gem5/src/dev/arm/GenericTimer.py

# Copyright (c) 2009-2020 ARM Limited
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from m5.SimObject import SimObject
from m5.objects.Device import PioDevice
from m5.params import Param, MaxAddr, NULL, VectorParam
from m5.proxy import Parent
from m5.util import fatal
from m5.util.fdthelper import FdtNode, FdtProperty, FdtPropertyWords, FdtState

class SystemCounter(SimObject):
    """
Shared by both PE-implementations and memory-mapped timers. It provides a
uniform view of system time through its counter value.

Reference:
    Arm ARM (ARM DDI 0487E.a)
    D11.1.2 - The system counter
    """

    type = 'SystemCounter'
    cxx_header = "dev/arm/generic_timer.hh"
    cxx_class = 'gem5::SystemCounter'

    # Maximum of 1004 frequency entries, including end marker
    freqs = VectorParam.UInt32([0x01800000], "Frequencies available for the "
        "system counter (in Hz). First element is the base frequency, "
        "following are alternative lower ones which must be exact divisors")

    def generateDtb(self):
        if not self.freqs:
            fatal("No counter frequency to expose in DTB")
        return FdtPropertyWords("clock-frequency", [self.freqs[0]])

class GenericTimer(SimObject):
    """
Architected timers per PE in the system. Each of them provides a physical
counter, a virtual counter and several timers accessible from different
exception levels and security states.

Reference:
    Arm ARM (ARM DDI 0487E.a)
    D11.2 - The AArch64 view of the Generic Timer
    G6.2  - The AArch32 view of the Generic Timer
    """

    type = 'GenericTimer'
    cxx_header = "dev/arm/generic_timer.hh"
    cxx_class = 'gem5::GenericTimer'

    _freq_in_dtb = False

    system = Param.ArmSystem(Parent.any, "system")

    counter = Param.SystemCounter(Parent.any, "Global system counter")

    int_phys_s = Param.ArmPPI("Physical (S) timer interrupt")
    int_phys_ns = Param.ArmPPI("Physical (NS) timer interrupt")
    int_virt = Param.ArmPPI("Virtual timer interrupt")
    int_hyp = Param.ArmPPI("Hypervisor timer interrupt")

    # This value should be in theory initialized by the highest
    # priviledged software. We do this in gem5 to avoid KVM
    # complications (the gem5 firmware won't run at highest EL)
    #
    # PLEASE note: change this parameter only if using the gem5 bootloader
    # Another real world bootloader might be changing the CNTFRQ register
    # value, so this initial value will be discarded
    cntfrq = Param.UInt64(0x1800000, "Value for the CNTFRQ timer register")

    def generateDeviceTree(self, state):
        node = FdtNode("timer")

        node.appendCompatible(["arm,cortex-a15-timer",
                               "arm,armv7-timer",
                               "arm,armv8-timer"])

        gic = self._parent.unproxy(self).gic
        node.append(FdtPropertyWords("interrupts",
            self.int_phys_s.generateFdtProperty(gic) +
            self.int_phys_ns.generateFdtProperty(gic) +
            self.int_virt.generateFdtProperty(gic) +
            self.int_hyp.generateFdtProperty(gic)))

        if self._freq_in_dtb:
            node.append(self.counter.unproxy(self).generateDtb())

        yield node

class GenericTimerFrame(PioDevice):
    """
Memory-mapped timer frame implementation. Controlled from GenericTimerMem,
may be used by peripherals without a system register interface.

Reference:
    Arm ARM (ARM DDI 0487E.a)
    I2.3.2 - The CNTBaseN and CNTEL0BaseN frames
    """

    type = 'GenericTimerFrame'
    cxx_header = "dev/arm/generic_timer.hh"
    cxx_class = 'gem5::GenericTimerFrame'

    _frame_num = 0

    counter = Param.SystemCounter(Parent.any, "Global system counter")

    cnt_base = Param.Addr("CNTBase register frame base")
    cnt_el0_base = Param.Addr(MaxAddr, "CNTEL0Base register frame base")

    int_phys = Param.ArmSPI("Physical Interrupt")
    int_virt = Param.ArmSPI("Virtual Interrupt")

    def generateDeviceTree(self, state, gic):
        node = FdtNode("frame@{:08x}".format(self.cnt_base.value))
        node.append(FdtPropertyWords("frame-number", self._frame_num))

        ints = self.int_phys.generateFdtProperty(gic)
        if self.int_virt != NULL:
            ints.extend(self.int_virt.generateFdtProperty(gic))
        node.append(FdtPropertyWords("interrupts", ints))

        reg = state.addrCells(self.cnt_base) + state.sizeCells(0x1000)
        if self.cnt_el0_base.value != MaxAddr:
            reg.extend(state.addrCells(self.cnt_el0_base)
                       + state.sizeCells(0x1000))
        node.append(FdtPropertyWords("reg", reg))

        return node

class GenericTimerMem(PioDevice):
    """
System level implementation. It provides three main components:
- Memory-mapped counter module: controls the system timer through the
  CNTControlBase frame, and provides its value through the CNTReadBase frame
- Memory-mapped timer control module: controls the memory-mapped timers
- Memory-mapped timers: implementations of the GenericTimer for system
  peripherals

Reference:
    Arm ARM (ARM DDI 0487E.a)
    I2 - System Level Implementation of the Generic Timer
    """

    type = 'GenericTimerMem'
    cxx_header = "dev/arm/generic_timer.hh"
    cxx_class = 'gem5::GenericTimerMem'

    _freq_in_dtb = False

    counter = Param.SystemCounter(Parent.any, "Global system counter")

    cnt_control_base = Param.Addr("CNTControlBase register frame base")
    cnt_read_base = Param.Addr("CNTReadBase register frame base")
    cnt_ctl_base = Param.Addr("CNTCTLBase register frame base")

    # Maximum of 8 timer frames
    frames = VectorParam.GenericTimerFrame([], "Memory-mapped timer frames")

    def generateDeviceTree(self, state):
        node = self.generateBasicPioDeviceNode(state, "timer",
            self.cnt_ctl_base, 0x1000)
        node.appendCompatible(["arm,armv7-timer-mem"])
        node.append(state.addrCellsProperty())
        node.append(state.sizeCellsProperty())
        node.append(FdtProperty("ranges"))

        if self._freq_in_dtb:
            node.append(self.counter.unproxy(self).generateDtb())

        gic = self._parent.unproxy(self).gic

        for i, frame in enumerate(self.frames):
            frame._frame_num = i
            node.append(frame.generateDeviceTree(state, gic))

        yield node