linux-kernel - [PATCH v1 5/5] drm/mediatek: mtk_disp_rdma: Enable/disable interrupt on bind/unbind

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Message-ID: <20250402083628.20111-6-angelogioacchino.delregno@collabora.com>
Date: Wed,  2 Apr 2025 10:36:28 +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 v1 5/5] drm/mediatek: mtk_disp_rdma: Enable/disable interrupt on bind/unbind

The RDMA 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, like done in the OVL driver, add a new `irq`
member to struct mtk_disp_ovl and then set the NOAUTOEN flag to
the irq before installing the ISR to manually disable and clear
the hwirqs with register writes, and enable_irq() and disable_irq()
in the bind and unbind callbacks respectively.

Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
---
 drivers/gpu/drm/mediatek/mtk_disp_rdma.c | 35 ++++++++++++++----------
 1 file changed, 21 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
index bf47790e4d6b..8c5021365a04 100644
--- a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
+++ b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
@@ -81,6 +81,7 @@ struct mtk_disp_rdma_data {
 struct mtk_disp_rdma {
 	struct clk			*clk;
 	void __iomem			*regs;
+	int				irq;
 	struct cmdq_client_reg		cmdq_reg;
 	const struct mtk_disp_rdma_data	*data;
 	void				(*vblank_cb)(void *data);
@@ -295,13 +296,23 @@ void mtk_rdma_layer_config(struct device *dev, unsigned int idx,
 static int mtk_disp_rdma_bind(struct device *dev, struct device *master,
 			      void *data)
 {
-	return 0;
+	struct mtk_disp_rdma *priv = dev_get_drvdata(dev);
+
+	/* Disable and clear pending interrupts */
+	writel(0x0, priv->regs + DISP_REG_RDMA_INT_ENABLE);
+	writel(0x0, priv->regs + DISP_REG_RDMA_INT_STATUS);
 
+	enable_irq(priv->irq);
+
+	return 0;
 }
 
 static void mtk_disp_rdma_unbind(struct device *dev, struct device *master,
 				 void *data)
 {
+	struct mtk_disp_rdma *priv = dev_get_drvdata(dev);
+
+	disable_irq(priv->irq);
 }
 
 static const struct component_ops mtk_disp_rdma_component_ops = {
@@ -314,16 +325,15 @@ static int mtk_disp_rdma_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct mtk_disp_rdma *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))
@@ -347,21 +357,18 @@ static int mtk_disp_rdma_probe(struct platform_device *pdev)
 	if (ret && (ret != -EINVAL))
 		return dev_err_probe(dev, ret, "Failed to get rdma fifo size\n");
 
-	/* Disable and clear pending interrupts */
-	writel(0x0, priv->regs + DISP_REG_RDMA_INT_ENABLE);
-	writel(0x0, priv->regs + DISP_REG_RDMA_INT_STATUS);
-
-	ret = devm_request_irq(dev, irq, mtk_disp_rdma_irq_handler,
-			       IRQF_TRIGGER_NONE, dev_name(dev), priv);
-	if (ret < 0)
-		return dev_err_probe(dev, ret, "Failed to request irq %d\n", irq);
-
 	priv->data = of_device_get_match_data(dev);
 
 	platform_set_drvdata(pdev, priv);
 
 	pm_runtime_enable(dev);
 
+	irq_set_status_flags(priv->irq, IRQ_NOAUTOEN);
+	ret = devm_request_irq(dev, priv->irq, mtk_disp_rdma_irq_handler,
+			       IRQF_TRIGGER_NONE, dev_name(dev), priv);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to request irq %d\n", priv->irq);
+
 	ret = component_add(dev, &mtk_disp_rdma_component_ops);
 	if (ret) {
 		pm_runtime_disable(dev);
-- 
2.48.1