drm/ast: astdp: Move locking into EDID helper

The modeset mutex protects EDID retrival from concurrent modeset
operations. Acquire the lock in ast_astdp_read_edid(). Prepares the
code for conversion to struct drm_edid.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240815151953.184679-4-tzimmermann@suse.de

drivers/gpu/drm/ast/ast_dp.c

@@ -26,6 +26,12 @@ static int ast_astdp_read_edid(struct drm_device *dev, u8 *ediddata)
 	int ret = 0;
 	u8 i;
 
+	/*
+	 * Protect access to I/O registers from concurrent modesetting
+	 * by acquiring the I/O-register lock.
+	 */
+	mutex_lock(&ast->modeset_lock);
+
 	/* Start reading EDID data */
 	ast_set_index_reg_mask(ast, AST_IO_VGACRI, 0xe5, (u8)~AST_IO_VGACRE5_EDID_READ_DONE, 0x00);
 
@@ -95,6 +101,8 @@ static int ast_astdp_read_edid(struct drm_device *dev, u8 *ediddata)
 	ast_set_index_reg_mask(ast, AST_IO_VGACRI, 0xe5, (u8)~AST_IO_VGACRE5_EDID_READ_DONE,
 			       AST_IO_VGACRE5_EDID_READ_DONE);
 
+	mutex_unlock(&ast->modeset_lock);
+
 	return ret;
 }
 
@@ -324,9 +332,6 @@ static const struct drm_encoder_helper_funcs ast_astdp_encoder_helper_funcs = {
 static int ast_astdp_connector_helper_get_modes(struct drm_connector *connector)
 {
 	void *edid;
-	struct drm_device *dev = connector->dev;
-	struct ast_device *ast = to_ast_device(dev);
-
 	int succ;
 	int count;
 
@@ -334,17 +339,9 @@ static int ast_astdp_connector_helper_get_modes(struct drm_connector *connector)
 	if (!edid)
 		goto err_drm_connector_update_edid_property;
 
-	/*
-	 * Protect access to I/O registers from concurrent modesetting
-	 * by acquiring the I/O-register lock.
-	 */
-	mutex_lock(&ast->modeset_lock);
-
 	succ = ast_astdp_read_edid(connector->dev, edid);
 	if (succ < 0)
-		goto err_mutex_unlock;
-
-	mutex_unlock(&ast->modeset_lock);
+		goto err_kfree;
 
 	drm_connector_update_edid_property(connector, edid);
 	count = drm_add_edid_modes(connector, edid);
@@ -352,8 +349,7 @@ static int ast_astdp_connector_helper_get_modes(struct drm_connector *connector)
 
 	return count;
 
-err_mutex_unlock:
-	mutex_unlock(&ast->modeset_lock);
+err_kfree:
 	kfree(edid);
 err_drm_connector_update_edid_property:
 	drm_connector_update_edid_property(connector, NULL);