drm/mediatek: dp: Don't register HPD interrupt handler for eDP case

The interrupt handler for HPD is useful only if a display is actually
supposed to be hotpluggable, as that manages the machinery to perform
cable (un)plug detection, debouncing and setup for re-training.

Since eDP panels are not supposed to be hotpluggable we can avoid
using the HPD interrupts altogether and rely on HPD polling only
for the suspend/resume case, saving us some spinlocking action and
the overhead of interrupts firing at every suspend/resume cycle,
achieving a faster (even if just slightly) display resume.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20230725073234.55892-12-angelogioacchino.delregno@collabora.com/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

Author: AngeloGioacchino Del Regno

drivers/gpu/drm/mediatek/mtk_dp.c

@@ -2182,9 +2182,11 @@ static int mtk_dp_bridge_attach(struct drm_bridge *bridge,
 
 	mtk_dp->drm_dev = bridge->dev;
 
-	irq_clear_status_flags(mtk_dp->irq, IRQ_NOAUTOEN);
-	enable_irq(mtk_dp->irq);
-	mtk_dp_hwirq_enable(mtk_dp, true);
+	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP) {
+		irq_clear_status_flags(mtk_dp->irq, IRQ_NOAUTOEN);
+		enable_irq(mtk_dp->irq);
+		mtk_dp_hwirq_enable(mtk_dp, true);
+	}
 
 	return 0;
 
@@ -2199,8 +2201,10 @@ static void mtk_dp_bridge_detach(struct drm_bridge *bridge)
 {
 	struct mtk_dp *mtk_dp = mtk_dp_from_bridge(bridge);
 
-	mtk_dp_hwirq_enable(mtk_dp, false);
-	disable_irq(mtk_dp->irq);
+	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP) {
+		mtk_dp_hwirq_enable(mtk_dp, false);
+		disable_irq(mtk_dp->irq);
+	}
 	mtk_dp->drm_dev = NULL;
 	mtk_dp_poweroff(mtk_dp);
 	drm_dp_aux_unregister(&mtk_dp->aux);
@@ -2579,32 +2583,44 @@ static int mtk_dp_probe(struct platform_device *pdev)
 	mtk_dp->dev = dev;
 	mtk_dp->data = (struct mtk_dp_data *)of_device_get_match_data(dev);
 
-	mtk_dp->irq = platform_get_irq(pdev, 0);
-	if (mtk_dp->irq < 0)
-		return dev_err_probe(dev, mtk_dp->irq,
-				     "failed to request dp irq resource\n");
-
 	ret = mtk_dp_dt_parse(mtk_dp, pdev);
 	if (ret)
 		return dev_err_probe(dev, ret, "Failed to parse dt\n");
 
+	/*
+	 * Request the interrupt and install service routine only if we are
+	 * on full DisplayPort.
+	 * For eDP, polling the HPD instead is more convenient because we
+	 * don't expect any (un)plug events during runtime, hence we can
+	 * avoid some locking.
+	 */
+	if (mtk_dp->data->bridge_type != DRM_MODE_CONNECTOR_eDP) {
+		mtk_dp->irq = platform_get_irq(pdev, 0);
+		if (mtk_dp->irq < 0)
+			return dev_err_probe(dev, mtk_dp->irq,
+					     "failed to request dp irq resource\n");
+
+		spin_lock_init(&mtk_dp->irq_thread_lock);
+
+		irq_set_status_flags(mtk_dp->irq, IRQ_NOAUTOEN);
+		ret = devm_request_threaded_irq(dev, mtk_dp->irq, mtk_dp_hpd_event,
+						mtk_dp_hpd_event_thread,
+						IRQ_TYPE_LEVEL_HIGH, dev_name(dev),
+						mtk_dp);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					     "failed to request mediatek dptx irq\n");
+
+		mtk_dp->need_debounce = true;
+		timer_setup(&mtk_dp->debounce_timer, mtk_dp_debounce_timer, 0);
+	}
+
 	mtk_dp->aux.name = "aux_mtk_dp";
 	mtk_dp->aux.dev = dev;
 	mtk_dp->aux.transfer = mtk_dp_aux_transfer;
 	mtk_dp->aux.wait_hpd_asserted = mtk_dp_wait_hpd_asserted;
 	drm_dp_aux_init(&mtk_dp->aux);
 
-	spin_lock_init(&mtk_dp->irq_thread_lock);
-
-	irq_set_status_flags(mtk_dp->irq, IRQ_NOAUTOEN);
-	ret = devm_request_threaded_irq(dev, mtk_dp->irq, mtk_dp_hpd_event,
-					mtk_dp_hpd_event_thread,
-					IRQ_TYPE_LEVEL_HIGH, dev_name(dev),
-					mtk_dp);
-	if (ret)
-		return dev_err_probe(dev, ret,
-				     "failed to request mediatek dptx irq\n");
-
 	platform_set_drvdata(pdev, mtk_dp);
 
 	if (mtk_dp->data->audio_supported) {
@@ -2626,9 +2642,6 @@ static int mtk_dp_probe(struct platform_device *pdev)
 	mtk_dp->bridge.of_node = dev->of_node;
 	mtk_dp->bridge.type = mtk_dp->data->bridge_type;
 
-	mtk_dp->need_debounce = true;
-	timer_setup(&mtk_dp->debounce_timer, mtk_dp_debounce_timer, 0);
-
 	if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP) {
 		/*
 		 * Set the data lanes to idle in case the bootloader didn't
@@ -2639,6 +2652,9 @@ static int mtk_dp_probe(struct platform_device *pdev)
 		mtk_dp_initialize_aux_settings(mtk_dp);
 		mtk_dp_power_enable(mtk_dp);
 
+		/* Disable HW interrupts: we don't need any for eDP */
+		mtk_dp_hwirq_enable(mtk_dp, false);
+
 		/*
 		 * Power on the AUX to allow reading the EDID from aux-bus:
 		 * please note that it is necessary to call power off in the
@@ -2684,7 +2700,8 @@ static int mtk_dp_remove(struct platform_device *pdev)
 
 	pm_runtime_put(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
-	del_timer_sync(&mtk_dp->debounce_timer);
+	if (mtk_dp->data->bridge_type != DRM_MODE_CONNECTOR_eDP)
+		del_timer_sync(&mtk_dp->debounce_timer);
 	platform_device_unregister(mtk_dp->phy_dev);
 	if (mtk_dp->audio_pdev)
 		platform_device_unregister(mtk_dp->audio_pdev);
@@ -2698,7 +2715,8 @@ static int mtk_dp_suspend(struct device *dev)
 	struct mtk_dp *mtk_dp = dev_get_drvdata(dev);
 
 	mtk_dp_power_disable(mtk_dp);
-	mtk_dp_hwirq_enable(mtk_dp, false);
+	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP)
+		mtk_dp_hwirq_enable(mtk_dp, false);
 	pm_runtime_put_sync(dev);
 
 	return 0;
@@ -2710,7 +2728,8 @@ static int mtk_dp_resume(struct device *dev)
 
 	pm_runtime_get_sync(dev);
 	mtk_dp_init_port(mtk_dp);
-	mtk_dp_hwirq_enable(mtk_dp, true);
+	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP)
+		mtk_dp_hwirq_enable(mtk_dp, true);
 	mtk_dp_power_enable(mtk_dp);
 
 	return 0;