drm: atmel-hlcdc: Add PM suspend/resume support

On suspend: switch off CRTC if not already suspended with runtime PM

On resume: switch on CRTC if we were not already suspended from runtime
PM while suspending.
Signed-off-by: Sylvain Rochet <sylvain.rochet@finsecur.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c

@@ -561,6 +561,52 @@ static int atmel_hlcdc_dc_drm_remove(struct platform_device *pdev)
 	return 0;
 }
 
+#ifdef CONFIG_PM
+static int atmel_hlcdc_dc_drm_suspend(struct device *dev)
+{
+	struct drm_device *drm_dev = dev_get_drvdata(dev);
+	struct drm_crtc *crtc;
+
+	if (pm_runtime_suspended(dev))
+		return 0;
+
+	drm_modeset_lock_all(drm_dev);
+	list_for_each_entry(crtc, &drm_dev->mode_config.crtc_list, head) {
+		struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
+		if (crtc->enabled) {
+			crtc_funcs->disable(crtc);
+			/* save enable state for resume */
+			crtc->enabled = true;
+		}
+	}
+	drm_modeset_unlock_all(drm_dev);
+	return 0;
+}
+
+static int atmel_hlcdc_dc_drm_resume(struct device *dev)
+{
+	struct drm_device *drm_dev = dev_get_drvdata(dev);
+	struct drm_crtc *crtc;
+
+	if (pm_runtime_suspended(dev))
+		return 0;
+
+	drm_modeset_lock_all(drm_dev);
+	list_for_each_entry(crtc, &drm_dev->mode_config.crtc_list, head) {
+		struct drm_crtc_helper_funcs *crtc_funcs = crtc->helper_private;
+		if (crtc->enabled) {
+			crtc->enabled = false;
+			crtc_funcs->enable(crtc);
+		}
+	}
+	drm_modeset_unlock_all(drm_dev);
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(atmel_hlcdc_dc_drm_pm_ops,
+		atmel_hlcdc_dc_drm_suspend, atmel_hlcdc_dc_drm_resume);
+
 static const struct of_device_id atmel_hlcdc_dc_of_match[] = {
 	{ .compatible = "atmel,hlcdc-display-controller" },
 	{ },
@@ -571,6 +617,7 @@ static struct platform_driver atmel_hlcdc_dc_platform_driver = {
 	.remove	= atmel_hlcdc_dc_drm_remove,
 	.driver	= {
 		.name	= "atmel-hlcdc-display-controller",
+		.pm	= &atmel_hlcdc_dc_drm_pm_ops,
 		.of_match_table = atmel_hlcdc_dc_of_match,
 	},
 };