include/hw/timer/armv7m_systick.h

   1 /*
   2  * ARMv7M SysTick timer
   3  *
   4  * Copyright (c) 2006-2007 CodeSourcery.
   5  * Written by Paul Brook
   6  * Copyright (c) 2017 Linaro Ltd
   7  * Written by Peter Maydell
   8  *
   9  * This code is licensed under the GPL (version 2 or later).
  10  */
  11
  12 #ifndef HW_TIMER_ARMV7M_SYSTICK_H
  13 #define HW_TIMER_ARMV7M_SYSTICK_H
  14
  15 #include "hw/sysbus.h"
  16
  17 #define TYPE_SYSTICK "armv7m_systick"
  18
  19 #define SYSTICK(obj) OBJECT_CHECK(SysTickState, (obj), TYPE_SYSTICK)
  20
  21 typedef struct SysTickState {
  22     /*< private >*/
  23     SysBusDevice parent_obj;
  24     /*< public >*/
  25
  26     uint32_t control;
  27     uint32_t reload;
  28     int64_t tick;
  29     QEMUTimer *timer;
  30     MemoryRegion iomem;
  31     qemu_irq irq;
  32 } SysTickState;
  33
  34 /*
  35  * Multiplication factor to convert from system clock ticks to qemu timer
  36  * ticks. This should be set (by board code, usually) to a value
  37  * equal to NANOSECONDS_PER_SECOND / frq, where frq is the clock frequency
  38  * in Hz of the CPU.
  39  *
  40  * This value is used by the systick device when it is running in
  41  * its "use the CPU clock" mode (ie when SYST_CSR.CLKSOURCE == 1) to
  42  * set how fast the timer should tick.
  43  *
  44  * TODO: we should refactor this so that rather than using a global
  45  * we use a device property or something similar. This is complicated
  46  * because (a) the property would need to be plumbed through from the
  47  * board code down through various layers to the systick device
  48  * and (b) the property needs to be modifiable after realize, because
  49  * the stellaris board uses this to implement the behaviour where the
  50  * guest can reprogram the PLL registers to downclock the CPU, and the
  51  * systick device needs to react accordingly. Possibly this should
  52  * be deferred until we have a good API for modelling clock trees.
  53  */
  54 extern int system_clock_scale;
  55
  56 #endif