I have the same issue on an Asus Radeon RX-550[1] and amdgpu.

The fan is on all the time.
By default pwm1_enable shows 1, however, even when I write 2 to it nothing
changes.

Interestingly enough, `fan1_input` reports no such device, whereas, temp1_input
seems to show the right temp. This seems to be corroborated by the sensors
output where temp is correctly reported but not fan speed.

[root@MS-7885 hwmon0]# pwd
/sys/devices/pci0000:00/0000:00:03.0/0000:03:00.0/hwmon/hwmon0

[root@MS-7885 hwmon0]# cat temp1_input && echo && sensors
32000

amdgpu-pci-0300
Adapter: PCI adapter
fan1:             N/A
temp1:        +32.0°C  (crit =  +0.0°C, hyst =  +0.0°C)
...

[1]:
03:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Lexa
PRO [Radeon RX 550] (rev c7) (prog-if 00 [VGA controller])
        Subsystem: ASUSTeK Computer Inc. Device 0513
        Physical Slot: 4
        Flags: bus master, fast devsel, latency 0, IRQ 37, NUMA node 0
        Memory at e0000000 (64-bit, prefetchable) [size=256M]
        Memory at f0000000 (64-bit, prefetchable) [size=2M]
        I/O ports at e000 [size=256]
        Memory at fbe00000 (32-bit, non-prefetchable) [size=256K]
        Expansion ROM at 000c0000 [disabled] [size=128K]
        Capabilities: [48] Vendor Specific Information: Len=08 <?>
        Capabilities: [50] Power Management version 3
        Capabilities: [58] Express Legacy Endpoint, MSI 00
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010
<?>
        Capabilities: [150] Advanced Error Reporting
        Capabilities: [200] #15
        Capabilities: [270] #19
        Capabilities: [2b0] Address Translation Service (ATS)
        Capabilities: [2c0] Page Request Interface (PRI)
        Capabilities: [2d0] Process Address Space ID (PASID)
        Capabilities: [320] Latency Tolerance Reporting
        Capabilities: [328] Alternative Routing-ID Interpretation (ARI)
        Capabilities: [370] L1 PM Substates
        Kernel driver in use: amdgpu
        Kernel modules: amdgpu