xref: /openbmc/qemu/hw/net/npcm7xx_emc.c (revision 0fbb5d2d)
1 /*
2  * Nuvoton NPCM7xx EMC Module
3  *
4  * Copyright 2020 Google LLC
5  *
6  * This program is free software; you can redistribute it and/or modify it
7  * under the terms of the GNU General Public License as published by the
8  * Free Software Foundation; either version 2 of the License, or
9  * (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14  * for more details.
15  *
16  * Unsupported/unimplemented features:
17  * - MCMDR.FDUP (full duplex) is ignored, half duplex is not supported
18  * - Only CAM0 is supported, CAM[1-15] are not
19  *   - writes to CAMEN.[1-15] are ignored, these bits always read as zeroes
20  * - MII is not implemented, MIIDA.BUSY and MIID always return zero
21  * - MCMDR.LBK is not implemented
22  * - MCMDR.{OPMOD,ENSQE,AEP,ARP} are not supported
23  * - H/W FIFOs are not supported, MCMDR.FFTCR is ignored
24  * - MGSTA.SQE is not supported
25  * - pause and control frames are not implemented
26  * - MGSTA.CCNT is not supported
27  * - MPCNT, DMARFS are not implemented
28  */
29 
30 #include "qemu/osdep.h"
31 
32 /* For crc32 */
33 #include <zlib.h>
34 
35 #include "qemu-common.h"
36 #include "hw/irq.h"
37 #include "hw/qdev-clock.h"
38 #include "hw/qdev-properties.h"
39 #include "hw/net/npcm7xx_emc.h"
40 #include "net/eth.h"
41 #include "migration/vmstate.h"
42 #include "qemu/bitops.h"
43 #include "qemu/error-report.h"
44 #include "qemu/log.h"
45 #include "qemu/module.h"
46 #include "qemu/units.h"
47 #include "sysemu/dma.h"
48 #include "trace.h"
49 
50 #define CRC_LENGTH 4
51 
52 /*
53  * The maximum size of a (layer 2) ethernet frame as defined by 802.3.
54  * 1518 = 6(dest macaddr) + 6(src macaddr) + 2(proto) + 4(crc) + 1500(payload)
55  * This does not include an additional 4 for the vlan field (802.1q).
56  */
57 #define MAX_ETH_FRAME_SIZE 1518
58 
59 static const char *emc_reg_name(int regno)
60 {
61 #define REG(name) case REG_ ## name: return #name;
62     switch (regno) {
63     REG(CAMCMR)
64     REG(CAMEN)
65     REG(TXDLSA)
66     REG(RXDLSA)
67     REG(MCMDR)
68     REG(MIID)
69     REG(MIIDA)
70     REG(FFTCR)
71     REG(TSDR)
72     REG(RSDR)
73     REG(DMARFC)
74     REG(MIEN)
75     REG(MISTA)
76     REG(MGSTA)
77     REG(MPCNT)
78     REG(MRPC)
79     REG(MRPCC)
80     REG(MREPC)
81     REG(DMARFS)
82     REG(CTXDSA)
83     REG(CTXBSA)
84     REG(CRXDSA)
85     REG(CRXBSA)
86     case REG_CAMM_BASE + 0: return "CAM0M";
87     case REG_CAML_BASE + 0: return "CAM0L";
88     case REG_CAMM_BASE + 2 ... REG_CAMML_LAST:
89         /* Only CAM0 is supported, fold the others into something simple. */
90         if (regno & 1) {
91             return "CAM<n>L";
92         } else {
93             return "CAM<n>M";
94         }
95     default: return "UNKNOWN";
96     }
97 #undef REG
98 }
99 
100 static void emc_reset(NPCM7xxEMCState *emc)
101 {
102     trace_npcm7xx_emc_reset(emc->emc_num);
103 
104     memset(&emc->regs[0], 0, sizeof(emc->regs));
105 
106     /* These regs have non-zero reset values. */
107     emc->regs[REG_TXDLSA] = 0xfffffffc;
108     emc->regs[REG_RXDLSA] = 0xfffffffc;
109     emc->regs[REG_MIIDA] = 0x00900000;
110     emc->regs[REG_FFTCR] = 0x0101;
111     emc->regs[REG_DMARFC] = 0x0800;
112     emc->regs[REG_MPCNT] = 0x7fff;
113 
114     emc->tx_active = false;
115     emc->rx_active = false;
116 }
117 
118 static void npcm7xx_emc_reset(DeviceState *dev)
119 {
120     NPCM7xxEMCState *emc = NPCM7XX_EMC(dev);
121     emc_reset(emc);
122 }
123 
124 static void emc_soft_reset(NPCM7xxEMCState *emc)
125 {
126     /*
127      * The docs say at least MCMDR.{LBK,OPMOD} bits are not changed during a
128      * soft reset, but does not go into further detail. For now, KISS.
129      */
130     uint32_t mcmdr = emc->regs[REG_MCMDR];
131     emc_reset(emc);
132     emc->regs[REG_MCMDR] = mcmdr & (REG_MCMDR_LBK | REG_MCMDR_OPMOD);
133 
134     qemu_set_irq(emc->tx_irq, 0);
135     qemu_set_irq(emc->rx_irq, 0);
136 }
137 
138 static void emc_set_link(NetClientState *nc)
139 {
140     /* Nothing to do yet. */
141 }
142 
143 /* MISTA.TXINTR is the union of the individual bits with their enables. */
144 static void emc_update_mista_txintr(NPCM7xxEMCState *emc)
145 {
146     /* Only look at the bits we support. */
147     uint32_t mask = (REG_MISTA_TXBERR |
148                      REG_MISTA_TDU |
149                      REG_MISTA_TXCP);
150     if (emc->regs[REG_MISTA] & emc->regs[REG_MIEN] & mask) {
151         emc->regs[REG_MISTA] |= REG_MISTA_TXINTR;
152     } else {
153         emc->regs[REG_MISTA] &= ~REG_MISTA_TXINTR;
154     }
155 }
156 
157 /* MISTA.RXINTR is the union of the individual bits with their enables. */
158 static void emc_update_mista_rxintr(NPCM7xxEMCState *emc)
159 {
160     /* Only look at the bits we support. */
161     uint32_t mask = (REG_MISTA_RXBERR |
162                      REG_MISTA_RDU |
163                      REG_MISTA_RXGD);
164     if (emc->regs[REG_MISTA] & emc->regs[REG_MIEN] & mask) {
165         emc->regs[REG_MISTA] |= REG_MISTA_RXINTR;
166     } else {
167         emc->regs[REG_MISTA] &= ~REG_MISTA_RXINTR;
168     }
169 }
170 
171 /* N.B. emc_update_mista_txintr must have already been called. */
172 static void emc_update_tx_irq(NPCM7xxEMCState *emc)
173 {
174     int level = !!(emc->regs[REG_MISTA] &
175                    emc->regs[REG_MIEN] &
176                    REG_MISTA_TXINTR);
177     trace_npcm7xx_emc_update_tx_irq(level);
178     qemu_set_irq(emc->tx_irq, level);
179 }
180 
181 /* N.B. emc_update_mista_rxintr must have already been called. */
182 static void emc_update_rx_irq(NPCM7xxEMCState *emc)
183 {
184     int level = !!(emc->regs[REG_MISTA] &
185                    emc->regs[REG_MIEN] &
186                    REG_MISTA_RXINTR);
187     trace_npcm7xx_emc_update_rx_irq(level);
188     qemu_set_irq(emc->rx_irq, level);
189 }
190 
191 /* Update IRQ states due to changes in MIEN,MISTA. */
192 static void emc_update_irq_from_reg_change(NPCM7xxEMCState *emc)
193 {
194     emc_update_mista_txintr(emc);
195     emc_update_tx_irq(emc);
196 
197     emc_update_mista_rxintr(emc);
198     emc_update_rx_irq(emc);
199 }
200 
201 static int emc_read_tx_desc(dma_addr_t addr, NPCM7xxEMCTxDesc *desc)
202 {
203     if (dma_memory_read(&address_space_memory, addr, desc,
204                         sizeof(*desc), MEMTXATTRS_UNSPECIFIED)) {
205         qemu_log_mask(LOG_GUEST_ERROR, "%s: Failed to read descriptor @ 0x%"
206                       HWADDR_PRIx "\n", __func__, addr);
207         return -1;
208     }
209     desc->flags = le32_to_cpu(desc->flags);
210     desc->txbsa = le32_to_cpu(desc->txbsa);
211     desc->status_and_length = le32_to_cpu(desc->status_and_length);
212     desc->ntxdsa = le32_to_cpu(desc->ntxdsa);
213     return 0;
214 }
215 
216 static int emc_write_tx_desc(const NPCM7xxEMCTxDesc *desc, dma_addr_t addr)
217 {
218     NPCM7xxEMCTxDesc le_desc;
219 
220     le_desc.flags = cpu_to_le32(desc->flags);
221     le_desc.txbsa = cpu_to_le32(desc->txbsa);
222     le_desc.status_and_length = cpu_to_le32(desc->status_and_length);
223     le_desc.ntxdsa = cpu_to_le32(desc->ntxdsa);
224     if (dma_memory_write(&address_space_memory, addr, &le_desc,
225                          sizeof(le_desc), MEMTXATTRS_UNSPECIFIED)) {
226         qemu_log_mask(LOG_GUEST_ERROR, "%s: Failed to write descriptor @ 0x%"
227                       HWADDR_PRIx "\n", __func__, addr);
228         return -1;
229     }
230     return 0;
231 }
232 
233 static int emc_read_rx_desc(dma_addr_t addr, NPCM7xxEMCRxDesc *desc)
234 {
235     if (dma_memory_read(&address_space_memory, addr, desc,
236                         sizeof(*desc), MEMTXATTRS_UNSPECIFIED)) {
237         qemu_log_mask(LOG_GUEST_ERROR, "%s: Failed to read descriptor @ 0x%"
238                       HWADDR_PRIx "\n", __func__, addr);
239         return -1;
240     }
241     desc->status_and_length = le32_to_cpu(desc->status_and_length);
242     desc->rxbsa = le32_to_cpu(desc->rxbsa);
243     desc->reserved = le32_to_cpu(desc->reserved);
244     desc->nrxdsa = le32_to_cpu(desc->nrxdsa);
245     return 0;
246 }
247 
248 static int emc_write_rx_desc(const NPCM7xxEMCRxDesc *desc, dma_addr_t addr)
249 {
250     NPCM7xxEMCRxDesc le_desc;
251 
252     le_desc.status_and_length = cpu_to_le32(desc->status_and_length);
253     le_desc.rxbsa = cpu_to_le32(desc->rxbsa);
254     le_desc.reserved = cpu_to_le32(desc->reserved);
255     le_desc.nrxdsa = cpu_to_le32(desc->nrxdsa);
256     if (dma_memory_write(&address_space_memory, addr, &le_desc,
257                          sizeof(le_desc), MEMTXATTRS_UNSPECIFIED)) {
258         qemu_log_mask(LOG_GUEST_ERROR, "%s: Failed to write descriptor @ 0x%"
259                       HWADDR_PRIx "\n", __func__, addr);
260         return -1;
261     }
262     return 0;
263 }
264 
265 static void emc_set_mista(NPCM7xxEMCState *emc, uint32_t flags)
266 {
267     trace_npcm7xx_emc_set_mista(flags);
268     emc->regs[REG_MISTA] |= flags;
269     if (extract32(flags, 16, 16)) {
270         emc_update_mista_txintr(emc);
271     }
272     if (extract32(flags, 0, 16)) {
273         emc_update_mista_rxintr(emc);
274     }
275 }
276 
277 static void emc_halt_tx(NPCM7xxEMCState *emc, uint32_t mista_flag)
278 {
279     emc->tx_active = false;
280     emc_set_mista(emc, mista_flag);
281 }
282 
283 static void emc_halt_rx(NPCM7xxEMCState *emc, uint32_t mista_flag)
284 {
285     emc->rx_active = false;
286     emc_set_mista(emc, mista_flag);
287 }
288 
289 static void emc_enable_rx_and_flush(NPCM7xxEMCState *emc)
290 {
291     emc->rx_active = true;
292     qemu_flush_queued_packets(qemu_get_queue(emc->nic));
293 }
294 
295 static void emc_set_next_tx_descriptor(NPCM7xxEMCState *emc,
296                                        const NPCM7xxEMCTxDesc *tx_desc,
297                                        uint32_t desc_addr)
298 {
299     /* Update the current descriptor, if only to reset the owner flag. */
300     if (emc_write_tx_desc(tx_desc, desc_addr)) {
301         /*
302          * We just read it so this shouldn't generally happen.
303          * Error already reported.
304          */
305         emc_set_mista(emc, REG_MISTA_TXBERR);
306     }
307     emc->regs[REG_CTXDSA] = TX_DESC_NTXDSA(tx_desc->ntxdsa);
308 }
309 
310 static void emc_set_next_rx_descriptor(NPCM7xxEMCState *emc,
311                                        const NPCM7xxEMCRxDesc *rx_desc,
312                                        uint32_t desc_addr)
313 {
314     /* Update the current descriptor, if only to reset the owner flag. */
315     if (emc_write_rx_desc(rx_desc, desc_addr)) {
316         /*
317          * We just read it so this shouldn't generally happen.
318          * Error already reported.
319          */
320         emc_set_mista(emc, REG_MISTA_RXBERR);
321     }
322     emc->regs[REG_CRXDSA] = RX_DESC_NRXDSA(rx_desc->nrxdsa);
323 }
324 
325 static void emc_try_send_next_packet(NPCM7xxEMCState *emc)
326 {
327     /* Working buffer for sending out packets. Most packets fit in this. */
328 #define TX_BUFFER_SIZE 2048
329     uint8_t tx_send_buffer[TX_BUFFER_SIZE];
330     uint32_t desc_addr = TX_DESC_NTXDSA(emc->regs[REG_CTXDSA]);
331     NPCM7xxEMCTxDesc tx_desc;
332     uint32_t next_buf_addr, length;
333     uint8_t *buf;
334     g_autofree uint8_t *malloced_buf = NULL;
335 
336     if (emc_read_tx_desc(desc_addr, &tx_desc)) {
337         /* Error reading descriptor, already reported. */
338         emc_halt_tx(emc, REG_MISTA_TXBERR);
339         emc_update_tx_irq(emc);
340         return;
341     }
342 
343     /* Nothing we can do if we don't own the descriptor. */
344     if (!(tx_desc.flags & TX_DESC_FLAG_OWNER_MASK)) {
345         trace_npcm7xx_emc_cpu_owned_desc(desc_addr);
346         emc_halt_tx(emc, REG_MISTA_TDU);
347         emc_update_tx_irq(emc);
348         return;
349      }
350 
351     /* Give the descriptor back regardless of what happens. */
352     tx_desc.flags &= ~TX_DESC_FLAG_OWNER_MASK;
353     tx_desc.status_and_length &= 0xffff;
354 
355     /*
356      * Despite the h/w documentation saying the tx buffer is word aligned,
357      * the linux driver does not word align the buffer. There is value in not
358      * aligning the buffer: See the description of NET_IP_ALIGN in linux
359      * kernel sources.
360      */
361     next_buf_addr = tx_desc.txbsa;
362     emc->regs[REG_CTXBSA] = next_buf_addr;
363     length = TX_DESC_PKT_LEN(tx_desc.status_and_length);
364     buf = &tx_send_buffer[0];
365 
366     if (length > sizeof(tx_send_buffer)) {
367         malloced_buf = g_malloc(length);
368         buf = malloced_buf;
369     }
370 
371     if (dma_memory_read(&address_space_memory, next_buf_addr, buf,
372                         length, MEMTXATTRS_UNSPECIFIED)) {
373         qemu_log_mask(LOG_GUEST_ERROR, "%s: Failed to read packet @ 0x%x\n",
374                       __func__, next_buf_addr);
375         emc_set_mista(emc, REG_MISTA_TXBERR);
376         emc_set_next_tx_descriptor(emc, &tx_desc, desc_addr);
377         emc_update_tx_irq(emc);
378         trace_npcm7xx_emc_tx_done(emc->regs[REG_CTXDSA]);
379         return;
380     }
381 
382     if ((tx_desc.flags & TX_DESC_FLAG_PADEN) && (length < MIN_PACKET_LENGTH)) {
383         memset(buf + length, 0, MIN_PACKET_LENGTH - length);
384         length = MIN_PACKET_LENGTH;
385     }
386 
387     /* N.B. emc_receive can get called here. */
388     qemu_send_packet(qemu_get_queue(emc->nic), buf, length);
389     trace_npcm7xx_emc_sent_packet(length);
390 
391     tx_desc.status_and_length |= TX_DESC_STATUS_TXCP;
392     if (tx_desc.flags & TX_DESC_FLAG_INTEN) {
393         emc_set_mista(emc, REG_MISTA_TXCP);
394     }
395     if (emc->regs[REG_MISTA] & emc->regs[REG_MIEN] & REG_MISTA_TXINTR) {
396         tx_desc.status_and_length |= TX_DESC_STATUS_TXINTR;
397     }
398 
399     emc_set_next_tx_descriptor(emc, &tx_desc, desc_addr);
400     emc_update_tx_irq(emc);
401     trace_npcm7xx_emc_tx_done(emc->regs[REG_CTXDSA]);
402 }
403 
404 static bool emc_can_receive(NetClientState *nc)
405 {
406     NPCM7xxEMCState *emc = NPCM7XX_EMC(qemu_get_nic_opaque(nc));
407 
408     bool can_receive = emc->rx_active;
409     trace_npcm7xx_emc_can_receive(can_receive);
410     return can_receive;
411 }
412 
413 /* If result is false then *fail_reason contains the reason. */
414 static bool emc_receive_filter1(NPCM7xxEMCState *emc, const uint8_t *buf,
415                                 size_t len, const char **fail_reason)
416 {
417     eth_pkt_types_e pkt_type = get_eth_packet_type(PKT_GET_ETH_HDR(buf));
418 
419     switch (pkt_type) {
420     case ETH_PKT_BCAST:
421         if (emc->regs[REG_CAMCMR] & REG_CAMCMR_CCAM) {
422             return true;
423         } else {
424             *fail_reason = "Broadcast packet disabled";
425             return !!(emc->regs[REG_CAMCMR] & REG_CAMCMR_ABP);
426         }
427     case ETH_PKT_MCAST:
428         if (emc->regs[REG_CAMCMR] & REG_CAMCMR_CCAM) {
429             return true;
430         } else {
431             *fail_reason = "Multicast packet disabled";
432             return !!(emc->regs[REG_CAMCMR] & REG_CAMCMR_AMP);
433         }
434     case ETH_PKT_UCAST: {
435         bool matches;
436         if (emc->regs[REG_CAMCMR] & REG_CAMCMR_AUP) {
437             return true;
438         }
439         matches = ((emc->regs[REG_CAMCMR] & REG_CAMCMR_ECMP) &&
440                    /* We only support one CAM register, CAM0. */
441                    (emc->regs[REG_CAMEN] & (1 << 0)) &&
442                    memcmp(buf, emc->conf.macaddr.a, ETH_ALEN) == 0);
443         if (emc->regs[REG_CAMCMR] & REG_CAMCMR_CCAM) {
444             *fail_reason = "MACADDR matched, comparison complemented";
445             return !matches;
446         } else {
447             *fail_reason = "MACADDR didn't match";
448             return matches;
449         }
450     }
451     default:
452         g_assert_not_reached();
453     }
454 }
455 
456 static bool emc_receive_filter(NPCM7xxEMCState *emc, const uint8_t *buf,
457                                size_t len)
458 {
459     const char *fail_reason = NULL;
460     bool ok = emc_receive_filter1(emc, buf, len, &fail_reason);
461     if (!ok) {
462         trace_npcm7xx_emc_packet_filtered_out(fail_reason);
463     }
464     return ok;
465 }
466 
467 static ssize_t emc_receive(NetClientState *nc, const uint8_t *buf, size_t len1)
468 {
469     NPCM7xxEMCState *emc = NPCM7XX_EMC(qemu_get_nic_opaque(nc));
470     const uint32_t len = len1;
471     size_t max_frame_len;
472     bool long_frame;
473     uint32_t desc_addr;
474     NPCM7xxEMCRxDesc rx_desc;
475     uint32_t crc;
476     uint8_t *crc_ptr;
477     uint32_t buf_addr;
478 
479     trace_npcm7xx_emc_receiving_packet(len);
480 
481     if (!emc_can_receive(nc)) {
482         qemu_log_mask(LOG_GUEST_ERROR, "%s: Unexpected packet\n", __func__);
483         return -1;
484     }
485 
486     if (len < ETH_HLEN ||
487         /* Defensive programming: drop unsupportable large packets. */
488         len > 0xffff - CRC_LENGTH) {
489         qemu_log_mask(LOG_GUEST_ERROR, "%s: Dropped frame of %u bytes\n",
490                       __func__, len);
491         return len;
492     }
493 
494     /*
495      * DENI is set if EMC received the Length/Type field of the incoming
496      * packet, so it will be set regardless of what happens next.
497      */
498     emc_set_mista(emc, REG_MISTA_DENI);
499 
500     if (!emc_receive_filter(emc, buf, len)) {
501         emc_update_rx_irq(emc);
502         return len;
503     }
504 
505     /* Huge frames (> DMARFC) are dropped. */
506     max_frame_len = REG_DMARFC_RXMS(emc->regs[REG_DMARFC]);
507     if (len + CRC_LENGTH > max_frame_len) {
508         trace_npcm7xx_emc_packet_dropped(len);
509         emc_set_mista(emc, REG_MISTA_DFOI);
510         emc_update_rx_irq(emc);
511         return len;
512     }
513 
514     /*
515      * Long Frames (> MAX_ETH_FRAME_SIZE) are also dropped, unless MCMDR.ALP
516      * is set.
517      */
518     long_frame = false;
519     if (len + CRC_LENGTH > MAX_ETH_FRAME_SIZE) {
520         if (emc->regs[REG_MCMDR] & REG_MCMDR_ALP) {
521             long_frame = true;
522         } else {
523             trace_npcm7xx_emc_packet_dropped(len);
524             emc_set_mista(emc, REG_MISTA_PTLE);
525             emc_update_rx_irq(emc);
526             return len;
527         }
528     }
529 
530     desc_addr = RX_DESC_NRXDSA(emc->regs[REG_CRXDSA]);
531     if (emc_read_rx_desc(desc_addr, &rx_desc)) {
532         /* Error reading descriptor, already reported. */
533         emc_halt_rx(emc, REG_MISTA_RXBERR);
534         emc_update_rx_irq(emc);
535         return len;
536     }
537 
538     /* Nothing we can do if we don't own the descriptor. */
539     if (!(rx_desc.status_and_length & RX_DESC_STATUS_OWNER_MASK)) {
540         trace_npcm7xx_emc_cpu_owned_desc(desc_addr);
541         emc_halt_rx(emc, REG_MISTA_RDU);
542         emc_update_rx_irq(emc);
543         return len;
544     }
545 
546     crc = 0;
547     crc_ptr = (uint8_t *) &crc;
548     if (!(emc->regs[REG_MCMDR] & REG_MCMDR_SPCRC)) {
549         crc = cpu_to_be32(crc32(~0, buf, len));
550     }
551 
552     /* Give the descriptor back regardless of what happens. */
553     rx_desc.status_and_length &= ~RX_DESC_STATUS_OWNER_MASK;
554 
555     buf_addr = rx_desc.rxbsa;
556     emc->regs[REG_CRXBSA] = buf_addr;
557     if (dma_memory_write(&address_space_memory, buf_addr, buf,
558                          len, MEMTXATTRS_UNSPECIFIED) ||
559         (!(emc->regs[REG_MCMDR] & REG_MCMDR_SPCRC) &&
560          dma_memory_write(&address_space_memory, buf_addr + len,
561                           crc_ptr, 4, MEMTXATTRS_UNSPECIFIED))) {
562         qemu_log_mask(LOG_GUEST_ERROR, "%s: Bus error writing packet\n",
563                       __func__);
564         emc_set_mista(emc, REG_MISTA_RXBERR);
565         emc_set_next_rx_descriptor(emc, &rx_desc, desc_addr);
566         emc_update_rx_irq(emc);
567         trace_npcm7xx_emc_rx_done(emc->regs[REG_CRXDSA]);
568         return len;
569     }
570 
571     trace_npcm7xx_emc_received_packet(len);
572 
573     /* Note: We've already verified len+4 <= 0xffff. */
574     rx_desc.status_and_length = len;
575     if (!(emc->regs[REG_MCMDR] & REG_MCMDR_SPCRC)) {
576         rx_desc.status_and_length += 4;
577     }
578     rx_desc.status_and_length |= RX_DESC_STATUS_RXGD;
579     emc_set_mista(emc, REG_MISTA_RXGD);
580 
581     if (emc->regs[REG_MISTA] & emc->regs[REG_MIEN] & REG_MISTA_RXINTR) {
582         rx_desc.status_and_length |= RX_DESC_STATUS_RXINTR;
583     }
584     if (long_frame) {
585         rx_desc.status_and_length |= RX_DESC_STATUS_PTLE;
586     }
587 
588     emc_set_next_rx_descriptor(emc, &rx_desc, desc_addr);
589     emc_update_rx_irq(emc);
590     trace_npcm7xx_emc_rx_done(emc->regs[REG_CRXDSA]);
591     return len;
592 }
593 
594 static uint64_t npcm7xx_emc_read(void *opaque, hwaddr offset, unsigned size)
595 {
596     NPCM7xxEMCState *emc = opaque;
597     uint32_t reg = offset / sizeof(uint32_t);
598     uint32_t result;
599 
600     if (reg >= NPCM7XX_NUM_EMC_REGS) {
601         qemu_log_mask(LOG_GUEST_ERROR,
602                       "%s: Invalid offset 0x%04" HWADDR_PRIx "\n",
603                       __func__, offset);
604         return 0;
605     }
606 
607     switch (reg) {
608     case REG_MIID:
609         /*
610          * We don't implement MII. For determinism, always return zero as
611          * writes record the last value written for debugging purposes.
612          */
613         qemu_log_mask(LOG_UNIMP, "%s: Read of MIID, returning 0\n", __func__);
614         result = 0;
615         break;
616     case REG_TSDR:
617     case REG_RSDR:
618         qemu_log_mask(LOG_GUEST_ERROR,
619                       "%s: Read of write-only reg, %s/%d\n",
620                       __func__, emc_reg_name(reg), reg);
621         return 0;
622     default:
623         result = emc->regs[reg];
624         break;
625     }
626 
627     trace_npcm7xx_emc_reg_read(emc->emc_num, result, emc_reg_name(reg), reg);
628     return result;
629 }
630 
631 static void npcm7xx_emc_write(void *opaque, hwaddr offset,
632                               uint64_t v, unsigned size)
633 {
634     NPCM7xxEMCState *emc = opaque;
635     uint32_t reg = offset / sizeof(uint32_t);
636     uint32_t value = v;
637 
638     g_assert(size == sizeof(uint32_t));
639 
640     if (reg >= NPCM7XX_NUM_EMC_REGS) {
641         qemu_log_mask(LOG_GUEST_ERROR,
642                       "%s: Invalid offset 0x%04" HWADDR_PRIx "\n",
643                       __func__, offset);
644         return;
645     }
646 
647     trace_npcm7xx_emc_reg_write(emc->emc_num, emc_reg_name(reg), reg, value);
648 
649     switch (reg) {
650     case REG_CAMCMR:
651         emc->regs[reg] = value;
652         break;
653     case REG_CAMEN:
654         /* Only CAM0 is supported, don't pretend otherwise. */
655         if (value & ~1) {
656             qemu_log_mask(LOG_GUEST_ERROR,
657                           "%s: Only CAM0 is supported, cannot enable others"
658                           ": 0x%x\n",
659                           __func__, value);
660         }
661         emc->regs[reg] = value & 1;
662         break;
663     case REG_CAMM_BASE + 0:
664         emc->regs[reg] = value;
665         emc->conf.macaddr.a[0] = value >> 24;
666         emc->conf.macaddr.a[1] = value >> 16;
667         emc->conf.macaddr.a[2] = value >> 8;
668         emc->conf.macaddr.a[3] = value >> 0;
669         break;
670     case REG_CAML_BASE + 0:
671         emc->regs[reg] = value;
672         emc->conf.macaddr.a[4] = value >> 24;
673         emc->conf.macaddr.a[5] = value >> 16;
674         break;
675     case REG_MCMDR: {
676         uint32_t prev;
677         if (value & REG_MCMDR_SWR) {
678             emc_soft_reset(emc);
679             /* On h/w the reset happens over multiple cycles. For now KISS. */
680             break;
681         }
682         prev = emc->regs[reg];
683         emc->regs[reg] = value;
684         /* Update tx state. */
685         if (!(prev & REG_MCMDR_TXON) &&
686             (value & REG_MCMDR_TXON)) {
687             emc->regs[REG_CTXDSA] = emc->regs[REG_TXDLSA];
688             /*
689              * Linux kernel turns TX on with CPU still holding descriptor,
690              * which suggests we should wait for a write to TSDR before trying
691              * to send a packet: so we don't send one here.
692              */
693         } else if ((prev & REG_MCMDR_TXON) &&
694                    !(value & REG_MCMDR_TXON)) {
695             emc->regs[REG_MGSTA] |= REG_MGSTA_TXHA;
696         }
697         if (!(value & REG_MCMDR_TXON)) {
698             emc_halt_tx(emc, 0);
699         }
700         /* Update rx state. */
701         if (!(prev & REG_MCMDR_RXON) &&
702             (value & REG_MCMDR_RXON)) {
703             emc->regs[REG_CRXDSA] = emc->regs[REG_RXDLSA];
704         } else if ((prev & REG_MCMDR_RXON) &&
705                    !(value & REG_MCMDR_RXON)) {
706             emc->regs[REG_MGSTA] |= REG_MGSTA_RXHA;
707         }
708         if (value & REG_MCMDR_RXON) {
709             emc_enable_rx_and_flush(emc);
710         } else {
711             emc_halt_rx(emc, 0);
712         }
713         break;
714     }
715     case REG_TXDLSA:
716     case REG_RXDLSA:
717     case REG_DMARFC:
718     case REG_MIID:
719         emc->regs[reg] = value;
720         break;
721     case REG_MIEN:
722         emc->regs[reg] = value;
723         emc_update_irq_from_reg_change(emc);
724         break;
725     case REG_MISTA:
726         /* Clear the bits that have 1 in "value". */
727         emc->regs[reg] &= ~value;
728         emc_update_irq_from_reg_change(emc);
729         break;
730     case REG_MGSTA:
731         /* Clear the bits that have 1 in "value". */
732         emc->regs[reg] &= ~value;
733         break;
734     case REG_TSDR:
735         if (emc->regs[REG_MCMDR] & REG_MCMDR_TXON) {
736             emc->tx_active = true;
737             /* Keep trying to send packets until we run out. */
738             while (emc->tx_active) {
739                 emc_try_send_next_packet(emc);
740             }
741         }
742         break;
743     case REG_RSDR:
744         if (emc->regs[REG_MCMDR] & REG_MCMDR_RXON) {
745             emc_enable_rx_and_flush(emc);
746         }
747         break;
748     case REG_MIIDA:
749         emc->regs[reg] = value & ~REG_MIIDA_BUSY;
750         break;
751     case REG_MRPC:
752     case REG_MRPCC:
753     case REG_MREPC:
754     case REG_CTXDSA:
755     case REG_CTXBSA:
756     case REG_CRXDSA:
757     case REG_CRXBSA:
758         qemu_log_mask(LOG_GUEST_ERROR,
759                       "%s: Write to read-only reg %s/%d\n",
760                       __func__, emc_reg_name(reg), reg);
761         break;
762     default:
763         qemu_log_mask(LOG_UNIMP, "%s: Write to unimplemented reg %s/%d\n",
764                       __func__, emc_reg_name(reg), reg);
765         break;
766     }
767 }
768 
769 static const struct MemoryRegionOps npcm7xx_emc_ops = {
770     .read = npcm7xx_emc_read,
771     .write = npcm7xx_emc_write,
772     .endianness = DEVICE_LITTLE_ENDIAN,
773     .valid = {
774         .min_access_size = 4,
775         .max_access_size = 4,
776         .unaligned = false,
777     },
778 };
779 
780 static void emc_cleanup(NetClientState *nc)
781 {
782     /* Nothing to do yet. */
783 }
784 
785 static NetClientInfo net_npcm7xx_emc_info = {
786     .type = NET_CLIENT_DRIVER_NIC,
787     .size = sizeof(NICState),
788     .can_receive = emc_can_receive,
789     .receive = emc_receive,
790     .cleanup = emc_cleanup,
791     .link_status_changed = emc_set_link,
792 };
793 
794 static void npcm7xx_emc_realize(DeviceState *dev, Error **errp)
795 {
796     NPCM7xxEMCState *emc = NPCM7XX_EMC(dev);
797     SysBusDevice *sbd = SYS_BUS_DEVICE(emc);
798 
799     memory_region_init_io(&emc->iomem, OBJECT(emc), &npcm7xx_emc_ops, emc,
800                           TYPE_NPCM7XX_EMC, 4 * KiB);
801     sysbus_init_mmio(sbd, &emc->iomem);
802     sysbus_init_irq(sbd, &emc->tx_irq);
803     sysbus_init_irq(sbd, &emc->rx_irq);
804 
805     qemu_macaddr_default_if_unset(&emc->conf.macaddr);
806     emc->nic = qemu_new_nic(&net_npcm7xx_emc_info, &emc->conf,
807                             object_get_typename(OBJECT(dev)), dev->id, emc);
808     qemu_format_nic_info_str(qemu_get_queue(emc->nic), emc->conf.macaddr.a);
809 }
810 
811 static void npcm7xx_emc_unrealize(DeviceState *dev)
812 {
813     NPCM7xxEMCState *emc = NPCM7XX_EMC(dev);
814 
815     qemu_del_nic(emc->nic);
816 }
817 
818 static const VMStateDescription vmstate_npcm7xx_emc = {
819     .name = TYPE_NPCM7XX_EMC,
820     .version_id = 0,
821     .minimum_version_id = 0,
822     .fields = (VMStateField[]) {
823         VMSTATE_UINT8(emc_num, NPCM7xxEMCState),
824         VMSTATE_UINT32_ARRAY(regs, NPCM7xxEMCState, NPCM7XX_NUM_EMC_REGS),
825         VMSTATE_BOOL(tx_active, NPCM7xxEMCState),
826         VMSTATE_BOOL(rx_active, NPCM7xxEMCState),
827         VMSTATE_END_OF_LIST(),
828     },
829 };
830 
831 static Property npcm7xx_emc_properties[] = {
832     DEFINE_NIC_PROPERTIES(NPCM7xxEMCState, conf),
833     DEFINE_PROP_END_OF_LIST(),
834 };
835 
836 static void npcm7xx_emc_class_init(ObjectClass *klass, void *data)
837 {
838     DeviceClass *dc = DEVICE_CLASS(klass);
839 
840     set_bit(DEVICE_CATEGORY_NETWORK, dc->categories);
841     dc->desc = "NPCM7xx EMC Controller";
842     dc->realize = npcm7xx_emc_realize;
843     dc->unrealize = npcm7xx_emc_unrealize;
844     dc->reset = npcm7xx_emc_reset;
845     dc->vmsd = &vmstate_npcm7xx_emc;
846     device_class_set_props(dc, npcm7xx_emc_properties);
847 }
848 
849 static const TypeInfo npcm7xx_emc_info = {
850     .name = TYPE_NPCM7XX_EMC,
851     .parent = TYPE_SYS_BUS_DEVICE,
852     .instance_size = sizeof(NPCM7xxEMCState),
853     .class_init = npcm7xx_emc_class_init,
854 };
855 
856 static void npcm7xx_emc_register_type(void)
857 {
858     type_register_static(&npcm7xx_emc_info);
859 }
860 
861 type_init(npcm7xx_emc_register_type)
862