1/*
2 * Copyright (c) 2018 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder.  You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions are
16 * met: redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer;
18 * redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution;
21 * neither the name of the copyright holders nor the names of its
22 * contributors may be used to endorse or promote products derived from
23 * this software without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 *
37 * Authors: Matteo Andreozzi
38 */
39
40#include "turnaround_policy_ideal.hh"
41
42#include "params/QoSTurnaroundPolicyIdeal.hh"
43
44namespace QoS {
45
46TurnaroundPolicyIdeal::TurnaroundPolicyIdeal(const Params* p)
47  : TurnaroundPolicy(p)
48{}
49
50TurnaroundPolicyIdeal::~TurnaroundPolicyIdeal()
51{}
52
53MemCtrl::BusState
54TurnaroundPolicyIdeal::selectBusState()
55{
56    auto bus_state = memCtrl->getBusState();
57    const auto num_priorities = memCtrl->numPriorities();
58
59    // QoS-aware turnaround policy
60    // Loop for every queue in the memory controller.
61    for (uint8_t i = 0; i < num_priorities; i++) {
62
63        // Starting from top priority queues first
64        uint8_t queue_idx = num_priorities - i - 1;
65
66        const uint64_t readq_size = memCtrl->getReadQueueSize(queue_idx);
67        const uint64_t writeq_size = memCtrl->getWriteQueueSize(queue_idx);
68
69        // No data for current priority: both the read queue
70        // and write queue are empty.
71        if ((readq_size == 0) && (writeq_size == 0)) {
72            continue;
73        }
74
75        // Data found - select state
76        if (readq_size == 0) {
77            bus_state = MemCtrl::WRITE;
78        } else if (writeq_size == 0) {
79            bus_state = MemCtrl::READ;
80        } else {
81            // readq_size > 0 && writeq_size > 0
82            bus_state = ((memCtrl->getBusState() == MemCtrl::READ) ?
83                    MemCtrl::WRITE : MemCtrl::READ);
84        }
85
86        DPRINTF(QOS,
87                "QoSMemoryTurnaround::QoSTurnaroundPolicyIdeal - "
88                "QoS priority %d queues %d, %d triggering bus %s "
89                "in state %s\n", queue_idx, readq_size, writeq_size,
90                (bus_state != memCtrl->getBusState()) ?
91                "turnaround" : "staying",
92                (bus_state == MemCtrl::READ)? "READ" : "WRITE");
93        // State selected - exit loop
94        break;
95    }
96
97    return bus_state;
98}
99
100} // namespace QoS
101
102QoS::TurnaroundPolicyIdeal *
103QoSTurnaroundPolicyIdealParams::create()
104{
105    return new QoS::TurnaroundPolicyIdeal(this);
106}
107