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sse-counter.h (3271B)

      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