Here is the error message which is filling up my dmesg:

[   24.621271] WARNING: CPU: 1 PID: 252 at drivers/gpu/drm/vc4/vc4_hdmi_regs.h:445 vc5_hdmi_set_timings+0x984/0xd80 [vc4]
[   24.621304] Modules linked in: snd_soc_hdmi_codec vc4 joydev drm_kms_helper cec snd_usb_audio btsdio snd_soc_core snd_hwdep snd_usbmidi_lib bluetooth snd_compress ac97_bus snd_pcm_dmaengine hid_multitouch snd_seq_midi snd_seq_midi_event ecdh_generic ecc snd_rawmidi brcmfmac brcmutil cfg80211 snd_seq snd_bcm2835(C) snd_pcm raspberrypi_hwmon bcm2835_isp(C) bcm2835_codec(C) bcm2835_v4l2(C) bcm2835_mmal_vchiq(C) videobuf2_vmalloc v4l2_mem2mem videobuf2_dma_contig videobuf2_memops snd_seq_device vc_sm_cma(C) videobuf2_v4l2 videobuf2_common snd_timer videodev mc bcm2835_gpiomem rpivid_mem snd fb_sys_fops syscopyarea sysfillrect nvmem_rmem sysimgblt uio_pdrv_genirq uio sch_fq_codel ppdev lp parport sunrpc ip_tables x_tables autofs4 btrfs blake2b_generic xor xor_neon zstd_compress raid6_pq libcrc32c hid_generic usbhid uas usb_storage v3d gpu_sched drm i2c_brcmstb crct10dif_ce xhci_pci xhci_pci_renesas phy_generic aes_arm64
[   24.621468] CPU: 1 PID: 252 Comm: plymouthd Tainted: G        WC        5.13.0-1007-raspi #8-Ubuntu
[   24.621473] Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
[   24.621476] pstate: 40400005 (nZcv daif +PAN -UAO -TCO BTYPE=--)
[   24.621481] pc : vc5_hdmi_set_timings+0x984/0xd80 [vc4]
[   24.621507] lr : vc4_hdmi_encoder_pre_crtc_configure+0x3b0/0x514 [vc4]
[   24.621532] sp : ffff80001094b920
[   24.621535] x29: ffff80001094b920 x28: 0000000000000000 x27: 0000000000000000
[   24.621543] x26: 0000000000000000 x25: 0000000000000004 x24: 0000000000000004
[   24.621551] x23: 0000000000000001 x22: ffff4d8bcafcf000 x21: 0000000004080780
[   24.621559] x20: ffff4d8bc43b5818 x19: ffff4d8bc8d04080 x18: 0000000000000000
[   24.621568] x17: 0000000000000000 x16: ffffdb1af5730f80 x15: ffff4d8bc70982e0
[   24.621576] x14: 0000000000000000 x13: 0000000000000010 x12: ffff800010035000
[   24.621584] x11: 0000000000000001 x10: 0000000000000001 x9 : ffffdb1a7bedddf0
[   24.621592] x8 : 0000000000000000 x7 : ffff800010035038 x6 : 0000000000000000
[   24.621600] x5 : 0000000000000002 x4 : 0000000000000002 x3 : 0000000000000002
[   24.621608] x2 : ffffdb1a7bef1018 x1 : 0000000000000080 x0 : 0000000000280020
[   24.621616] Call trace:
[   24.621619]  vc5_hdmi_set_timings+0x984/0xd80 [vc4]
[   24.621644]  vc4_hdmi_encoder_pre_crtc_configure+0x3b0/0x514 [vc4]
[   24.621669]  vc4_crtc_atomic_enable+0x9c/0x140 [vc4]
[   24.621694]  drm_atomic_helper_commit_modeset_enables+0x20c/0x254 [drm_kms_helper]
[   24.621749]  vc4_atomic_commit_tail+0x224/0x36c [vc4]
[   24.621775]  commit_tail+0xac/0x190 [drm_kms_helper]
[   24.621819]  drm_atomic_helper_commit+0x168/0x380 [drm_kms_helper]
[   24.621862]  drm_atomic_commit+0x58/0x70 [drm]
[   24.621951]  drm_atomic_helper_set_config+0xe0/0x120 [drm_kms_helper]
[   24.621997]  drm_mode_setcrtc+0x1b4/0x6e0 [drm]
[   24.622082]  drm_ioctl_kernel+0xd0/0x120 [drm]
[   24.622162]  drm_ioctl+0x25c/0x4f0 [drm]
[   24.622242]  __arm64_sys_ioctl+0xb4/0xfc
[   24.622252]  invoke_syscall+0x50/0x120
[   24.622259]  el0_svc_common.constprop.0+0x6c/0x1a0
[   24.622263]  do_el0_svc+0x34/0xa0
[   24.622267]  el0_svc+0x2c/0x54
[   24.622274]  el0_sync_handler+0xa4/0x130
[   24.622279]  el0_sync+0x19c/0x1c0
[   24.622283] ---[ end trace adc8739fe8726a86 ]---
[   24.622361] ------------[ cut here ]------------