[PATCH] drm/tilcdc: Recover from sync lost error flood by resetting the LCDC

[Jyri Sarha <jsarha@xxxxxx>]

Recover from sync lost error flood by resetting the LCDC in stead of
turning off the SYNC_LOST error IRQ. When LCDC starves on limited
memory bandwidth it may sometimes result an error situation when the
picture may have shifted couple of pixels to right and SYNC_LOST
interrupt is generated on every frame. LCDC main reset recovers from
this situation and causes a brief blanking on the screen.

Signed-off-by: Jyri Sarha <jsarha@xxxxxx>
---
 drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 34 +++++++++++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
index 051e5e1..5aa86e9 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -46,6 +46,8 @@ struct tilcdc_crtc {
 
 	int sync_lost_count;
 	bool frame_intact;
+	struct workqueue_struct *wq;
+	struct work_struct recover_work;
 };
 #define to_tilcdc_crtc(x) container_of(x, struct tilcdc_crtc, base)
 
@@ -60,6 +62,25 @@ static void unref_worker(struct drm_flip_work *work, void *val)
 	mutex_unlock(&dev->mode_config.mutex);
 }
 
+static void stop(struct drm_crtc *crtc);
+static void start(struct drm_crtc *crtc);
+static void tilcdc_crtc_recover_work(struct work_struct *work)
+{
+	struct tilcdc_crtc *tilcdc_crtc =
+		container_of(work, struct tilcdc_crtc, recover_work);
+	struct drm_crtc *crtc = &tilcdc_crtc->base;
+
+	dev_info(crtc->dev->dev, "%s: Reset CRTC", __func__);
+
+	if (tilcdc_crtc->dpms == DRM_MODE_DPMS_OFF)
+		return;
+
+	drm_modeset_lock_crtc(crtc, NULL);
+	stop(crtc);
+	start(crtc);
+	drm_modeset_unlock_crtc(crtc);
+}
+
 static void set_scanout(struct drm_crtc *crtc, struct drm_framebuffer *fb)
 {
 	struct tilcdc_crtc *tilcdc_crtc = to_tilcdc_crtc(crtc);
@@ -125,6 +146,7 @@ static void tilcdc_crtc_destroy(struct drm_crtc *crtc)
 	tilcdc_crtc_dpms(crtc, DRM_MODE_DPMS_OFF);
 
 	of_node_put(crtc->port);
+	destroy_workqueue(tilcdc_crtc->wq);
 	drm_crtc_cleanup(crtc);
 	drm_flip_work_cleanup(&tilcdc_crtc->unref_work);
 }
@@ -732,10 +754,10 @@ irqreturn_t tilcdc_crtc_irq(struct drm_crtc *crtc)
 		tilcdc_crtc->frame_intact = false;
 		if (tilcdc_crtc->sync_lost_count++ > SYNC_LOST_COUNT_LIMIT) {
 			dev_err(dev->dev,
-				"%s(0x%08x): Sync lost flood detected, disabling the interrupt",
+				"%s(0x%08x): Sync lost flood detected, recovering",
 				__func__, stat);
-			tilcdc_write(dev, LCDC_INT_ENABLE_CLR_REG,
-				     LCDC_SYNC_LOST);
+			queue_work(tilcdc_crtc->wq, &tilcdc_crtc->recover_work);
+			tilcdc_crtc->sync_lost_count = 0;
 		}
 	}
 
@@ -768,6 +790,12 @@ struct drm_crtc *tilcdc_crtc_create(struct drm_device *dev)
 			"unref", unref_worker);
 
 	spin_lock_init(&tilcdc_crtc->irq_lock);
+	tilcdc_crtc->wq = create_singlethread_workqueue("tilcdc/crtc");
+	if (!tilcdc_crtc->wq) {
+		kfree(tilcdc_crtc);
+		return NULL;
+	}
+	INIT_WORK(&tilcdc_crtc->recover_work, tilcdc_crtc_recover_work);
 
 	ret = drm_crtc_init(dev, crtc, &tilcdc_crtc_funcs);
 	if (ret < 0)
-- 
1.9.1

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