uart8250.cc revision 12239 
1/*
2 * Copyright (c) 2005 The Regents of The University of Michigan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Ali Saidi
29 */
30
31/** @file
32 * Implements a 8250 UART
33 */
34
35#include "dev/serial/uart8250.hh"
36
37#include <string>
38#include <vector>
39
40#include "base/inifile.hh"
41#include "base/trace.hh"
42#include "config/the_isa.hh"
43#include "debug/Uart.hh"
44#include "dev/platform.hh"
45#include "mem/packet.hh"
46#include "mem/packet_access.hh"
47
48using namespace std;
49using namespace TheISA;
50
51void
52Uart8250::processIntrEvent(int intrBit)
53{
54    if (intrBit & IER) {
55       DPRINTF(Uart, "UART InterEvent, interrupting\n");
56       platform->postConsoleInt();
57       status |= intrBit;
58       lastTxInt = curTick();
59    }
60    else
61       DPRINTF(Uart, "UART InterEvent, not interrupting\n");
62
63}
64
65/* The linux serial driver (8250.c about line 1182) loops reading from
66 * the device until the device reports it has no more data to
67 * read. After a maximum of 255 iterations the code prints "serial8250
68 * too much work for irq X," and breaks out of the loop. Since the
69 * simulated system is so much slower than the actual system, if a
70 * user is typing on the keyboard it is very easy for them to provide
71 * input at a fast enough rate to not allow the loop to exit and thus
72 * the error to be printed. This magic number provides a delay between
73 * the time the UART receives a character to send to the simulated
74 * system and the time it actually notifies the system it has a
75 * character to send to alleviate this problem. --Ali
76 */
77void
78Uart8250::scheduleIntr(Event *event)
79{
80    static const Tick interval = 225 * SimClock::Int::ns;
81    DPRINTF(Uart, "Scheduling IER interrupt for %s, at cycle %lld\n",
82            event->name(), curTick() + interval);
83    if (!event->scheduled())
84        schedule(event, curTick() + interval);
85    else
86        reschedule(event, curTick() + interval);
87}
88
89
90Uart8250::Uart8250(const Params *p)
91    : Uart(p, 8), IER(0), DLAB(0), LCR(0), MCR(0), lastTxInt(0),
92      txIntrEvent([this]{ processIntrEvent(TX_INT); }, "TX"),
93      rxIntrEvent([this]{ processIntrEvent(RX_INT); }, "RX")
94{
95}
96
97Tick
98Uart8250::read(PacketPtr pkt)
99{
100    assert(pkt->getAddr() >= pioAddr && pkt->getAddr() < pioAddr + pioSize);
101    assert(pkt->getSize() == 1);
102
103    Addr daddr = pkt->getAddr() - pioAddr;
104
105    DPRINTF(Uart, " read register %#x\n", daddr);
106
107    switch (daddr) {
108        case 0x0:
109            if (!(LCR & 0x80)) { // read byte
110                if (device->dataAvailable())
111                    pkt->set(device->readData());
112                else {
113                    pkt->set((uint8_t)0);
114                    // A limited amount of these are ok.
115                    DPRINTF(Uart, "empty read of RX register\n");
116                }
117                status &= ~RX_INT;
118                platform->clearConsoleInt();
119
120                if (device->dataAvailable() && (IER & UART_IER_RDI))
121                    scheduleIntr(&rxIntrEvent);
122            } else { // dll divisor latch
123               ;
124            }
125            break;
126        case 0x1:
127            if (!(LCR & 0x80)) { // Intr Enable Register(IER)
128                pkt->set(IER);
129            } else { // DLM divisor latch MSB
130                ;
131            }
132            break;
133        case 0x2: // Intr Identification Register (IIR)
134            DPRINTF(Uart, "IIR Read, status = %#x\n", (uint32_t)status);
135
136            if (status & RX_INT) /* Rx data interrupt has a higher priority */
137                pkt->set(IIR_RXID);
138            else if (status & TX_INT) {
139                pkt->set(IIR_TXID);
140                //Tx interrupts are cleared on IIR reads
141                status &= ~TX_INT;
142            } else
143                pkt->set(IIR_NOPEND);
144
145            break;
146        case 0x3: // Line Control Register (LCR)
147            pkt->set(LCR);
148            break;
149        case 0x4: // Modem Control Register (MCR)
150            pkt->set(MCR);
151            break;
152        case 0x5: // Line Status Register (LSR)
153            uint8_t lsr;
154            lsr = 0;
155            // check if there are any bytes to be read
156            if (device->dataAvailable())
157                lsr = UART_LSR_DR;
158            lsr |= UART_LSR_TEMT | UART_LSR_THRE;
159            pkt->set(lsr);
160            break;
161        case 0x6: // Modem Status Register (MSR)
162            pkt->set((uint8_t)0);
163            break;
164        case 0x7: // Scratch Register (SCR)
165            pkt->set((uint8_t)0); // doesn't exist with at 8250.
166            break;
167        default:
168            panic("Tried to access a UART port that doesn't exist\n");
169            break;
170    }
171/*    uint32_t d32 = *data;
172    DPRINTF(Uart, "Register read to register %#x returned %#x\n", daddr, d32);
173*/
174    pkt->makeAtomicResponse();
175    return pioDelay;
176}
177
178Tick
179Uart8250::write(PacketPtr pkt)
180{
181
182    assert(pkt->getAddr() >= pioAddr && pkt->getAddr() < pioAddr + pioSize);
183    assert(pkt->getSize() == 1);
184
185    Addr daddr = pkt->getAddr() - pioAddr;
186
187    DPRINTF(Uart, " write register %#x value %#x\n", daddr, pkt->get<uint8_t>());
188
189    switch (daddr) {
190        case 0x0:
191            if (!(LCR & 0x80)) { // write byte
192                device->writeData(pkt->get<uint8_t>());
193                platform->clearConsoleInt();
194                status &= ~TX_INT;
195                if (UART_IER_THRI & IER)
196                    scheduleIntr(&txIntrEvent);
197            } else { // dll divisor latch
198               ;
199            }
200            break;
201        case 0x1:
202            if (!(LCR & 0x80)) { // Intr Enable Register(IER)
203                IER = pkt->get<uint8_t>();
204                if (UART_IER_THRI & IER)
205                {
206                    DPRINTF(Uart, "IER: IER_THRI set, scheduling TX intrrupt\n");
207                    if (curTick() - lastTxInt > 225 * SimClock::Int::ns) {
208                        DPRINTF(Uart, "-- Interrupting Immediately... %d,%d\n",
209                                curTick(), lastTxInt);
210                        txIntrEvent.process();
211                    } else {
212                        DPRINTF(Uart, "-- Delaying interrupt... %d,%d\n",
213                                curTick(), lastTxInt);
214                        scheduleIntr(&txIntrEvent);
215                    }
216                }
217                else
218                {
219                    DPRINTF(Uart, "IER: IER_THRI cleared, descheduling TX intrrupt\n");
220                    if (txIntrEvent.scheduled())
221                        deschedule(txIntrEvent);
222                    if (status & TX_INT)
223                        platform->clearConsoleInt();
224                    status &= ~TX_INT;
225                }
226
227                if ((UART_IER_RDI & IER) && device->dataAvailable()) {
228                    DPRINTF(Uart, "IER: IER_RDI set, scheduling RX intrrupt\n");
229                    scheduleIntr(&rxIntrEvent);
230                } else {
231                    DPRINTF(Uart, "IER: IER_RDI cleared, descheduling RX intrrupt\n");
232                    if (rxIntrEvent.scheduled())
233                        deschedule(rxIntrEvent);
234                    if (status & RX_INT)
235                        platform->clearConsoleInt();
236                    status &= ~RX_INT;
237                }
238             } else { // DLM divisor latch MSB
239                ;
240            }
241            break;
242        case 0x2: // FIFO Control Register (FCR)
243            break;
244        case 0x3: // Line Control Register (LCR)
245            LCR = pkt->get<uint8_t>();
246            break;
247        case 0x4: // Modem Control Register (MCR)
248            if (pkt->get<uint8_t>() == (UART_MCR_LOOP | 0x0A))
249                    MCR = 0x9A;
250            break;
251        case 0x7: // Scratch Register (SCR)
252            // We are emulating a 8250 so we don't have a scratch reg
253            break;
254        default:
255            panic("Tried to access a UART port that doesn't exist\n");
256            break;
257    }
258    pkt->makeAtomicResponse();
259    return pioDelay;
260}
261
262void
263Uart8250::dataAvailable()
264{
265    // if the kernel wants an interrupt when we have data
266    if (IER & UART_IER_RDI)
267    {
268        platform->postConsoleInt();
269        status |= RX_INT;
270    }
271
272}
273
274AddrRangeList
275Uart8250::getAddrRanges() const
276{
277    AddrRangeList ranges;
278    ranges.push_back(RangeSize(pioAddr, pioSize));
279    return ranges;
280}
281
282void
283Uart8250::serialize(CheckpointOut &cp) const
284{
285    SERIALIZE_SCALAR(status);
286    SERIALIZE_SCALAR(IER);
287    SERIALIZE_SCALAR(DLAB);
288    SERIALIZE_SCALAR(LCR);
289    SERIALIZE_SCALAR(MCR);
290    Tick rxintrwhen;
291    if (rxIntrEvent.scheduled())
292        rxintrwhen = rxIntrEvent.when();
293    else
294        rxintrwhen = 0;
295    Tick txintrwhen;
296    if (txIntrEvent.scheduled())
297        txintrwhen = txIntrEvent.when();
298    else
299        txintrwhen = 0;
300     SERIALIZE_SCALAR(rxintrwhen);
301     SERIALIZE_SCALAR(txintrwhen);
302}
303
304void
305Uart8250::unserialize(CheckpointIn &cp)
306{
307    UNSERIALIZE_SCALAR(status);
308    UNSERIALIZE_SCALAR(IER);
309    UNSERIALIZE_SCALAR(DLAB);
310    UNSERIALIZE_SCALAR(LCR);
311    UNSERIALIZE_SCALAR(MCR);
312    Tick rxintrwhen;
313    Tick txintrwhen;
314    UNSERIALIZE_SCALAR(rxintrwhen);
315    UNSERIALIZE_SCALAR(txintrwhen);
316    if (rxintrwhen != 0)
317        schedule(rxIntrEvent, rxintrwhen);
318    if (txintrwhen != 0)
319        schedule(txIntrEvent, txintrwhen);
320}
321
322Uart8250 *
323Uart8250Params::create()
324{
325    return new Uart8250(this);
326}
327