dev, bool no);
 void ast_dp_set_on_off(struct drm_device *dev, bool no);
 void ast_dp_set_mode(struct drm_crtc *crtc, struct ast_vbios_mode_info *vbios_mode);

drivers/gpu/drm/ast/ast_mode.c

@@ -28,6 +28,7 @@
  * Authors: Dave Airlie <airlied@redhat.com>
  */
 
+#include <linux/delay.h>
 #include <linux/export.h>
 #include <linux/pci.h>
 
@@ -1687,11 +1688,35 @@ static int ast_astdp_connector_helper_detect_ctx(struct drm_connector *connector
 						 struct drm_modeset_acquire_ctx *ctx,
 						 bool force)
 {
+	struct drm_device *dev = connector->dev;
 	struct ast_device *ast = to_ast_device(connector->dev);
+	enum drm_connector_status status = connector_status_disconnected;
+	struct drm_connector_state *connector_state = connector->state;
+	bool is_active = false;
+
+	mutex_lock(&ast->modeset_lock);
+
+	if (connector_state && connector_state->crtc) {
+		struct drm_crtc_state *crtc_state = connector_state->crtc->state;
+
+		if (crtc_state && crtc_state->active)
+			is_active = true;
+	}
+
+	if (!is_active && !ast_dp_power_is_on(ast)) {
+		ast_dp_power_on_off(dev, true);
+		msleep(50);
+	}
 
 	if (ast_astdp_is_connected(ast))
-		return connector_status_connected;
-	return connector_status_disconnected;
+		status = connector_status_connected;
+
+	if (!is_active && status == connector_status_disconnected)
+		ast_dp_power_on_off(dev, false);
+
+	mutex_unlock(&ast->modeset_lock);
+
+	return status;
 }
 
 static const struct drm_connector_helper_funcs ast_astdp_connector_helper_funcs = {