linux-kernel - [PATCH v2 4/5] drm/mediatek: mtk_disp_ovl: Enable/disable interrupt on bind/unbind

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Message-ID: <20250403104741.71045-5-angelogioacchino.delregno@collabora.com>
Date: Thu,  3 Apr 2025 12:47:40 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: chunkuang.hu@...nel.org
Cc: p.zabel@...gutronix.de,
	airlied@...il.com,
	simona@...ll.ch,
	matthias.bgg@...il.com,
	angelogioacchino.delregno@...labora.com,
	nancy.lin@...iatek.com,
	ck.hu@...iatek.com,
	djkurtz@...omium.org,
	littlecvr@...omium.org,
	bibby.hsieh@...iatek.com,
	dri-devel@...ts.freedesktop.org,
	linux-mediatek@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	wenst@...omium.org,
	kernel@...labora.com
Subject: [PATCH v2 4/5] drm/mediatek: mtk_disp_ovl: Enable/disable interrupt on bind/unbind

The OVL driver is installing an ISR in the probe function but, if
the component is not bound yet, the interrupt handler may call the
vblank_cb ahead of time (while probing other drivers) or too late
(while removing other drivers), possibly accessing memory that it
should not try to access by reusing stale pointers.

In order to fix this, add a new `irq` member to struct mtk_disp_ovl
and then add the IRQF_NO_AUTOEN flag to the irq while installing the
ISR to manually call enable_irq() and disable_irq() in the bind and
unbind callbacks respectively.

Note that since IRQF_TRIGGER_NONE is effectively 0 and doing nothing
this (fake) flag was dropped.

Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.")
Link: https://lore.kernel.org/r/20250402083628.20111-5-angelogioacchino.delregno@collabora.com
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
---
 drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
index df82cea4bb79..4d42cb3fee15 100644
--- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
+++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
@@ -161,6 +161,7 @@ struct mtk_disp_ovl {
 	struct drm_crtc			*crtc;
 	struct clk			*clk;
 	void __iomem			*regs;
+	int				irq;
 	struct cmdq_client_reg		cmdq_reg;
 	const struct mtk_disp_ovl_data	*data;
 	void				(*vblank_cb)(void *data);
@@ -587,12 +588,18 @@ void mtk_ovl_bgclr_in_off(struct device *dev)
 static int mtk_disp_ovl_bind(struct device *dev, struct device *master,
 			     void *data)
 {
+	struct mtk_disp_ovl *priv = dev_get_drvdata(dev);
+
+	enable_irq(priv->irq);
 	return 0;
 }
 
 static void mtk_disp_ovl_unbind(struct device *dev, struct device *master,
 				void *data)
 {
+	struct mtk_disp_ovl *priv = dev_get_drvdata(dev);
+
+	disable_irq(priv->irq);
 }
 
 static const struct component_ops mtk_disp_ovl_component_ops = {
@@ -605,16 +612,15 @@ static int mtk_disp_ovl_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct mtk_disp_ovl *priv;
 	struct resource *res;
-	int irq;
 	int ret;
 
 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
 
-	irq = platform_get_irq(pdev, 0);
-	if (irq < 0)
-		return irq;
+	priv->irq = platform_get_irq(pdev, 0);
+	if (priv->irq < 0)
+		return priv->irq;
 
 	priv->clk = devm_clk_get(dev, NULL);
 	if (IS_ERR(priv->clk))
@@ -635,10 +641,10 @@ static int mtk_disp_ovl_probe(struct platform_device *pdev)
 	priv->data = of_device_get_match_data(dev);
 	platform_set_drvdata(pdev, priv);
 
-	ret = devm_request_irq(dev, irq, mtk_disp_ovl_irq_handler,
-			       IRQF_TRIGGER_NONE, dev_name(dev), priv);
+	ret = devm_request_irq(dev, priv->irq, mtk_disp_ovl_irq_handler,
+			       IRQF_NO_AUTOEN, dev_name(dev), priv);
 	if (ret < 0)
-		return dev_err_probe(dev, ret, "Failed to request irq %d\n", irq);
+		return dev_err_probe(dev, ret, "Failed to request irq %d\n", priv->irq);
 
 	pm_runtime_enable(dev);
 
-- 
2.48.1