Virtual address VS physical address VS bus address

    In a computer with MMU, what the CPU sees is a virtual address, which is converted to a physical address after being sent to the MMU, and the virtual address is converted to a bus address through the corresponding circuit, which is the address seen by the peripheral.
    Therefore, the address seen by the DMA peripheral is actually the bus address

    Virtual->physical virt_to_phys()
    physical->virtual ioremap()

    Virtual->bus virt_to_bus()
    bus->virtual bus_to_virt()