drm/rockchip: dw_hdmi: Handle suspend/resume

On Rockchip rk3288-based Chromebooks when you do a suspend/resume
cycle:

1. You lose the ability to detect an HDMI device being plugged in.

2. If you're using the i2c bus built in to dw_hdmi then it stops
working.

Let's call the core dw-hdmi's suspend/resume functions to restore
things.

NOTE: in downstream Chrome OS (based on kernel 3.14) we used the
"late/early" versions of suspend/resume because we found that the VOP
was sometimes resuming before dw_hdmi and then calling into us before
we were fully resumed.  For now I have gone back to the normal
suspend/resume because I can't reproduce the problems.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190604204207.168085-2-dianders@chromium.org

drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c

@@ -542,11 +542,25 @@ static int dw_hdmi_rockchip_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static int __maybe_unused dw_hdmi_rockchip_resume(struct device *dev)
+{
+	struct rockchip_hdmi *hdmi = dev_get_drvdata(dev);
+
+	dw_hdmi_resume(hdmi->hdmi);
+
+	return 0;
+}
+
+static const struct dev_pm_ops dw_hdmi_rockchip_pm = {
+	SET_SYSTEM_SLEEP_PM_OPS(NULL, dw_hdmi_rockchip_resume)
+};
+
 struct platform_driver dw_hdmi_rockchip_pltfm_driver = {
 	.probe  = dw_hdmi_rockchip_probe,
 	.remove = dw_hdmi_rockchip_remove,
 	.driver = {
 		.name = "dwhdmi-rockchip",
+		.pm = &dw_hdmi_rockchip_pm,
 		.of_match_table = dw_hdmi_rockchip_dt_ids,
 	},
 };