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

[Jyri Sarha]

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 at ti.com>
---
 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