[v6,06/11] drm/mediatek: dp: Enable event interrupt only when bridge attached

Commit Message

AngeloGioacchino Del Regno July 17, 2023, 2:14 p.m. UTC

It is useless and error-prone to enable the DisplayPort event interrupt
before finishing to probe and install the driver, as the DP training
cannot happen before the entire pipeline is correctly set up, as the
interrupt handler also requires the full hardware to be initialized by
mtk_dp_bridge_attach().

Anyway, depending in which state the controller is left from the
bootloader, this may cause an interrupt storm and consequently hang
the kernel during boot, so, avoid enabling the interrupt until we
reach a clean state by adding the IRQ_NOAUTOEN flag before requesting
it at probe time and manage the enablement of the ISR in the .attach()
and .detach() handlers for the DP bridge.

Signed-off-by: AngeloGioacchino Del Regno <[e-mail]>
Tested-by: Chen-Yu Tsai <[e-mail]>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

Comments

Alexandre Mergnat July 20, 2023, 1:03 p.m. UTC | #1

On 17/07/2023 16:14, AngeloGioacchino Del Regno wrote:
> It is useless and error-prone to enable the DisplayPort event interrupt
> before finishing to probe and install the driver, as the DP training
> cannot happen before the entire pipeline is correctly set up, as the
> interrupt handler also requires the full hardware to be initialized by
> mtk_dp_bridge_attach().
> 
> Anyway, depending in which state the controller is left from the
> bootloader, this may cause an interrupt storm and consequently hang
> the kernel during boot, so, avoid enabling the interrupt until we
> reach a clean state by adding the IRQ_NOAUTOEN flag before requesting
> it at probe time and manage the enablement of the ISR in the .attach()
> and .detach() handlers for the DP bridge.

Reviewed-by: Alexandre Mergnat <[e-mail]>

Patch

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index e8d3bf310608..83e55f8dc84a 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];
@@ -2141,6 +2142,8 @@  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;
@@ -2157,6 +2160,7 @@  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);
@@ -2475,7 +2479,7 @@  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)
@@ -2484,9 +2488,9 @@  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);
@@ -2507,7 +2511,8 @@  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);