On Wed, 2026-02-25 at 09:38 +0000, Luca Leonardo Scorcia wrote:
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>
>
> 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
> [...]
> Modules linked in: mediatek_drm(+) drm_display_helper cec drm_client_lib
> drm_dma_helper drm_kms_helper panel_simple
> [...]
> Call trace:
> drm_mode_object_add+0x58/0x98 (P)
> __drm_encoder_init+0x48/0x140
> drm_encoder_init+0x6c/0xa0
> drm_simple_encoder_init+0x20/0x34 [drm_kms_helper]
> mtk_dsi_bind+0x34/0x13c [mediatek_drm]
> component_bind_all+0x120/0x280
> mtk_drm_bind+0x284/0x67c [mediatek_drm]
> try_to_bring_up_aggregate_device+0x23c/0x320
> __component_add+0xa4/0x198
> component_add+0x14/0x20
> mtk_dsi_host_attach+0x78/0x100 [mediatek_drm]
> mipi_dsi_attach+0x2c/0x50
> panel_simple_dsi_probe+0x4c/0x9c [panel_simple]
> mipi_dsi_drv_probe+0x1c/0x28
> really_probe+0xc0/0x3dc
> __driver_probe_device+0x80/0x160
> driver_probe_device+0x40/0x120
> __device_attach_driver+0xbc/0x17c
> bus_for_each_drv+0x88/0xf0
> __device_attach+0x9c/0x1cc
> device_initial_probe+0x54/0x60
> bus_probe_device+0x34/0xa0
> device_add+0x5b0/0x800
> mipi_dsi_device_register_full+0xdc/0x16c
> mipi_dsi_host_register+0xc4/0x17c
> mtk_dsi_probe+0x10c/0x260 [mediatek_drm]
> platform_probe+0x5c/0xa4
> really_probe+0xc0/0x3dc
> __driver_probe_device+0x80/0x160
> driver_probe_device+0x40/0x120
> __driver_attach+0xc8/0x1f8
> bus_for_each_dev+0x7c/0xe0
> driver_attach+0x24/0x30
> bus_add_driver+0x11c/0x240
> driver_register+0x68/0x130
> __platform_register_drivers+0x64/0x160
> mtk_drm_init+0x24/0x1000 [mediatek_drm]
> do_one_initcall+0x60/0x1d0
> do_init_module+0x54/0x240
> load_module+0x1838/0x1dc0
> init_module_from_file+0xd8/0xf0
> __arm64_sys_finit_module+0x1b4/0x428
> invoke_syscall.constprop.0+0x48/0xc8
> do_el0_svc+0x3c/0xb8
> el0_svc+0x34/0xe8
> el0t_64_sync_handler+0xa0/0xe4
> el0t_64_sync+0x198/0x19c
> Code: 52800022 941004ab 2a0003f3 37f80040 (29005a80)
> ---[ end trace 0000000000000000 ]---
Reviewed-by: CK Hu <ck.hu@mediatek.com>
>
> Fixes: e4732b590a77 ("drm/mediatek: dsi: Register DSI host after acquiring clocks and PHY")
> Signed-off-by: Luca Leonardo Scorcia <l.scorcia@gmail.com>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
> ---
> v3: Also initialize irq_wait_queue before calling platform_set_drvdata
> v2: Added Fixes tag
>
> drivers/gpu/drm/mediatek/mtk_dsi.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index d7726091819c..acee2227275b 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -1232,6 +1232,11 @@ static int mtk_dsi_probe(struct platform_device *pdev)
>
> dsi->host.ops = &mtk_dsi_ops;
> dsi->host.dev = dev;
> +
> + init_waitqueue_head(&dsi->irq_wait_queue);
> +
> + 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");
> @@ -1243,10 +1248,6 @@ static int mtk_dsi_probe(struct platform_device *pdev)
> return dev_err_probe(&pdev->dev, ret, "Failed to request DSI irq\n");
> }
>
> - 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;
>
> --
> 2.43.0
>
>