linux-kernel - Re: [PATCH v1 4/5] drm/mediatek: mtk_disp_ovl: Enable/disable interrupt on bind/unbind

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Message-ID: <CAGXv+5E1qShE1LqgFL6rrgRzjwFUPoBqYdhO-sgNzmMqQsMS0Q@mail.gmail.com>
Date: Wed, 2 Apr 2025 17:38:03 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: chunkuang.hu@...nel.org, p.zabel@...gutronix.de, airlied@...il.com, 
	simona@...ll.ch, matthias.bgg@...il.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, kernel@...labora.com
Subject: Re: [PATCH v1 4/5] drm/mediatek: mtk_disp_ovl: Enable/disable
 interrupt on bind/unbind

On Wed, Apr 2, 2025 at 4:36 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com> wrote:
>
> 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 set the NOAUTOEN flag to the irq before installing the ISR
> to manually call 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_ovl.c | 19 +++++++++++++------
>  1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> index df82cea4bb79..1bff3a1273f6 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 +641,11 @@ 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,
> +       irq_set_status_flags(priv->irq, IRQ_NOAUTOEN);
> +       ret = devm_request_irq(dev, priv->irq, mtk_disp_ovl_irq_handler,
>                                IRQF_TRIGGER_NONE, dev_name(dev), priv);

Use IRQF_NO_AUTOEN here? Also, IRQF_TRIGGER_NONE can be dropped.

Make sense otherwise.

ChenYu

>         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
>