Could not read operational registers value through 4-port usb3.0 host controller

Question

Problem Description:

Unable to observe updated values in PORTSC[0~3] registers of Fresco Logic FL1100 USB host controller using Python mmap on a Linux machine.

Observed Behavior:

Using setpci, BAR[0~3] addresses obtained successfully. PORTSC[0~3] offsets defined in datasheet. Mmap created to access registers. Register values remain constant (0xa0002a0) despite device connection/disconnection.

The code is the following:

def read_mmio_reg(bar_address, offset):

    
    # Extract the base address from the BAR value (Bits 31:4)
    base_address = (bar_address & 0xFFFFFFF0) >> 4

    # The size of the memory region you want to map
    region_size = 4096  # Adjust this based on your requirements

    # Open /dev/mem for memory mapping (requires elevated permissions)
    with open('/dev/mem', 'r+b') as mem_file:
        # Map the memory region into the process's address space
        mmapped_data = mmap.mmap(mem_file.fileno(), region_size, offset=base_address)

        # Now, you can access the Host Controller Operational registers within the mapped memory
        # For example, read a 32-bit value from offset 0x10 within the mapped region
        #offset = 0x10
        register_value = int.from_bytes(mmapped_data[offset:offset + 4], byteorder='little')

        # Print the value
        print("Value at offset {0} = {1}:".format(offset,hex(register_value)))

        # Don't forget to unmap the memory when you're done
        mmapped_data.close()
        return register_value

• The offsets are correct per datasheet.
• mmap function can open with read/write permissions (PROT_READ | PROT_WRITE).