Re: [PATCH 3/3] drm/mediatek: mtk_disp_rdma: Enable/disable interrupt on bind/unbind

["CK Hu (胡俊光)" <ck.hu@mediatek.com>]

On Wed, 2025-09-24 at 12:37 +0200, AngeloGioacchino Del Regno wrote:
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> 
> 
> 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.")
> Link: https://lore.kernel.org/r/20250402083628.20111-6-angelogioacchino.delregno@collabora.com
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_disp_rdma.c | 34 ++++++++++++++----------
>  1 file changed, 20 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_rdma.c b/drivers/gpu/drm/mediatek/mtk_disp_rdma.c
> index c9d41d75e7f2..9fd9bb1ee544 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 = {
> @@ -313,16 +324,15 @@ static int mtk_disp_rdma_probe(struct platform_device *pdev)
>  {
>         struct device *dev = &pdev->dev;
>         struct mtk_disp_rdma *priv;
> -       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))
> @@ -345,21 +355,17 @@ 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);

Pending interrupt is cleared here, and interrupt is disabled here.
So the problem you mention would not happen.

Regards,
CK

> -
> -       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);
> 
> +       ret = devm_request_irq(dev, priv->irq, mtk_disp_rdma_irq_handler,
> +                              IRQF_NO_AUTOEN, 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);
> --
> 2.51.0
> 
>