[PATCH v5 1/4] drm/tilcdc: Recover from sync lost error flood by resetting the LCDC

[Jyri Sarha]

Recover from sync lost error flood by resetting the LCDC instead 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 | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c 
b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
index 0d09acc..c787349 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -55,6 +55,7 @@ struct tilcdc_crtc {

        int sync_lost_count;
        bool frame_intact;
+       struct work_struct recover_work;
 };
 #define to_tilcdc_crtc(x) container_of(x, struct tilcdc_crtc, base)

@@ -252,6 +253,25 @@ static bool tilcdc_crtc_is_on(struct drm_crtc *crtc)
        return crtc->state && crtc->state->enable && crtc->state->active;
 }

+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__);
+
+       drm_modeset_lock_crtc(crtc, NULL);
+
+       if (!tilcdc_crtc_is_on(crtc))
+               goto out;
+
+       tilcdc_crtc_disable(crtc);
+       tilcdc_crtc_enable(crtc);
+out:
+       drm_modeset_unlock_crtc(crtc);
+}
+
 static void tilcdc_crtc_destroy(struct drm_crtc *crtc)
 {
        struct tilcdc_crtc *tilcdc_crtc = to_tilcdc_crtc(crtc);
@@ -838,9 +858,12 @@ 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", __func__, stat);
+                               dev_err(dev->dev, "%s(0x%08x): Sync lost flood 
detected, recovering", __func__, stat);
+                               queue_work(system_wq,
+                                          &tilcdc_crtc->recover_work);
                                tilcdc_write(dev, LCDC_INT_ENABLE_CLR_REG,
                                             LCDC_SYNC_LOST);
+                               tilcdc_crtc->sync_lost_count = 0;
                        }
                }

@@ -880,6 +903,7 @@ struct drm_crtc *tilcdc_crtc_create(struct drm_device *dev)
                        "unref", unref_worker);

        spin_lock_init(&tilcdc_crtc->irq_lock);
+       INIT_WORK(&tilcdc_crtc->recover_work, tilcdc_crtc_recover_work);

        ret = drm_crtc_init_with_planes(dev, crtc,
                                        &tilcdc_crtc->primary,
-- 
1.9.1