linux-kernel - Re: [PATCH] drm/mipi-dsi: Only remove child devices that match the dsi device type

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Message-ID: <2718437.9Mp67QZiUf@diego>
Date: Wed, 07 Jan 2026 13:18:00 +0100
From: Heiko Stübner <heiko@...ech.de>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Sandy Huang <hjc@...k-chips.com>, Andy Yan <andy.yan@...k-chips.com>,
 Chaoyi Chen <kernel@...kyi.com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-rockchip@...ts.infradead.org, Chaoyi Chen <chaoyi.chen@...k-chips.com>
Subject:
 Re: [PATCH] drm/mipi-dsi: Only remove child devices that match the dsi device
 type

Am Mittwoch, 3. Dezember 2025, 12:50:28 Mitteleuropäische Normalzeit schrieb Chaoyi Chen:
> From: Chaoyi Chen <chaoyi.chen@...k-chips.com>
> 
> This patch checks whether the device is a valid mipi_dsi_device before
> accessing it in mipi_dsi_remove_device_fn().
> 
> The mipi_dsi_host_unregister() assumes that all child devices of the
> host device are mipi_dsi_devices and uses mipi_dsi_remove_device_fn()
> to perform subsequent operations specific to mipi_dsi_device.
> 
> In rockchip platform, for dw-mipi-dsi-rockchip.c, it creates a dphy
> device, and it use the dsi host device as its parent device.
> 
> And when we call dw_mipi_dsi_remove() in
> dw_mipi_dsi_rockchip_remove(), mipi_dsi_host_unregister() will get
> such a dphy child device and treat it as an mipi_dsi_device, which
> will lead to a further panic.
> 
> Signed-off-by: Chaoyi Chen <chaoyi.chen@...k-chips.com>
> ---
>  drivers/gpu/drm/drm_mipi_dsi.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
> index a712e177b350..5b9cc799eb87 100644
> --- a/drivers/gpu/drm/drm_mipi_dsi.c
> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
> @@ -349,7 +349,12 @@ EXPORT_SYMBOL(mipi_dsi_host_register);
>  
>  static int mipi_dsi_remove_device_fn(struct device *dev, void *priv)
>  {
> -	struct mipi_dsi_device *dsi = to_mipi_dsi_device(dev);
> +	struct mipi_dsi_device *dsi;
> +
> +	if (!dev_is_mipi_dsi(dev))
> +		return 0;
> +
> +	dsi = to_mipi_dsi_device(dev);
>  
>  	if (dsi->attached)
>  		mipi_dsi_detach(dsi);
> 

This makes a lot of sense.

Reviewed-by: Heiko Stuebner <heiko@...ech.de>


For people reading along:
The DSI controllers on the RK3399 uses a phy that is _inside_ the
DW-DSI controller, instead of a separate IP block.

But this internal PHY can also work as a receiver for camera data
for the ISP block in the RK3399.

Heiko