drm/tilcdc: Restore old dpms state in pm_resume()

Restore old dpms state in pm_resume(). The dpms is turned off in
pm_suspend() and it should be restored to its original state in
pm_resume(). Without this patch the display is left blanked after a
suspend/resume cycle.

Fixes commit 614b3cfe ("drm/tilcdc: disable the lcd controller/dma
engine when suspend invoked")
Signed-off-by: Jyri Sarha <jsarha@ti.com>

drivers/gpu/drm/tilcdc/tilcdc_crtc.c

@@ -246,6 +246,13 @@ void tilcdc_crtc_dpms(struct drm_crtc *crtc, int mode)
 	}
 }
 
+int tilcdc_crtc_current_dpms_state(struct drm_crtc *crtc)
+{
+	struct tilcdc_crtc *tilcdc_crtc = to_tilcdc_crtc(crtc);
+
+	return tilcdc_crtc->dpms;
+}
+
 static bool tilcdc_crtc_mode_fixup(struct drm_crtc *crtc,
 		const struct drm_display_mode *mode,
 		struct drm_display_mode *adjusted_mode)

drivers/gpu/drm/tilcdc/tilcdc_drv.c

@@ -597,6 +597,7 @@ static int tilcdc_pm_suspend(struct device *dev)
 	}
 
 	/* Disable the LCDC controller, to avoid locking up the PRCM */
+	priv->saved_dpms_state = tilcdc_crtc_current_dpms_state(priv->crtc);
 	tilcdc_crtc_dpms(priv->crtc, DRM_MODE_DPMS_OFF);
 
 	/* Save register state: */
@@ -627,6 +628,8 @@ static int tilcdc_pm_resume(struct device *dev)
 					     priv->saved_register[n++]);
 	}
 
+	tilcdc_crtc_dpms(priv->crtc, priv->saved_dpms_state);
+
 	drm_kms_helper_poll_enable(ddev);
 
 	return 0;

drivers/gpu/drm/tilcdc/tilcdc_drv.h

@@ -67,6 +67,7 @@ struct tilcdc_drm_private {
 
 	/* register contents saved across suspend/resume: */
 	u32 *saved_register;
+	int saved_dpms_state;
 	bool ctx_valid;
 
 #ifdef CONFIG_CPU_FREQ
@@ -172,5 +173,6 @@ void tilcdc_crtc_set_simulate_vesa_sync(struct drm_crtc *crtc,
 int tilcdc_crtc_mode_valid(struct drm_crtc *crtc, struct drm_display_mode *mode);
 int tilcdc_crtc_max_width(struct drm_crtc *crtc);
 void tilcdc_crtc_dpms(struct drm_crtc *crtc, int mode);
+int tilcdc_crtc_current_dpms_state(struct drm_crtc *crtc);
 
 #endif /* __TILCDC_DRV_H__ */