+void vc4_hvs_mask_underrun(struct drm_device *dev, int channel)
+{
+ struct vc4_dev *vc4 = to_vc4_dev(dev);
+ u32 dispctrl = HVS_READ(SCALER_DISPCTRL);
+
+ dispctrl &= ~SCALER_DISPCTRL_DSPEISLUR(channel);
+
+ HVS_WRITE(SCALER_DISPCTRL, dispctrl);
+}
+
+void vc4_hvs_unmask_underrun(struct drm_device *dev, int channel)
+{
+ struct vc4_dev *vc4 = to_vc4_dev(dev);
+ u32 dispctrl = HVS_READ(SCALER_DISPCTRL);
+
+ dispctrl |= SCALER_DISPCTRL_DSPEISLUR(channel);
+
+ HVS_WRITE(SCALER_DISPSTAT,
+ SCALER_DISPSTAT_EUFLOW(channel));
+ HVS_WRITE(SCALER_DISPCTRL, dispctrl);
+}
+
+static void vc4_hvs_report_underrun(struct drm_device *dev)
+{
+ struct vc4_dev *vc4 = to_vc4_dev(dev);
+
+ atomic_inc(&vc4->underrun);
+ DRM_DEV_ERROR(dev->dev, "HVS underrun\n");
+}
+
+static irqreturn_t vc4_hvs_irq_handler(int irq, void *data)
+{
+ struct drm_device *dev = data;
+ struct vc4_dev *vc4 = to_vc4_dev(dev);
+ irqreturn_t irqret = IRQ_NONE;
+ int channel;
+ u32 control;
+ u32 status;
+
+ status = HVS_READ(SCALER_DISPSTAT);
+ control = HVS_READ(SCALER_DISPCTRL);
+
+ for (channel = 0; channel < SCALER_CHANNELS_COUNT; channel++) {
+ /* Interrupt masking is not always honored, so check it here. */
+ if (status & SCALER_DISPSTAT_EUFLOW(channel) &&
+ control & SCALER_DISPCTRL_DSPEISLUR(channel)) {
+ vc4_hvs_mask_underrun(dev, channel);
+ vc4_hvs_report_underrun(dev);
+
+ irqret = IRQ_HANDLED;
+ }
+ }
+
+ /* Clear every per-channel interrupt flag. */
+ HVS_WRITE(SCALER_DISPSTAT, SCALER_DISPSTAT_IRQMASK(0) |
+ SCALER_DISPSTAT_IRQMASK(1) |
+ SCALER_DISPSTAT_IRQMASK(2));
+
+ return irqret;
+}
+