LXR qemu/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"
  38OBJECT_DECLARE_SIMPLE_TYPE(SSECounter, SSE_COUNTER)
  39
  40struct 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 */
  78uint64_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 */
  89uint64_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 */
 103void sse_counter_register_consumer(SSECounter *counter, Notifier *notifier);
 104
 105#endif
 106