sim: Thermal support for Linux

This patch enables Linux to read the temperature using hwmon infrastructure.
In order to use this in your gem5 you need to compile the kernel using the
following configs:

CONFIG_HWMON=y
CONFIG_SENSORS_VEXPRESS=y

And a proper dts file (containing an entry such as):

dcc {
 compatible = "arm,vexpress,config-bus";
 arm,vexpress,config-bridge = <&v2m_sysreg>;

  temp@0 {
   compatible = "arm,vexpress-temp";
   arm,vexpress-sysreg,func = <4 0>;
   label = "DCC";
  };
};

src/dev/arm/RealView.py

@@ -129,6 +129,22 @@ class RealViewOsc(ClockDomain):
 
     freq = Param.Clock("Default frequency")
 
+class RealViewTemperatureSensor(SimObject):
+    type = 'RealViewTemperatureSensor'
+    cxx_header = "dev/arm/rv_ctrl.hh"
+
+    parent = Param.RealViewCtrl(Parent.any, "RealView controller")
+
+    system = Param.System(Parent.any, "system")
+
+    # See ARM DUI 0447J (ARM Motherboard Express uATX -- V2M-P1) and
+    # the individual core/logic tile reference manuals for details
+    # about the site/position/dcc/device allocation.
+    site = Param.UInt8("Board Site")
+    position = Param.UInt8("Position in device stack")
+    dcc = Param.UInt8("Daughterboard Configuration Controller")
+    device = Param.UInt8("Device ID")
+
 class VExpressMCC(SubSystem):
     """ARM V2M-P1 Motherboard Configuration Controller
 
@@ -140,11 +156,17 @@ Express (V2M-P1) motherboard. See ARM DUI 0447J for details.
     class Osc(RealViewOsc):
         site, position, dcc = (0, 0, 0)
 
+    class Temperature(RealViewTemperatureSensor):
+        site, position, dcc = (0, 0, 0)
+
     osc_mcc = Osc(device=0, freq="50MHz")
     osc_clcd = Osc(device=1, freq="23.75MHz")
     osc_peripheral = Osc(device=2, freq="24MHz")
     osc_system_bus = Osc(device=4, freq="24MHz")
 
+    # See Table 4.19 in ARM DUI 0447J (Motherboard Express uATX TRM).
+    temp_crtl = Temperature(device=0)
+
 class CoreTile2A15DCC(SubSystem):
     """ARM CoreTile Express A15x2 Daughterboard Configuration Controller
 

src/dev/arm/rv_ctrl.cc

@@ -37,11 +37,14 @@
  * Authors: Ali Saidi
  */
 
+#include "dev/arm/rv_ctrl.hh"
+
 #include "base/trace.hh"
 #include "debug/RVCTRL.hh"
-#include "dev/arm/rv_ctrl.hh"
 #include "mem/packet.hh"
 #include "mem/packet_access.hh"
+#include "sim/power/thermal_model.hh"
+#include "sim/system.hh"
 #include "sim/voltage_domain.hh"
 
 RealViewCtrl::RealViewCtrl(Params *p)
@@ -293,7 +296,21 @@ RealViewOsc::write(uint32_t freq)
     clockPeriod(SimClock::Float::s / freq);
 }
 
+uint32_t
+RealViewTemperatureSensor::read() const
+{
+    // Temperature reported in uC
+    ThermalModel * tm = system->getThermalModel();
+    if (tm) {
+        double t = tm->getTemp();
+        if (t < 0)
+            warn("Temperature below zero!\n");
+        return fmax(0, t) * 1000000;
+    }
 
+    // Report a dummy 25 degrees temperature
+    return 25000000;
+}
 
 RealViewCtrl *
 RealViewCtrlParams::create()
@@ -306,3 +323,9 @@ RealViewOscParams::create()
 {
     return new RealViewOsc(this);
 }
+
+RealViewTemperatureSensor *
+RealViewTemperatureSensorParams::create()
+{
+    return new RealViewTemperatureSensor(this);
+}

src/dev/arm/rv_ctrl.hh

@@ -44,6 +44,7 @@
 #include "dev/io_device.hh"
 #include "params/RealViewCtrl.hh"
 #include "params/RealViewOsc.hh"
+#include "params/RealViewTemperatureSensor.hh"
 
 /** @file
  * This implements the simple real view registers on a PBXA9
@@ -219,5 +220,32 @@ class RealViewOsc
     void clockPeriod(Tick clock_period);
 };
 
+/**
+ * This device implements the temperature sensor used in the
+ * RealView/Versatile Express platform.
+ *
+ * See ARM DUI 0447J (ARM  Motherboard Express uATX -- V2M-P1).
+ */
+class RealViewTemperatureSensor
+    : public SimObject, RealViewCtrl::Device
+{
+  public:
+    RealViewTemperatureSensor(RealViewTemperatureSensorParams *p)
+    : SimObject(p),
+      RealViewCtrl::Device(*p->parent, RealViewCtrl::FUNC_TEMP,
+                           p->site, p->position, p->dcc, p->device),
+      system(p->system)
+    {}
+    virtual ~RealViewTemperatureSensor() {};
+
+  public: // RealViewCtrl::Device interface
+    uint32_t read() const override;
+    void write(uint32_t temp) override {}
+
+  protected:
+    /** The system this RV device belongs to */
+    System * system;
+};
+
 
 #endif // __DEV_ARM_RV_HH__