MosChip PCIe serial port adapter is disabled and stops working some time after boot

Issue

lspci -vv while working:

02:00.0 Serial controller: MosChip Semiconductor Technology Ltd. 4-Port PCIe Serial Adapter (prog-if 02 [16550])
        Subsystem: Device a000:1000
        Flags: bus master, fast devsel, latency 0, IRQ 19
        I/O ports at e030 [size=8]
        Memory at f7c07000 (32-bit, non-prefetchable) [size=4K]
        Memory at f7c06000 (32-bit, non-prefetchable) [size=4K]
        Capabilities: [50] MSI: Enable- Count=1/8 Maskable- 64bit+
        Capabilities: [78] Power Management version 3
        Capabilities: [80] Express Legacy Endpoint, MSI 00
        Capabilities: [100] Virtual Channel
        Capabilities: [800] Advanced Error Reporting
        Kernel driver in use: serial

and after it stops working:

02:00.0 Serial controller: MosChip Semiconductor Technology Ltd. 4-Port PCIe Serial Adapter (prog-if 02 [16550])
        Subsystem: Device a000:1000
        Flags: fast devsel, IRQ 19
        I/O ports at e030 [disabled] [size=8]
        [virtual] Memory at f7c07000 (32-bit, non-prefetchable) [size=4K]
        [virtual] Memory at f7c06000 (32-bit, non-prefetchable) [size=4K]
        Capabilities: [50] MSI: Enable- Count=1/8 Maskable- 64bit+
        Capabilities: [78] Power Management version 3
        Capabilities: [80] Express Legacy Endpoint, MSI 00
        Capabilities: [100] Virtual Channel
        Capabilities: [800] Advanced Error Reporting
        Kernel driver in use: serial