summaryrefslogtreecommitdiffstats
path: root/platforms/chibios/drivers/serial_protocol.c
blob: c95aed988550d7a94fb8f4fa0a91a512a76a4898 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
// Copyright 2022 Stefan Kerkmann
// SPDX-License-Identifier: GPL-2.0-or-later

#include <ch.h>

#include "quantum.h"
#include "serial.h"
#include "serial_protocol.h"
#include "printf.h"
#include "synchronization_util.h"

static inline bool initiate_transaction(uint8_t transaction_id);
static inline bool react_to_transaction(void);

/**
 * @brief This thread runs on the slave and responds to transactions initiated
 * by the master.
 */
static THD_WORKING_AREA(waSlaveThread, 1024);
static THD_FUNCTION(SlaveThread, arg) {
    (void)arg;
    chRegSetThreadName("split_protocol_tx_rx");

    while (true) {
        if (unlikely(!react_to_transaction())) {
            /* Clear the receive queue, to start with a clean slate.
             * Parts of failed transactions or spurious bytes could still be in it. */
            serial_transport_driver_clear();
        }
    }
}

/**
 * @brief Slave specific initializations.
 */
void soft_serial_target_init(void) {
    serial_transport_driver_slave_init();

    /* Start transport thread. */
    chThdCreateStatic(waSlaveThread, sizeof(waSlaveThread), HIGHPRIO, SlaveThread, NULL);
}

/**
 * @brief Master specific initializations.
 */
void soft_serial_initiator_init(void) {
    serial_transport_driver_master_init();
}

/**
 * @brief React to transactions started by the master.
 */
static inline bool react_to_transaction(void) {
    uint8_t transaction_id = 0;
    /* Wait until there is a transaction for us. */
    if (unlikely(!serial_transport_receive_blocking(&transaction_id, sizeof(transaction_id)))) {
        return false;
    }

    /* Sanity check that we are actually responding to a valid transaction. */
    if (unlikely(transaction_id >= NUM_TOTAL_TRANSACTIONS)) {
        return false;
    }

    split_shared_memory_lock_autounlock();

    split_transaction_desc_t* transaction = &split_transaction_table[transaction_id];

    /* Send back the handshake which is XORed as a simple checksum,
     to signal that the slave is ready to receive possible transaction buffers  */
    transaction_id ^= NUM_TOTAL_TRANSACTIONS;
    if (unlikely(!serial_transport_send(&transaction_id, sizeof(transaction_id)))) {
        return false;
    }

    /* Receive transaction buffer from the master. If this transaction requires it.*/
    if (transaction->initiator2target_buffer_size) {
        if (unlikely(!serial_transport_receive(split_trans_initiator2target_buffer(transaction), transaction->initiator2target_buffer_size))) {
            return false;
        }
    }

    /* Allow any slave processing to occur. */
    if (transaction->slave_callback) {
        transaction->slave_callback(transaction->initiator2target_buffer_size, split_trans_initiator2target_buffer(transaction), transaction->initiator2target_buffer_size, split_trans_target2initiator_buffer(transaction));
    }

    /* Send transaction buffer to the master. If this transaction requires it. */
    if (transaction->target2initiator_buffer_size) {
        if (unlikely(!serial_transport_send(split_trans_target2initiator_buffer(transaction), transaction->target2initiator_buffer_size))) {
            return false;
        }
    }

    return true;
}

/**
 * @brief Start transaction from the master half to the slave half.
 *
 * @param index Transaction Table index of the transaction to start.
 * @return bool Indicates success of transaction.
 */
bool soft_serial_transaction(int index) {
    bool result = initiate_transaction((uint8_t)index);

    if (unlikely(!result)) {
        /* Clear the receive queue, to start with a clean slate.
         * Parts of failed transactions or spurious bytes could still be in it. */
        serial_transport_driver_clear();
    }

    return result;
}

/**
 * @brief Initiate transaction to slave half.
 */
static inline bool initiate_transaction(uint8_t transaction_id) {
    /* Sanity check that we are actually starting a valid transaction. */
    if (unlikely(transaction_id >= NUM_TOTAL_TRANSACTIONS)) {
        serial_dprintf("SPLIT: illegal transaction id\n");
        return false;
    }

    split_shared_memory_lock_autounlock();

    split_transaction_desc_t* transaction = &split_transaction_table[transaction_id];

    /* Send transaction table index to the slave, which doubles as basic handshake token. */
    if (unlikely(!serial_transport_send(&transaction_id, sizeof(transaction_id)))) {
        serial_dprintf("SPLIT: sending handshake failed\n");
        return false;
    }

    uint8_t transaction_id_shake = 0xFF;

    /* Which we always read back first so that we can error out correctly.
     *   - due to the half duplex limitations on return codes, we always have to read *something*.
     *   - without the read, write only transactions *always* succeed, even during the boot process where the slave is not ready.
     */
    if (unlikely(!serial_transport_receive(&transaction_id_shake, sizeof(transaction_id_shake)) || (transaction_id_shake != (transaction_id ^ NUM_TOTAL_TRANSACTIONS)))) {
        serial_dprintf("SPLIT: receiving handshake failed\n");
        return false;
    }

    /* Send transaction buffer to the slave. If this transaction requires it. */
    if (transaction->initiator2target_buffer_size) {
        if (unlikely(!serial_transport_send(split_trans_initiator2target_buffer(transaction), transaction->initiator2target_buffer_size))) {
            serial_dprintf("SPLIT: sending buffer failed\n");
            return false;
        }
    }

    /* Receive transaction buffer from the slave. If this transaction requires it. */
    if (transaction->target2initiator_buffer_size) {
        if (unlikely(!serial_transport_receive(split_trans_target2initiator_buffer(transaction), transaction->target2initiator_buffer_size))) {
            serial_dprintf("SPLIT: receiving buffer failed\n");
            return false;
        }
    }

    return true;
}