linux-kernel - Re: [PATCH] drm/mediatek: dsi: Store driver data before invoking mipi_dsi_host

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Message-ID: <CAORyz2J=zEMgNS6n6ouVZ3QA1moYfP053Jr5vhcscR9nDmKOfA@mail.gmail.com>
Date: Mon, 9 Feb 2026 19:46:42 +0100
From: Luca Leonardo Scorcia <l.scorcia@...il.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: linux-mediatek@...ts.infradead.org, 
	Chun-Kuang Hu <chunkuang.hu@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Matthias Brugger <matthias.bgg@...il.com>, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] drm/mediatek: dsi: Store driver data before invoking mipi_dsi_host_register

Il giorno lun 9 feb 2026 alle ore 12:40 AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com> ha scritto:
>
> Il 09/02/26 10:05, Luca Leonardo Scorcia ha scritto:
> > The call to mipi_dsi_host_register triggers a callback to mtk_dsi_bind,
> > which uses dev_get_drvdata to retrieve the mtk_dsi struct, so this
> > structure needs to be stored inside the driver data before invoking it.
> >
> > As drvdata is currently uninitialized it leads to a crash when
> > registering the DSI DRM encoder right after acquiring
> > the mode_config.idr_mutex, blocking all subsequent DRM operations.
> >
> > Fixes the following crash during mediatek-drm probe (tested on Xiaomi
> > Smart Clock x04g):
> >
> > Unable to handle kernel NULL pointer dereference at virtual address
> >   0000000000000040
> > [...]
> > ---[ end trace 0000000000000000 ]---
> >
> > Signed-off-by: Luca Leonardo Scorcia <l.scorcia@...il.com>
>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
>
> ... but wait, what have I just read? Xiaomi Smart Clock?! MT8167?
>
> Are you running upstream on this device?
> If so, why don't you also contribute a nice devicetree to get this device finally
> upstream?!?! :-)

That's correct! Most of the work had already been done by the
wonderful people at postmarketOS, I just had to connect the dots. Some
crucial patches (mt6392 regulator, mt8167 display nodes) were
submitted in the past but weren't merged for various reasons.

Just rebased on v6.19: https://pasteboard.co/6bXQeWlwUqmz.jpg

I am trying to get it working as much as I can, then cleanup and
submit. At the moment storage, usb networking, rtc, buttons, screen,
touch, backlight, light/presence sensors, drm and gce are all working;
still missing wifi/bt, audio and cpuidle.

> Cheers,
> Angelo
>
> > ---
> >   drivers/gpu/drm/mediatek/mtk_dsi.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > index 4c2983852596..2358407b8a6b 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > @@ -1232,6 +1232,8 @@ static int mtk_dsi_probe(struct platform_device *pdev)
> >
> >       dsi->host.ops = &mtk_dsi_ops;
> >       dsi->host.dev = dev;
> > +     platform_set_drvdata(pdev, dsi);
> > +
> >       ret = mipi_dsi_host_register(&dsi->host);
> >       if (ret < 0)
> >               return dev_err_probe(dev, ret, "Failed to register DSI host\n");
> > @@ -1254,8 +1256,6 @@ static int mtk_dsi_probe(struct platform_device *pdev)
> >
> >       init_waitqueue_head(&dsi->irq_wait_queue);
> >
> > -     platform_set_drvdata(pdev, dsi);
> > -
> >       dsi->bridge.of_node = dev->of_node;
> >       dsi->bridge.type = DRM_MODE_CONNECTOR_DSI;
> >
>
>


-- 
Luca Leonardo Scorcia
l.scorcia@...il.com