[RESEND PATCH] drm/mediatek: Add error handling for old state CRTC in atomic_disable

[AngeloGioacchino Del Regno]

Il 28/07/25 04:48, Jason-JH Lin ha scritto:
> Introduce error handling to address an issue where, after a hotplug
> event, the cursor continues to update. This situation can lead to a
> kernel panic due to accessing the NULL `old_state->crtc`.
> 
> E,g.
> Unable to handle kernel NULL pointer dereference at virtual address
> Call trace:
>   mtk_crtc_plane_disable+0x24/0x140
>   mtk_plane_atomic_update+0x8c/0xa8
>   drm_atomic_helper_commit_planes+0x114/0x2c8
>   drm_atomic_helper_commit_tail_rpm+0x4c/0x158
>   commit_tail+0xa0/0x168
>   drm_atomic_helper_commit+0x110/0x120
>   drm_atomic_commit+0x8c/0xe0
>   drm_atomic_helper_update_plane+0xd4/0x128
>   __setplane_atomic+0xcc/0x110
>   drm_mode_cursor_common+0x250/0x440
>   drm_mode_cursor_ioctl+0x44/0x70
>   drm_ioctl+0x264/0x5d8
>   __arm64_sys_ioctl+0xd8/0x510
>   invoke_syscall+0x6c/0xe0
>   do_el0_svc+0x68/0xe8
>   el0_svc+0x34/0x60
>   el0t_64_sync_handler+0x1c/0xf8
>   el0t_64_sync+0x180/0x188
> 
> Adding NULL pointer checks to ensure stability by preventing operations
> on an invalid CRTC state.
> 
> Fixes: d208261e9f7c ("drm/mediatek: Add wait_event_timeout when disabling plane")
> Signed-off-by: Jason-JH Lin <jason-jh.lin at mediatek.com>

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>