[PATCH v2] imx-drm: imx-drm-core: add suspend/resume support

[shawn.guo@freescale.com (Shawn Guo)]

HDMI currently stops working after a system suspend/resume cycle.  The
cause is that the mode setting states in hardware gets lost and isn't
restored across the suspend/resume cycle.

The patch adds a very basic suspend/resume support to imx-drm driver,
and calls drm_helper_resume_force_mode() in .resume hook to restore the
mode setting states, so that HDMI can continue working after a system
suspend/resume cycle.

Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
---
Changs since v1:
 - Do not walk through connector->funcs->dpms() but only call
   drm_helper_resume_force_mode() in .resume.

 drivers/staging/imx-drm/imx-drm-core.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/staging/imx-drm/imx-drm-core.c b/drivers/staging/imx-drm/imx-drm-core.c
index def8280d7ee6..ab41152089a3 100644
--- a/drivers/staging/imx-drm/imx-drm-core.c
+++ b/drivers/staging/imx-drm/imx-drm-core.c
@@ -696,6 +696,29 @@ static int imx_drm_platform_remove(struct platform_device *pdev)
 	return 0;
 }
 
+#ifdef CONFIG_PM_SLEEP
+static int imx_drm_suspend(struct device *dev)
+{
+	struct drm_device *drm_dev = dev_get_drvdata(dev);
+
+	drm_kms_helper_poll_disable(drm_dev);
+
+	return 0;
+}
+
+static int imx_drm_resume(struct device *dev)
+{
+	struct drm_device *drm_dev = dev_get_drvdata(dev);
+
+	drm_helper_resume_force_mode(drm_dev);
+	drm_kms_helper_poll_enable(drm_dev);
+
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(imx_drm_pm_ops, imx_drm_suspend, imx_drm_resume);
+
 static const struct of_device_id imx_drm_dt_ids[] = {
 	{ .compatible = "fsl,imx-display-subsystem", },
 	{ /* sentinel */ },
@@ -708,6 +731,7 @@ static struct platform_driver imx_drm_pdrv = {
 	.driver		= {
 		.owner	= THIS_MODULE,
 		.name	= "imx-drm",
+		.pm	= &imx_drm_pm_ops,
 		.of_match_table = imx_drm_dt_ids,
 	},
 };
-- 
1.9.1