enqueue.php

<?php function load_parent_theme_css() {
	$parentcss = get_template_directory() . '/style.css';
	wp_enqueue_style(
		'parent-theme',
		get_template_directory_uri() . '/style.css',
		array(),
		filemtime( $parentcss )
	);
}
add_action( 'wp_enqueue_scripts', 'load_parent_theme_css', 11 );