include/hw/timer/sse-counter.h

   1 /*
   2  * Arm SSE Subsystem System Counter
   3  *
   4  * Copyright (c) 2020 Linaro Limited
   5  * Written by Peter Maydell
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 or
   9  * (at your option) any later version.
  10  */
  11
  12 /*
  13  * This is a model of the "System counter" which is documented in
  14  * the Arm SSE-123 Example Subsystem Technical Reference Manual:
  15  * https://developer.arm.com/documentation/101370/latest/
  16  *
  17  * QEMU interface:
  18  *  + Clock input "CLK": clock
  19  *  + sysbus MMIO region 0: the control register frame
  20  *  + sysbus MMIO region 1: the status register frame
  21  *
  22  * Consumers of the system counter's timestamp, such as the SSE
  23  * System Timer device, can also use the APIs sse_counter_for_timestamp(),
  24  * sse_counter_tick_to_time() and sse_counter_register_consumer() to
  25  * interact with an instance of the System Counter. Generally the
  26  * consumer device should have a QOM link property which the board
  27  * code can set to the appropriate instance of the system counter.
  28  */
  29
  30 #ifndef SSE_COUNTER_H
  31 #define SSE_COUNTER_H
  32
  33 #include "hw/sysbus.h"
  34 #include "qom/object.h"
  35 #include "qemu/notify.h"
  36
  37 #define TYPE_SSE_COUNTER "sse-counter"
  38 OBJECT_DECLARE_SIMPLE_TYPE(SSECounter, SSE_COUNTER)
  39
  40 struct SSECounter {
  41     /*< private >*/
  42     SysBusDevice parent_obj;
  43
  44     /*< public >*/
  45     MemoryRegion control_mr;
  46     MemoryRegion status_mr;
  47     Clock *clk;
  48     NotifierList notifier_list;
  49
  50     uint32_t cntcr;
  51     uint32_t cntscr0;
  52
  53     /*
  54      * These are used for handling clock frequency changes: they are a
  55      * tuple of (QEMU_CLOCK_VIRTUAL timestamp, CNTCV at that time),
  56      * taken when the clock frequency changes. sse_cntcv() needs them
  57      * to calculate the current CNTCV.
  58      */
  59     uint64_t ns_then;
  60     uint64_t ticks_then;
  61 };
  62
  63 /*
  64  * These functions are the interface by which a consumer of
  65  * the system timestamp (such as the SSE system timer device)
  66  * can communicate with the SSECounter.
  67  */
  68
  69 /**
  70  * sse_counter_for_timestamp:
  71  * @counter: SSECounter
  72  * @ns: timestamp of QEMU_CLOCK_VIRTUAL in nanoseconds
  73  *
  74  * Returns the value of the timestamp counter at the specified
  75  * point in time (assuming that no changes to scale factor, enable, etc
  76  * happen in the meantime).
  77  */
  78 uint64_t sse_counter_for_timestamp(SSECounter *counter, uint64_t ns);
  79
  80 /**
  81  * sse_counter_tick_to_time:
  82  * @counter: SSECounter
  83  * @tick: tick value
  84  *
  85  * Returns the time (a QEMU_CLOCK_VIRTUAL timestamp in nanoseconds)
  86  * when the timestamp counter will reach the specified tick count.
  87  * If the counter is not currently running, returns UINT64_MAX.
  88  */
  89 uint64_t sse_counter_tick_to_time(SSECounter *counter, uint64_t tick);
  90
  91 /**
  92  * sse_counter_register_consumer:
  93  * @counter: SSECounter
  94  * @notifier: Notifier which is notified on counter changes
  95  *
  96  * Registers @notifier with the SSECounter. When the counter's
  97  * configuration changes in a way that might invalidate information
  98  * previously returned via sse_counter_for_timestamp() or
  99  * sse_counter_tick_to_time(), the notifier will be called.
 100  * Devices which consume the timestamp counter can use this as
 101  * a cue to recalculate timer events.
 102  */
 103 void sse_counter_register_consumer(SSECounter *counter, Notifier *notifier);
 104
 105 #endif