1 /*
2  * ARM CMSDK APB watchdog emulation
3  *
4  * Copyright (c) 2018 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 "APB watchdog" which is part of the Cortex-M
14  * System Design Kit (CMSDK) and documented in the Cortex-M System
15  * Design Kit Technical Reference Manual (ARM DDI0479C):
16  * https://developer.arm.com/products/system-design/system-design-kits/cortex-m-system-design-kit
17  *
18  * We also support the variant of this device found in the TI
19  * Stellaris/Luminary boards and documented in:
20  * http://www.ti.com/lit/ds/symlink/lm3s6965.pdf
21  */
22 
23 #include "qemu/osdep.h"
24 #include "qemu/log.h"
25 #include "trace.h"
26 #include "qapi/error.h"
27 #include "qemu/module.h"
28 #include "sysemu/watchdog.h"
29 #include "hw/sysbus.h"
30 #include "hw/irq.h"
31 #include "hw/qdev-properties.h"
32 #include "hw/registerfields.h"
33 #include "hw/watchdog/cmsdk-apb-watchdog.h"
34 #include "migration/vmstate.h"
35 
36 REG32(WDOGLOAD, 0x0)
37 REG32(WDOGVALUE, 0x4)
38 REG32(WDOGCONTROL, 0x8)
39     FIELD(WDOGCONTROL, INTEN, 0, 1)
40     FIELD(WDOGCONTROL, RESEN, 1, 1)
41 #define R_WDOGCONTROL_VALID_MASK (R_WDOGCONTROL_INTEN_MASK | \
42                                   R_WDOGCONTROL_RESEN_MASK)
43 REG32(WDOGINTCLR, 0xc)
44 REG32(WDOGRIS, 0x10)
45     FIELD(WDOGRIS, INT, 0, 1)
46 REG32(WDOGMIS, 0x14)
47 REG32(WDOGTEST, 0x418) /* only in Stellaris/Luminary version of the device */
48 REG32(WDOGLOCK, 0xc00)
49 #define WDOG_UNLOCK_VALUE 0x1ACCE551
50 REG32(WDOGITCR, 0xf00)
51     FIELD(WDOGITCR, ENABLE, 0, 1)
52 #define R_WDOGITCR_VALID_MASK R_WDOGITCR_ENABLE_MASK
53 REG32(WDOGITOP, 0xf04)
54     FIELD(WDOGITOP, WDOGRES, 0, 1)
55     FIELD(WDOGITOP, WDOGINT, 1, 1)
56 #define R_WDOGITOP_VALID_MASK (R_WDOGITOP_WDOGRES_MASK | \
57                                R_WDOGITOP_WDOGINT_MASK)
58 REG32(PID4, 0xfd0)
59 REG32(PID5, 0xfd4)
60 REG32(PID6, 0xfd8)
61 REG32(PID7, 0xfdc)
62 REG32(PID0, 0xfe0)
63 REG32(PID1, 0xfe4)
64 REG32(PID2, 0xfe8)
65 REG32(PID3, 0xfec)
66 REG32(CID0, 0xff0)
67 REG32(CID1, 0xff4)
68 REG32(CID2, 0xff8)
69 REG32(CID3, 0xffc)
70 
71 /* PID/CID values */
72 static const uint32_t cmsdk_apb_watchdog_id[] = {
73     0x04, 0x00, 0x00, 0x00, /* PID4..PID7 */
74     0x24, 0xb8, 0x1b, 0x00, /* PID0..PID3 */
75     0x0d, 0xf0, 0x05, 0xb1, /* CID0..CID3 */
76 };
77 
78 static const uint32_t luminary_watchdog_id[] = {
79     0x00, 0x00, 0x00, 0x00, /* PID4..PID7 */
80     0x05, 0x18, 0x18, 0x01, /* PID0..PID3 */
81     0x0d, 0xf0, 0x05, 0xb1, /* CID0..CID3 */
82 };
83 
84 static bool cmsdk_apb_watchdog_intstatus(CMSDKAPBWatchdog *s)
85 {
86     /* Return masked interrupt status */
87     return s->intstatus && (s->control & R_WDOGCONTROL_INTEN_MASK);
88 }
89 
90 static bool cmsdk_apb_watchdog_resetstatus(CMSDKAPBWatchdog *s)
91 {
92     /* Return masked reset status */
93     return s->resetstatus && (s->control & R_WDOGCONTROL_RESEN_MASK);
94 }
95 
96 static void cmsdk_apb_watchdog_update(CMSDKAPBWatchdog *s)
97 {
98     bool wdogint;
99     bool wdogres;
100 
101     if (s->itcr) {
102         /*
103          * Not checking that !s->is_luminary since s->itcr can't be written
104          * when s->is_luminary in the first place.
105          */
106         wdogint = s->itop & R_WDOGITOP_WDOGINT_MASK;
107         wdogres = s->itop & R_WDOGITOP_WDOGRES_MASK;
108     } else {
109         wdogint = cmsdk_apb_watchdog_intstatus(s);
110         wdogres = cmsdk_apb_watchdog_resetstatus(s);
111     }
112 
113     qemu_set_irq(s->wdogint, wdogint);
114     if (wdogres) {
115         watchdog_perform_action();
116     }
117 }
118 
119 static uint64_t cmsdk_apb_watchdog_read(void *opaque, hwaddr offset,
120                                         unsigned size)
121 {
122     CMSDKAPBWatchdog *s = CMSDK_APB_WATCHDOG(opaque);
123     uint64_t r;
124 
125     switch (offset) {
126     case A_WDOGLOAD:
127         r = ptimer_get_limit(s->timer);
128         break;
129     case A_WDOGVALUE:
130         r = ptimer_get_count(s->timer);
131         break;
132     case A_WDOGCONTROL:
133         r = s->control;
134         break;
135     case A_WDOGRIS:
136         r = s->intstatus;
137         break;
138     case A_WDOGMIS:
139         r = cmsdk_apb_watchdog_intstatus(s);
140         break;
141     case A_WDOGLOCK:
142         r = s->lock;
143         break;
144     case A_WDOGITCR:
145         if (s->is_luminary) {
146             goto bad_offset;
147         }
148         r = s->itcr;
149         break;
150     case A_PID4 ... A_CID3:
151         r = s->id[(offset - A_PID4) / 4];
152         break;
153     case A_WDOGINTCLR:
154     case A_WDOGITOP:
155         if (s->is_luminary) {
156             goto bad_offset;
157         }
158         qemu_log_mask(LOG_GUEST_ERROR,
159                       "CMSDK APB watchdog read: read of WO offset %x\n",
160                       (int)offset);
161         r = 0;
162         break;
163     case A_WDOGTEST:
164         if (!s->is_luminary) {
165             goto bad_offset;
166         }
167         qemu_log_mask(LOG_UNIMP,
168                       "Luminary watchdog read: stall not implemented\n");
169         r = 0;
170         break;
171     default:
172 bad_offset:
173         qemu_log_mask(LOG_GUEST_ERROR,
174                       "CMSDK APB watchdog read: bad offset %x\n", (int)offset);
175         r = 0;
176         break;
177     }
178     trace_cmsdk_apb_watchdog_read(offset, r, size);
179     return r;
180 }
181 
182 static void cmsdk_apb_watchdog_write(void *opaque, hwaddr offset,
183                                      uint64_t value, unsigned size)
184 {
185     CMSDKAPBWatchdog *s = CMSDK_APB_WATCHDOG(opaque);
186 
187     trace_cmsdk_apb_watchdog_write(offset, value, size);
188 
189     if (s->lock && offset != A_WDOGLOCK) {
190         /* Write access is disabled via WDOGLOCK */
191         qemu_log_mask(LOG_GUEST_ERROR,
192                       "CMSDK APB watchdog write: write to locked watchdog\n");
193         return;
194     }
195 
196     switch (offset) {
197     case A_WDOGLOAD:
198         /*
199          * Reset the load value and the current count, and make sure
200          * we're counting.
201          */
202         ptimer_transaction_begin(s->timer);
203         ptimer_set_limit(s->timer, value, 1);
204         ptimer_run(s->timer, 0);
205         ptimer_transaction_commit(s->timer);
206         break;
207     case A_WDOGCONTROL:
208         if (s->is_luminary && 0 != (R_WDOGCONTROL_INTEN_MASK & s->control)) {
209             /*
210              * The Luminary version of this device ignores writes to
211              * this register after the guest has enabled interrupts
212              * (so they can only be disabled again via reset).
213              */
214             break;
215         }
216         s->control = value & R_WDOGCONTROL_VALID_MASK;
217         cmsdk_apb_watchdog_update(s);
218         break;
219     case A_WDOGINTCLR:
220         s->intstatus = 0;
221         ptimer_transaction_begin(s->timer);
222         ptimer_set_count(s->timer, ptimer_get_limit(s->timer));
223         ptimer_transaction_commit(s->timer);
224         cmsdk_apb_watchdog_update(s);
225         break;
226     case A_WDOGLOCK:
227         s->lock = (value != WDOG_UNLOCK_VALUE);
228         break;
229     case A_WDOGITCR:
230         if (s->is_luminary) {
231             goto bad_offset;
232         }
233         s->itcr = value & R_WDOGITCR_VALID_MASK;
234         cmsdk_apb_watchdog_update(s);
235         break;
236     case A_WDOGITOP:
237         if (s->is_luminary) {
238             goto bad_offset;
239         }
240         s->itop = value & R_WDOGITOP_VALID_MASK;
241         cmsdk_apb_watchdog_update(s);
242         break;
243     case A_WDOGVALUE:
244     case A_WDOGRIS:
245     case A_WDOGMIS:
246     case A_PID4 ... A_CID3:
247         qemu_log_mask(LOG_GUEST_ERROR,
248                       "CMSDK APB watchdog write: write to RO offset 0x%x\n",
249                       (int)offset);
250         break;
251     case A_WDOGTEST:
252         if (!s->is_luminary) {
253             goto bad_offset;
254         }
255         qemu_log_mask(LOG_UNIMP,
256                       "Luminary watchdog write: stall not implemented\n");
257         break;
258     default:
259 bad_offset:
260         qemu_log_mask(LOG_GUEST_ERROR,
261                       "CMSDK APB watchdog write: bad offset 0x%x\n",
262                       (int)offset);
263         break;
264     }
265 }
266 
267 static const MemoryRegionOps cmsdk_apb_watchdog_ops = {
268     .read = cmsdk_apb_watchdog_read,
269     .write = cmsdk_apb_watchdog_write,
270     .endianness = DEVICE_LITTLE_ENDIAN,
271     /* byte/halfword accesses are just zero-padded on reads and writes */
272     .impl.min_access_size = 4,
273     .impl.max_access_size = 4,
274     .valid.min_access_size = 1,
275     .valid.max_access_size = 4,
276 };
277 
278 static void cmsdk_apb_watchdog_tick(void *opaque)
279 {
280     CMSDKAPBWatchdog *s = CMSDK_APB_WATCHDOG(opaque);
281 
282     if (!s->intstatus) {
283         /* Count expired for the first time: raise interrupt */
284         s->intstatus = R_WDOGRIS_INT_MASK;
285     } else {
286         /* Count expired for the second time: raise reset and stop clock */
287         s->resetstatus = 1;
288         ptimer_stop(s->timer);
289     }
290     cmsdk_apb_watchdog_update(s);
291 }
292 
293 static void cmsdk_apb_watchdog_reset(DeviceState *dev)
294 {
295     CMSDKAPBWatchdog *s = CMSDK_APB_WATCHDOG(dev);
296 
297     trace_cmsdk_apb_watchdog_reset();
298     s->control = 0;
299     s->intstatus = 0;
300     s->lock = 0;
301     s->itcr = 0;
302     s->itop = 0;
303     s->resetstatus = 0;
304     /* Set the limit and the count */
305     ptimer_transaction_begin(s->timer);
306     ptimer_set_limit(s->timer, 0xffffffff, 1);
307     ptimer_run(s->timer, 0);
308     ptimer_transaction_commit(s->timer);
309 }
310 
311 static void cmsdk_apb_watchdog_init(Object *obj)
312 {
313     SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
314     CMSDKAPBWatchdog *s = CMSDK_APB_WATCHDOG(obj);
315 
316     memory_region_init_io(&s->iomem, obj, &cmsdk_apb_watchdog_ops,
317                           s, "cmsdk-apb-watchdog", 0x1000);
318     sysbus_init_mmio(sbd, &s->iomem);
319     sysbus_init_irq(sbd, &s->wdogint);
320 
321     s->is_luminary = false;
322     s->id = cmsdk_apb_watchdog_id;
323 }
324 
325 static void cmsdk_apb_watchdog_realize(DeviceState *dev, Error **errp)
326 {
327     CMSDKAPBWatchdog *s = CMSDK_APB_WATCHDOG(dev);
328 
329     if (s->wdogclk_frq == 0) {
330         error_setg(errp,
331                    "CMSDK APB watchdog: wdogclk-frq property must be set");
332         return;
333     }
334 
335     s->timer = ptimer_init(cmsdk_apb_watchdog_tick, s,
336                            PTIMER_POLICY_WRAP_AFTER_ONE_PERIOD |
337                            PTIMER_POLICY_TRIGGER_ONLY_ON_DECREMENT |
338                            PTIMER_POLICY_NO_IMMEDIATE_RELOAD |
339                            PTIMER_POLICY_NO_COUNTER_ROUND_DOWN);
340 
341     ptimer_transaction_begin(s->timer);
342     ptimer_set_freq(s->timer, s->wdogclk_frq);
343     ptimer_transaction_commit(s->timer);
344 }
345 
346 static const VMStateDescription cmsdk_apb_watchdog_vmstate = {
347     .name = "cmsdk-apb-watchdog",
348     .version_id = 1,
349     .minimum_version_id = 1,
350     .fields = (VMStateField[]) {
351         VMSTATE_PTIMER(timer, CMSDKAPBWatchdog),
352         VMSTATE_UINT32(control, CMSDKAPBWatchdog),
353         VMSTATE_UINT32(intstatus, CMSDKAPBWatchdog),
354         VMSTATE_UINT32(lock, CMSDKAPBWatchdog),
355         VMSTATE_UINT32(itcr, CMSDKAPBWatchdog),
356         VMSTATE_UINT32(itop, CMSDKAPBWatchdog),
357         VMSTATE_UINT32(resetstatus, CMSDKAPBWatchdog),
358         VMSTATE_END_OF_LIST()
359     }
360 };
361 
362 static Property cmsdk_apb_watchdog_properties[] = {
363     DEFINE_PROP_UINT32("wdogclk-frq", CMSDKAPBWatchdog, wdogclk_frq, 0),
364     DEFINE_PROP_END_OF_LIST(),
365 };
366 
367 static void cmsdk_apb_watchdog_class_init(ObjectClass *klass, void *data)
368 {
369     DeviceClass *dc = DEVICE_CLASS(klass);
370 
371     dc->realize = cmsdk_apb_watchdog_realize;
372     dc->vmsd = &cmsdk_apb_watchdog_vmstate;
373     dc->reset = cmsdk_apb_watchdog_reset;
374     device_class_set_props(dc, cmsdk_apb_watchdog_properties);
375 }
376 
377 static const TypeInfo cmsdk_apb_watchdog_info = {
378     .name = TYPE_CMSDK_APB_WATCHDOG,
379     .parent = TYPE_SYS_BUS_DEVICE,
380     .instance_size = sizeof(CMSDKAPBWatchdog),
381     .instance_init = cmsdk_apb_watchdog_init,
382     .class_init = cmsdk_apb_watchdog_class_init,
383 };
384 
385 static void luminary_watchdog_init(Object *obj)
386 {
387     CMSDKAPBWatchdog *s = CMSDK_APB_WATCHDOG(obj);
388 
389     s->is_luminary = true;
390     s->id = luminary_watchdog_id;
391 }
392 
393 static const TypeInfo luminary_watchdog_info = {
394     .name = TYPE_LUMINARY_WATCHDOG,
395     .parent = TYPE_CMSDK_APB_WATCHDOG,
396     .instance_init = luminary_watchdog_init
397 };
398 
399 static void cmsdk_apb_watchdog_register_types(void)
400 {
401     type_register_static(&cmsdk_apb_watchdog_info);
402     type_register_static(&luminary_watchdog_info);
403 }
404 
405 type_init(cmsdk_apb_watchdog_register_types);
406