[   78.451779] 8<--- cut here ---
[   78.454889] Unhandled fault: asynchronous external abort (0x1211) at 0x00000000
[   78.462313] pgd = 908cc3e1
[   78.465058] [00000000] *pgd=06cd6003, *pmd=00000000
[   78.470014] Internal error: : 1211 [#1] PREEMPT SMP ARM
[   78.475315] Modules linked in: dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua btsdio bluetooth ecdh_generic ecc bcm2835_codec(CE) bcm2835_isp(CE) brcmfmac bcm2835_v4l2(CE) bcm2835_mmal_vchiq(CE) v4l2_mem2mem videobuf2_dma_contig videobuf2_vmalloc videobuf2_memops brcmutil videobuf2_v4l2 videobuf2_common cfg80211 snd_bcm2835(CE) videodev snd_pcm snd_timer raspberrypi_hwmon mc snd vc_sm_cma(CE) bcm2835_gpiomem rpivid_mem uio_pdrv_genirq uio sch_fq_codel drm ip_tables x_tables autofs4 btrfs blake2b_generic raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor xor_neon raid6_pq libcrc32c raid1 raid0 multipath linear crc32_arm_ce spidev xhci_pci xhci_pci_renesas phy_generic aes_arm_bs crypto_simd cryptd
[   78.540823] CPU: 1 PID: 1975 Comm: cat Tainted: G         C  E     5.11.0-1001-raspi #1
[   78.548945] Hardware name: BCM2711
[   78.552392] PC is at regmap_mmio_read32le+0x24/0x28
[   78.557344] LR is at regmap_mmio_read+0x48/0x64
[   78.561939] pc : [<c08e6664>]    lr : [<c08e6838>]    psr: 200f0093
[   78.568296] sp : c80f7d88  ip : c80f7d98  fp : c80f7d94
[   78.573594] r10: 00000014  r9 : c8180000  r8 : c80f7f68
[   78.578892] r7 : c80f7e44  r6 : c80f7e44  r5 : 00000014  r4 : c5065680
[   78.585515] r3 : f1061014  r2 : c80f7e44  r1 : 00000014  r0 : 00000000
[   78.592139] Flags: nzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment user
[   78.599469] Control: 30c5383d  Table: 06e3aa00  DAC: 55555555
[   78.605298] Process cat (pid: 1975, stack limit = 0xe4dc88d8)
[   78.611127] Stack: (0xc80f7d88 to 0xc80f8000)
[   78.615546] 7d80:                   c80f7db4 c80f7d98 c08e6838 c08e664c c5013e00 00000014
[   78.623845] 7da0: c5013e00 c80f7e44 c80f7dc4 c80f7db8 c08db9f0 c08e67fc c80f7df4 c80f7dc8
[   78.632144] 7dc0: c08df3d0 c08db9d8 00000008 c5013e00 00000014 c80f7e44 00000014 c80f7f68
[   78.640444] 7de0: c8180000 00000014 c80f7e14 c80f7df8 c08df538 c08df36c 0000004b c5013e00
[   78.648744] 7e00: 00000014 00000014 c80f7e84 c80f7e18 c08e5188 c08df4f8 00000014 c1189598
[   78.657044] 7e20: 00000004 b6a5e000 c111a22c c111a224 00000000 000001fc 00020000 c140a088
[   78.665344] 7e40: ffeee000 00000000 00000046 00000000 ffffe000 c140a088 c80f7f68 b6a5e000
[   78.673644] 7e60: c7ac6000 b6a5e000 00020000 c49917f8 c80f7f68 c061f614 c80f7ea4 c80f7e88
[   78.681944] 7e80: c08e54a8 c08e4ff0 00020000 c80f7f68 b6a5e000 c08e546c c80f7ecc c80f7ea8
[   78.690243] 7ea0: c061f678 c08e5478 00020000 00000000 c7ac6000 ffffe000 b6a5e000 c80f7f68
[   78.698543] 7ec0: c80f7f64 c80f7ed0 c0489f10 c061f620 b6a5d000 c742ada8 c6e3aa10 00000000
[   78.706843] 7ee0: 00000000 00000001 00000000 00000000 ffeee2e8 e933e1b8 00000000 c0d7e030
[   78.715143] 7f00: c80f7f2c c140a088 c80f7fb0 c140a088 c80f7fb0 00000a07 b6a5d000 eeecce00
[   78.723442] 7f20: c80f7f74 c80f7f30 c0d7e030 c0290594 00000000 c140a088 c80f7f90 c7ac6000
[   78.731741] 7f40: c7ac6000 00000000 00000000 c0200204 c80f6000 00000003 c80f7f94 c80f7f68
[   78.740041] 7f60: c048a574 c0489e54 00000000 00000000 c0216bdc c140a088 b6a5e007 00020000
[   78.748340] 7f80: b6f51f50 00000003 c80f7fa4 c80f7f98 c048a610 c048a50c 00000000 c80f7fa8
[   78.756639] 7fa0: c0200040 c048a604 b6a5e007 00020000 00000003 b6a5e000 00020000 00000000
[   78.764939] 7fc0: b6a5e007 00020000 b6f51f50 00000003 00000003 00000000 00020000 be8aa614
[   78.773239] 7fe0: 00000003 be8aa360 b6ebc1e7 b6e42216 600f0030 00000003 00000000 00000000
[   78.781537] Backtrace: 
[   78.784017] [<c08e6640>] (regmap_mmio_read32le) from [<c08e6838>] (regmap_mmio_read+0x48/0x64)
[   78.792761] [<c08e67f0>] (regmap_mmio_read) from [<c08db9f0>] (_regmap_bus_reg_read+0x24/0x28)
[   78.801508]  r7:c80f7e44 r6:c5013e00 r5:00000014 r4:c5013e00
[   78.807248] [<c08db9cc>] (_regmap_bus_reg_read) from [<c08df3d0>] (_regmap_read+0x70/0x18c)
[   78.815728] [<c08df360>] (_regmap_read) from [<c08df538>] (regmap_read+0x4c/0x70)
[   78.823329]  r10:00000014 r9:c8180000 r8:c80f7f68 r7:00000014 r6:c80f7e44 r5:00000014
[   78.831275]  r4:c5013e00 r3:00000008
[   78.834899] [<c08df4ec>] (regmap_read) from [<c08e5188>] (regmap_read_debugfs+0x1a4/0x448)
[   78.843294]  r7:00000014 r6:00000014 r5:c5013e00 r4:0000004b
[   78.849034] [<c08e4fe4>] (regmap_read_debugfs) from [<c08e54a8>] (regmap_map_read_file+0x3c/0x44)
[   78.858048]  r10:c061f614 r9:c80f7f68 r8:c49917f8 r7:00020000 r6:b6a5e000 r5:c7ac6000
[   78.865994]  r4:b6a5e000
[   78.868558] [<c08e546c>] (regmap_map_read_file) from [<c061f678>] (full_proxy_read+0x64/0x94)
[   78.877218]  r4:c08e546c
[   78.879783] [<c061f614>] (full_proxy_read) from [<c0489f10>] (vfs_read+0xc8/0x348)
[   78.887473]  r9:c80f7f68 r8:b6a5e000 r7:ffffe000 r6:c7ac6000 r5:00000000 r4:00020000
[   78.895329] [<c0489e48>] (vfs_read) from [<c048a574>] (ksys_read+0x74/0xf8)
[   78.902397]  r10:00000003 r9:c80f6000 r8:c0200204 r7:00000000 r6:00000000 r5:c7ac6000
[   78.910343]  r4:c7ac6000
[   78.912907] [<c048a500>] (ksys_read) from [<c048a610>] (sys_read+0x18/0x1c)
[   78.919975]  r7:00000003 r6:b6f51f50 r5:00020000 r4:b6a5e007
[   78.925714] [<c048a5f8>] (sys_read) from [<c0200040>] (ret_fast_syscall+0x0/0x2c)
[   78.933311] Exception stack(0xc80f7fa8 to 0xc80f7ff0)
[   78.938436] 7fa0:                   b6a5e007 00020000 00000003 b6a5e000 00020000 00000000
[   78.946736] 7fc0: b6a5e007 00020000 b6f51f50 00000003 00000003 00000000 00020000 be8aa614
[   78.955035] 7fe0: 00000003 be8aa360 b6ebc1e7 b6e42216
[   78.960159] Code: e5903000 e0833001 e5930000 f57ff04f (e89da800) 
[   78.966344] ---[ end trace 5aa6c15c853b219c ]---

It seems not the whole range as exposed by the DTB is mmapable.

        avs-monitor@7d5d2000 {
                compatible = "brcm,bcm2711-avs-monitor",
                             "syscon", "simple-mfd";
                reg = <0x7d5d2000 0xf00>;

                thermal: thermal {
                        compatible = "brcm,bcm2711-thermal";
                        #thermal-sensor-cells = <0>;
                };
        };