[PATCH v3 20/22] drm/tilcdc: Disable sync lost interrupt if it fires on every frame

[Jyri Sarha]

Disable the sync lost interrupt if it fires on every frame for 50
consecutive frames in a row. This is relatively sure sign of the sync
lost interrupt being stuck and firing on every frame even if the
display otherwise appears to work OK.

Signed-off-by: Jyri Sarha <jsarha at ti.com>
---
 drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c 
b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
index 5ee22c6..248e3ea 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -43,6 +43,9 @@ struct tilcdc_crtc {

        /* Only set if an external encoder is connected */
        bool simulate_vesa_sync;
+
+       int sync_lost_count;
+       bool frame_intact;
 };
 #define to_tilcdc_crtc(x) container_of(x, struct tilcdc_crtc, base)

@@ -662,6 +665,8 @@ out:
        pm_runtime_put_sync(dev->dev);
 }

+#define SYNC_LOST_COUNT_LIMIT 50
+
 irqreturn_t tilcdc_crtc_irq(struct drm_crtc *crtc)
 {
        struct tilcdc_crtc *tilcdc_crtc = to_tilcdc_crtc(crtc);
@@ -707,6 +712,11 @@ irqreturn_t tilcdc_crtc_irq(struct drm_crtc *crtc)

                        spin_unlock_irqrestore(&dev->event_lock, flags);
                }
+
+               if (tilcdc_crtc->frame_intact)
+                       tilcdc_crtc->sync_lost_count = 0;
+               else
+                       tilcdc_crtc->frame_intact = true;
        }

        if (priv->rev == 2) {
@@ -717,9 +727,18 @@ irqreturn_t tilcdc_crtc_irq(struct drm_crtc *crtc)
                tilcdc_write(dev, LCDC_END_OF_INT_IND_REG, 0);
        }

-       if (stat & LCDC_SYNC_LOST)
+       if (stat & LCDC_SYNC_LOST) {
                dev_err_ratelimited(dev->dev, "%s(0x%08x): Sync lost",
                                    __func__, stat);
+               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);
+                       tilcdc_write(dev, LCDC_INT_ENABLE_CLR_REG,
+                                    LCDC_SYNC_LOST);
+               }
+       }

        if (stat & LCDC_FIFO_UNDERFLOW)
                dev_err_ratelimited(dev->dev, "%s(0x%08x): FIFO underfow",
-- 
1.9.1