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 #include "qom/object.h"
  17
  18 #define TYPE_SYSTICK "armv7m_systick"
  19
  20 typedef struct SysTickState SysTickState;
  21 DECLARE_INSTANCE_CHECKER(SysTickState, SYSTICK,
  22                          TYPE_SYSTICK)
  23
  24 struct SysTickState {
  25     /*< private >*/
  26     SysBusDevice parent_obj;
  27     /*< public >*/
  28
  29     uint32_t control;
  30     uint32_t reload;
  31     int64_t tick;
  32     QEMUTimer *timer;
  33     MemoryRegion iomem;
  34     qemu_irq irq;
  35 };
  36
  37 /*
  38  * Multiplication factor to convert from system clock ticks to qemu timer
  39  * ticks. This should be set (by board code, usually) to a value
  40  * equal to NANOSECONDS_PER_SECOND / frq, where frq is the clock frequency
  41  * in Hz of the CPU.
  42  *
  43  * This value is used by the systick device when it is running in
  44  * its "use the CPU clock" mode (ie when SYST_CSR.CLKSOURCE == 1) to
  45  * set how fast the timer should tick.
  46  *
  47  * TODO: we should refactor this so that rather than using a global
  48  * we use a device property or something similar. This is complicated
  49  * because (a) the property would need to be plumbed through from the
  50  * board code down through various layers to the systick device
  51  * and (b) the property needs to be modifiable after realize, because
  52  * the stellaris board uses this to implement the behaviour where the
  53  * guest can reprogram the PLL registers to downclock the CPU, and the
  54  * systick device needs to react accordingly. Possibly this should
  55  * be deferred until we have a good API for modelling clock trees.
  56  */
  57 extern int system_clock_scale;
  58
  59 #endif