imx-drm: imx-drm-core: add basic suspend/resume support

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.

Since the suspend/resume hook can be called with drm_device pointer
being NULL from driver data, we need a check on the pointer in the
hooks.  And to avoid using a stale pointer from driver data, it also
clears driver data in .unload hook.

Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/imx-drm/imx-drm-core.c b/drivers/staging/imx-drm/imx-drm-core.c
index 4289cc8..b188478 100644 (file)
--- a/drivers/staging/imx-drm/imx-drm-core.c
+++ b/drivers/staging/imx-drm/imx-drm-core.c
@@ -87,6 +87,8 @@ static int imx_drm_driver_unload(struct drm_device *drm)
        drm_vblank_cleanup(drm);
        drm_mode_config_cleanup(drm);
 
+       platform_set_drvdata(drm->platformdev, NULL);
+
        return 0;
 }
 
@@ -648,6 +650,36 @@ 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);
+
+       /* The drm_dev is NULL before .load hook is called */
+       if (drm_dev == NULL)
+               return 0;
+
+       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);
+
+       if (drm_dev == NULL)
+               return 0;
+
+       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 */ },
@@ -660,6 +692,7 @@ 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,
        },
 };