drm/stm: dw_mipi_dsi-stm: add sleep power management

Implements system sleep power management ops.
Signed-off-by: Yannick Fertré <yannick.fertre@st.com>
Acked-by: Philippe Cornu <philippe.cornu@st.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1553156033-13792-1-git-send-email-yannick.fertre@st.com

drivers/gpu/drm/stm/dw_mipi_dsi-stm.c

@@ -356,12 +356,40 @@ static int dw_mipi_dsi_stm_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static int __maybe_unused dw_mipi_dsi_stm_suspend(struct device *dev)
+{
+	struct dw_mipi_dsi_stm *dsi = dw_mipi_dsi_stm_plat_data.priv_data;
+
+	DRM_DEBUG_DRIVER("\n");
+
+	clk_disable_unprepare(dsi->pllref_clk);
+
+	return 0;
+}
+
+static int __maybe_unused dw_mipi_dsi_stm_resume(struct device *dev)
+{
+	struct dw_mipi_dsi_stm *dsi = dw_mipi_dsi_stm_plat_data.priv_data;
+
+	DRM_DEBUG_DRIVER("\n");
+
+	clk_prepare_enable(dsi->pllref_clk);
+
+	return 0;
+}
+
+static const struct dev_pm_ops dw_mipi_dsi_stm_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(dw_mipi_dsi_stm_suspend,
+				dw_mipi_dsi_stm_resume)
+};
+
 static struct platform_driver dw_mipi_dsi_stm_driver = {
 	.probe		= dw_mipi_dsi_stm_probe,
 	.remove		= dw_mipi_dsi_stm_remove,
 	.driver		= {
 		.of_match_table = dw_mipi_dsi_stm_dt_ids,
 		.name	= "stm32-display-dsi",
+		.pm = &dw_mipi_dsi_stm_pm_ops,
 	},
 };