[PATCH v4 6/9] drm/mediatek: dp: Enable event interrupt only when bridge attached

[AngeloGioacchino Del Regno]

In preparation for implementing support for aux-bus in this driver,
add a IRQ_NOAUTOEN flag to the event interrupt that we request at
probe time and manage the enablement of the ISR at bridge_attach
and detach time.

When aux-bus will be implemented, enabling the interrupt before
attaching the bridge will create an event storm and hang the kernel
during boot.
In any case, the interrupt handler anyway requires resources that
are initialized by mtk_dp_bridge_attach(), so it cannot do anything
meaningful without... and even crash, but that's not happening in
the current code because the HW remains unpowered until resources
are made available.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
Tested-by: Chen-Yu Tsai <wenst at chromium.org>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index 274119356dfb..eebcb32e67ee 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -100,6 +100,7 @@ struct mtk_dp_efuse_fmt {
 struct mtk_dp {
 	bool enabled;
 	bool need_debounce;
+	int irq;
 	u8 max_lanes;
 	u8 max_linkrate;
 	u8 rx_cap[DP_RECEIVER_CAP_SIZE];
@@ -2147,6 +2148,8 @@ 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);
 
 	return 0;
@@ -2163,6 +2166,7 @@ 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);
 	mtk_dp->drm_dev = NULL;
 	mtk_dp_poweroff(mtk_dp);
 	drm_dp_aux_unregister(&mtk_dp->aux);
@@ -2481,7 +2485,7 @@ static int mtk_dp_probe(struct platform_device *pdev)
 {
 	struct mtk_dp *mtk_dp;
 	struct device *dev = &pdev->dev;
-	int ret, irq_num;
+	int ret;
 
 	mtk_dp = devm_kzalloc(dev, sizeof(*mtk_dp), GFP_KERNEL);
 	if (!mtk_dp)
@@ -2490,9 +2494,9 @@ 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);
 
-	irq_num = platform_get_irq(pdev, 0);
-	if (irq_num < 0)
-		return dev_err_probe(dev, irq_num,
+	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");
 
 	mtk_dp->next_bridge = devm_drm_of_get_bridge(dev, dev->of_node, 1, 0);
@@ -2513,7 +2517,8 @@ static int mtk_dp_probe(struct platform_device *pdev)
 
 	spin_lock_init(&mtk_dp->irq_thread_lock);
 
-	ret = devm_request_threaded_irq(dev, irq_num, mtk_dp_hpd_event,
+	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);
-- 
2.40.1