xref: /openbmc/qemu/include/hw/timer/sse-counter.h (revision 19418584)
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
106