linux-kernel - Re: [PATCH 2/3] drm/mediatek: mtk_disp_ovl: Enable/disable interrupt on bind/unbind

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Message-ID: <79e1cb6b8ddbd027096cc7f1d6a6f32ba4fbfbd9.camel@mediatek.com>
Date: Tue, 28 Oct 2025 09:55:32 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
CC: Alexandre Mergnat <amergnat@...libre.com>, "simona@...ll.ch"
	<simona@...ll.ch>, "dmitry.osipenko@...labora.com"
	<dmitry.osipenko@...labora.com>, "kernel@...labora.com"
	<kernel@...labora.com>, "linux-mediatek@...ts.infradead.org"
	<linux-mediatek@...ts.infradead.org>, "dri-devel@...ts.freedesktop.org"
	<dri-devel@...ts.freedesktop.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "djkurtz@...omium.org"
	<djkurtz@...omium.org>, "granquet@...libre.com" <granquet@...libre.com>,
	"p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
	Bibby Hsieh (謝濟遠) <Bibby.Hsieh@...iatek.com>,
	"airlied@...il.com" <airlied@...il.com>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "matthias.bgg@...il.com"
	<matthias.bgg@...il.com>, "littlecvr@...omium.org" <littlecvr@...omium.org>,
	Rex-BC Chen (陳柏辰) <Rex-BC.Chen@...iatek.com>
Subject: Re: [PATCH 2/3] drm/mediatek: mtk_disp_ovl: Enable/disable interrupt
 on bind/unbind

On Wed, 2025-09-24 at 12:37 +0200, AngeloGioacchino Del Regno wrote:
> External email : Please do not click links or open attachments until you have verified the sender or the content.
> 
> 
> 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.")
> 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 e0236353d499..8e20b45411fc 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);
> @@ -594,12 +595,18 @@ 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 = {
> @@ -611,16 +618,15 @@ static int mtk_disp_ovl_probe(struct platform_device *pdev)
>  {
>         struct device *dev = &pdev->dev;
>         struct mtk_disp_ovl *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))
> @@ -640,10 +646,10 @@ 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);

RDMA driver would clear pending interrupt and disable interrupt before request irq.
I would like the hardware would be in idle state when probe.
So OVL should do like RDMA.

Regards,
CK

>         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);
> 
> --
> 2.51.0
>