1/*-
2 * Copyright (c) 2000, 2001 Michael Smith
3 * Copyright (c) 2000 BSDi
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28#include <sys/cdefs.h>
| 1/*-
2 * Copyright (c) 2000, 2001 Michael Smith
3 * Copyright (c) 2000 BSDi
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28#include <sys/cdefs.h>
|
44#include <dev/acpica/acpivar.h>
45#include <dev/pci/pcivar.h>
46
47/*
48 * A timecounter based on the free-running ACPI timer.
49 *
50 * Based on the i386-only mp_clock.c by <phk@FreeBSD.ORG>.
51 */
52
53/* Hooks for the ACPI CA debugging infrastructure */
54#define _COMPONENT ACPI_TIMER
55ACPI_MODULE_NAME("TIMER")
56
57static device_t acpi_timer_dev;
58static struct resource *acpi_timer_reg;
59static bus_space_handle_t acpi_timer_bsh;
60static bus_space_tag_t acpi_timer_bst;
61
62static u_int acpi_timer_frequency = 14318182 / 4;
63
64static void acpi_timer_identify(driver_t *driver, device_t parent);
65static int acpi_timer_probe(device_t dev);
66static int acpi_timer_attach(device_t dev);
67static u_int acpi_timer_get_timecount(struct timecounter *tc);
68static u_int acpi_timer_get_timecount_safe(struct timecounter *tc);
69static int acpi_timer_sysctl_freq(SYSCTL_HANDLER_ARGS);
70static void acpi_timer_boot_test(void);
71
72static u_int acpi_timer_read(void);
73static int acpi_timer_test(void);
74
75static device_method_t acpi_timer_methods[] = {
76 DEVMETHOD(device_identify, acpi_timer_identify),
77 DEVMETHOD(device_probe, acpi_timer_probe),
78 DEVMETHOD(device_attach, acpi_timer_attach),
79
80 {0, 0}
81};
82
83static driver_t acpi_timer_driver = {
84 "acpi_timer",
85 acpi_timer_methods,
86 0,
87};
88
89static devclass_t acpi_timer_devclass;
90DRIVER_MODULE(acpi_timer, acpi, acpi_timer_driver, acpi_timer_devclass, 0, 0);
91MODULE_DEPEND(acpi_timer, acpi, 1, 1, 1);
92
93static struct timecounter acpi_timer_timecounter = {
94 acpi_timer_get_timecount_safe, /* get_timecount function */
95 0, /* no poll_pps */
96 0, /* no default counter_mask */
97 0, /* no default frequency */
98 "ACPI", /* name */
99 1000 /* quality */
100};
101
102static u_int
103acpi_timer_read()
104{
105 return (bus_space_read_4(acpi_timer_bst, acpi_timer_bsh, 0));
106}
107
108/*
109 * Locate the ACPI timer using the FADT, set up and allocate the I/O resources
110 * we will be using.
111 */
112static void
113acpi_timer_identify(driver_t *driver, device_t parent)
114{
115 device_t dev;
116 u_long rlen, rstart;
117 int rid, rtype;
118
119 ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
120
121 if (acpi_disabled("timer") || (acpi_quirks & ACPI_Q_TIMER) ||
122 AcpiGbl_FADT == NULL || acpi_timer_dev)
123 return_VOID;
124
125 if ((dev = BUS_ADD_CHILD(parent, 0, "acpi_timer", 0)) == NULL) {
126 device_printf(parent, "could not add acpi_timer0\n");
127 return_VOID;
128 }
129 acpi_timer_dev = dev;
130
131 rid = 0;
132 rtype = AcpiGbl_FADT->XPmTmrBlk.AddressSpaceId ?
133 SYS_RES_IOPORT : SYS_RES_MEMORY;
134 rlen = AcpiGbl_FADT->PmTmLen;
135 rstart = AcpiGbl_FADT->XPmTmrBlk.Address;
136 if (bus_set_resource(dev, rtype, rid, rstart, rlen))
137 device_printf(dev, "couldn't set resource (%s 0x%lx+0x%lx)\n",
138 (rtype == SYS_RES_IOPORT) ? "port" : "mem", rstart, rlen);
139 return_VOID;
140}
141
142static int
143acpi_timer_probe(device_t dev)
144{
145 char desc[40];
146 int i, j, rid, rtype;
147
148 ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
149
150 if (dev != acpi_timer_dev)
151 return (ENXIO);
152
153 rid = 0;
154 rtype = AcpiGbl_FADT->XPmTmrBlk.AddressSpaceId ?
155 SYS_RES_IOPORT : SYS_RES_MEMORY;
156 acpi_timer_reg = bus_alloc_resource_any(dev, rtype, &rid, RF_ACTIVE);
157 if (acpi_timer_reg == NULL) {
158 device_printf(dev, "couldn't allocate resource (%s 0x%lx)\n",
159 (rtype == SYS_RES_IOPORT) ? "port" : "mem",
160 (u_long)AcpiGbl_FADT->XPmTmrBlk.Address);
161 return (ENXIO);
162 }
163 acpi_timer_bsh = rman_get_bushandle(acpi_timer_reg);
164 acpi_timer_bst = rman_get_bustag(acpi_timer_reg);
165 if (AcpiGbl_FADT->TmrValExt != 0)
166 acpi_timer_timecounter.tc_counter_mask = 0xffffffff;
167 else
168 acpi_timer_timecounter.tc_counter_mask = 0x00ffffff;
169 acpi_timer_timecounter.tc_frequency = acpi_timer_frequency;
170 if (testenv("debug.acpi.timer_test"))
171 acpi_timer_boot_test();
172
173 /*
174 * If all tests of the counter succeed, use the ACPI-fast method. If
175 * at least one failed, default to using the safe routine, which reads
176 * the timer multiple times to get a consistent value before returning.
177 */
178 j = 0;
179 if (bootverbose)
180 printf("ACPI timer:");
181 for (i = 0; i < 10; i++)
182 j += acpi_timer_test();
183 if (bootverbose)
184 printf(" -> %d\n", j);
185 if (j == 10) {
186 acpi_timer_timecounter.tc_name = "ACPI-fast";
187 acpi_timer_timecounter.tc_get_timecount = acpi_timer_get_timecount;
188 } else {
189 acpi_timer_timecounter.tc_name = "ACPI-safe";
190 acpi_timer_timecounter.tc_get_timecount = acpi_timer_get_timecount_safe;
191 }
192 tc_init(&acpi_timer_timecounter);
193
194 sprintf(desc, "%d-bit timer at 3.579545MHz",
195 AcpiGbl_FADT->TmrValExt ? 32 : 24);
196 device_set_desc_copy(dev, desc);
197
198 /* Release the resource, we'll allocate it again during attach. */
199 bus_release_resource(dev, rtype, rid, acpi_timer_reg);
200 return (0);
201}
202
203static int
204acpi_timer_attach(device_t dev)
205{
206 int rid, rtype;
207
208 ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
209
210 rid = 0;
211 rtype = AcpiGbl_FADT->XPmTmrBlk.AddressSpaceId ?
212 SYS_RES_IOPORT : SYS_RES_MEMORY;
213 acpi_timer_reg = bus_alloc_resource_any(dev, rtype, &rid, RF_ACTIVE);
214 if (acpi_timer_reg == NULL)
215 return (ENXIO);
216 acpi_timer_bsh = rman_get_bushandle(acpi_timer_reg);
217 acpi_timer_bst = rman_get_bustag(acpi_timer_reg);
218 return (0);
219}
220
221/*
222 * Fetch current time value from reliable hardware.
223 */
224static u_int
225acpi_timer_get_timecount(struct timecounter *tc)
226{
227 return (acpi_timer_read());
228}
229
230/*
231 * Fetch current time value from hardware that may not correctly
232 * latch the counter. We need to read until we have three monotonic
233 * samples and then use the middle one, otherwise we are not protected
234 * against the fact that the bits can be wrong in two directions. If
235 * we only cared about monosity, two reads would be enough.
236 */
237static u_int
238acpi_timer_get_timecount_safe(struct timecounter *tc)
239{
240 u_int u1, u2, u3;
241
242 u2 = acpi_timer_read();
243 u3 = acpi_timer_read();
244 do {
245 u1 = u2;
246 u2 = u3;
247 u3 = acpi_timer_read();
248 } while (u1 > u2 || u2 > u3);
249
250 return (u2);
251}
252
253/*
254 * Timecounter freqency adjustment interface.
255 */
256static int
257acpi_timer_sysctl_freq(SYSCTL_HANDLER_ARGS)
258{
259 int error;
260 u_int freq;
261
262 if (acpi_timer_timecounter.tc_frequency == 0)
263 return (EOPNOTSUPP);
264 freq = acpi_timer_frequency;
265 error = sysctl_handle_int(oidp, &freq, sizeof(freq), req);
266 if (error == 0 && req->newptr != NULL) {
267 acpi_timer_frequency = freq;
268 acpi_timer_timecounter.tc_frequency = acpi_timer_frequency;
269 }
270
271 return (error);
272}
273
274SYSCTL_PROC(_machdep, OID_AUTO, acpi_timer_freq, CTLTYPE_INT | CTLFLAG_RW,
275 0, sizeof(u_int), acpi_timer_sysctl_freq, "I", "");
276
277/*
278 * Some ACPI timers are known or believed to suffer from implementation
279 * problems which can lead to erroneous values being read. This function
280 * tests for consistent results from the timer and returns 1 if it believes
281 * the timer is consistent, otherwise it returns 0.
282 *
283 * It appears the cause is that the counter is not latched to the PCI bus
284 * clock when read:
285 *
286 * ] 20. ACPI Timer Errata
287 * ]
288 * ] Problem: The power management timer may return improper result when
289 * ] read. Although the timer value settles properly after incrementing,
290 * ] while incrementing there is a 3nS window every 69.8nS where the
291 * ] timer value is indeterminate (a 4.2% chance that the data will be
292 * ] incorrect when read). As a result, the ACPI free running count up
293 * ] timer specification is violated due to erroneous reads. Implication:
294 * ] System hangs due to the "inaccuracy" of the timer when used by
295 * ] software for time critical events and delays.
296 * ]
297 * ] Workaround: Read the register twice and compare.
298 * ] Status: This will not be fixed in the PIIX4 or PIIX4E, it is fixed
299 * ] in the PIIX4M.
300 */
301#define N 2000
302static int
303acpi_timer_test()
304{
305 uint32_t last, this;
306 int min, max, n, delta;
307 register_t s;
308
309 min = 10000000;
310 max = 0;
311
312 /* Test the timer with interrupts disabled to get accurate results. */
313 s = intr_disable();
314 last = acpi_timer_read();
315 for (n = 0; n < N; n++) {
316 this = acpi_timer_read();
317 delta = acpi_TimerDelta(this, last);
318 if (delta > max)
319 max = delta;
320 else if (delta < min)
321 min = delta;
322 last = this;
323 }
324 intr_restore(s);
325
326 if (max - min > 2)
327 n = 0;
328 else if (min < 0 || max == 0)
329 n = 0;
330 else
331 n = 1;
332 if (bootverbose)
333 printf(" %d/%d", n, max-min);
334
335 return (n);
336}
337#undef N
338
339/*
340 * Test harness for verifying ACPI timer behaviour.
341 * Boot with debug.acpi.timer_test set to invoke this.
342 */
343static void
344acpi_timer_boot_test(void)
345{
346 uint32_t u1, u2, u3;
347
348 u1 = acpi_timer_read();
349 u2 = acpi_timer_read();
350 u3 = acpi_timer_read();
351
352 device_printf(acpi_timer_dev, "timer test in progress, reboot to quit.\n");
353 for (;;) {
354 /*
355 * The failure case is where u3 > u1, but u2 does not fall between
356 * the two, ie. it contains garbage.
357 */
358 if (u3 > u1) {
359 if (u2 < u1 || u2 > u3)
360 device_printf(acpi_timer_dev,
361 "timer is not monotonic: 0x%08x,0x%08x,0x%08x\n",
362 u1, u2, u3);
363 }
364 u1 = u2;
365 u2 = u3;
366 u3 = acpi_timer_read();
367 }
368}
| 44#include <dev/acpica/acpivar.h>
45#include <dev/pci/pcivar.h>
46
47/*
48 * A timecounter based on the free-running ACPI timer.
49 *
50 * Based on the i386-only mp_clock.c by <phk@FreeBSD.ORG>.
51 */
52
53/* Hooks for the ACPI CA debugging infrastructure */
54#define _COMPONENT ACPI_TIMER
55ACPI_MODULE_NAME("TIMER")
56
57static device_t acpi_timer_dev;
58static struct resource *acpi_timer_reg;
59static bus_space_handle_t acpi_timer_bsh;
60static bus_space_tag_t acpi_timer_bst;
61
62static u_int acpi_timer_frequency = 14318182 / 4;
63
64static void acpi_timer_identify(driver_t *driver, device_t parent);
65static int acpi_timer_probe(device_t dev);
66static int acpi_timer_attach(device_t dev);
67static u_int acpi_timer_get_timecount(struct timecounter *tc);
68static u_int acpi_timer_get_timecount_safe(struct timecounter *tc);
69static int acpi_timer_sysctl_freq(SYSCTL_HANDLER_ARGS);
70static void acpi_timer_boot_test(void);
71
72static u_int acpi_timer_read(void);
73static int acpi_timer_test(void);
74
75static device_method_t acpi_timer_methods[] = {
76 DEVMETHOD(device_identify, acpi_timer_identify),
77 DEVMETHOD(device_probe, acpi_timer_probe),
78 DEVMETHOD(device_attach, acpi_timer_attach),
79
80 {0, 0}
81};
82
83static driver_t acpi_timer_driver = {
84 "acpi_timer",
85 acpi_timer_methods,
86 0,
87};
88
89static devclass_t acpi_timer_devclass;
90DRIVER_MODULE(acpi_timer, acpi, acpi_timer_driver, acpi_timer_devclass, 0, 0);
91MODULE_DEPEND(acpi_timer, acpi, 1, 1, 1);
92
93static struct timecounter acpi_timer_timecounter = {
94 acpi_timer_get_timecount_safe, /* get_timecount function */
95 0, /* no poll_pps */
96 0, /* no default counter_mask */
97 0, /* no default frequency */
98 "ACPI", /* name */
99 1000 /* quality */
100};
101
102static u_int
103acpi_timer_read()
104{
105 return (bus_space_read_4(acpi_timer_bst, acpi_timer_bsh, 0));
106}
107
108/*
109 * Locate the ACPI timer using the FADT, set up and allocate the I/O resources
110 * we will be using.
111 */
112static void
113acpi_timer_identify(driver_t *driver, device_t parent)
114{
115 device_t dev;
116 u_long rlen, rstart;
117 int rid, rtype;
118
119 ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
120
121 if (acpi_disabled("timer") || (acpi_quirks & ACPI_Q_TIMER) ||
122 AcpiGbl_FADT == NULL || acpi_timer_dev)
123 return_VOID;
124
125 if ((dev = BUS_ADD_CHILD(parent, 0, "acpi_timer", 0)) == NULL) {
126 device_printf(parent, "could not add acpi_timer0\n");
127 return_VOID;
128 }
129 acpi_timer_dev = dev;
130
131 rid = 0;
132 rtype = AcpiGbl_FADT->XPmTmrBlk.AddressSpaceId ?
133 SYS_RES_IOPORT : SYS_RES_MEMORY;
134 rlen = AcpiGbl_FADT->PmTmLen;
135 rstart = AcpiGbl_FADT->XPmTmrBlk.Address;
136 if (bus_set_resource(dev, rtype, rid, rstart, rlen))
137 device_printf(dev, "couldn't set resource (%s 0x%lx+0x%lx)\n",
138 (rtype == SYS_RES_IOPORT) ? "port" : "mem", rstart, rlen);
139 return_VOID;
140}
141
142static int
143acpi_timer_probe(device_t dev)
144{
145 char desc[40];
146 int i, j, rid, rtype;
147
148 ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
149
150 if (dev != acpi_timer_dev)
151 return (ENXIO);
152
153 rid = 0;
154 rtype = AcpiGbl_FADT->XPmTmrBlk.AddressSpaceId ?
155 SYS_RES_IOPORT : SYS_RES_MEMORY;
156 acpi_timer_reg = bus_alloc_resource_any(dev, rtype, &rid, RF_ACTIVE);
157 if (acpi_timer_reg == NULL) {
158 device_printf(dev, "couldn't allocate resource (%s 0x%lx)\n",
159 (rtype == SYS_RES_IOPORT) ? "port" : "mem",
160 (u_long)AcpiGbl_FADT->XPmTmrBlk.Address);
161 return (ENXIO);
162 }
163 acpi_timer_bsh = rman_get_bushandle(acpi_timer_reg);
164 acpi_timer_bst = rman_get_bustag(acpi_timer_reg);
165 if (AcpiGbl_FADT->TmrValExt != 0)
166 acpi_timer_timecounter.tc_counter_mask = 0xffffffff;
167 else
168 acpi_timer_timecounter.tc_counter_mask = 0x00ffffff;
169 acpi_timer_timecounter.tc_frequency = acpi_timer_frequency;
170 if (testenv("debug.acpi.timer_test"))
171 acpi_timer_boot_test();
172
173 /*
174 * If all tests of the counter succeed, use the ACPI-fast method. If
175 * at least one failed, default to using the safe routine, which reads
176 * the timer multiple times to get a consistent value before returning.
177 */
178 j = 0;
179 if (bootverbose)
180 printf("ACPI timer:");
181 for (i = 0; i < 10; i++)
182 j += acpi_timer_test();
183 if (bootverbose)
184 printf(" -> %d\n", j);
185 if (j == 10) {
186 acpi_timer_timecounter.tc_name = "ACPI-fast";
187 acpi_timer_timecounter.tc_get_timecount = acpi_timer_get_timecount;
188 } else {
189 acpi_timer_timecounter.tc_name = "ACPI-safe";
190 acpi_timer_timecounter.tc_get_timecount = acpi_timer_get_timecount_safe;
191 }
192 tc_init(&acpi_timer_timecounter);
193
194 sprintf(desc, "%d-bit timer at 3.579545MHz",
195 AcpiGbl_FADT->TmrValExt ? 32 : 24);
196 device_set_desc_copy(dev, desc);
197
198 /* Release the resource, we'll allocate it again during attach. */
199 bus_release_resource(dev, rtype, rid, acpi_timer_reg);
200 return (0);
201}
202
203static int
204acpi_timer_attach(device_t dev)
205{
206 int rid, rtype;
207
208 ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
209
210 rid = 0;
211 rtype = AcpiGbl_FADT->XPmTmrBlk.AddressSpaceId ?
212 SYS_RES_IOPORT : SYS_RES_MEMORY;
213 acpi_timer_reg = bus_alloc_resource_any(dev, rtype, &rid, RF_ACTIVE);
214 if (acpi_timer_reg == NULL)
215 return (ENXIO);
216 acpi_timer_bsh = rman_get_bushandle(acpi_timer_reg);
217 acpi_timer_bst = rman_get_bustag(acpi_timer_reg);
218 return (0);
219}
220
221/*
222 * Fetch current time value from reliable hardware.
223 */
224static u_int
225acpi_timer_get_timecount(struct timecounter *tc)
226{
227 return (acpi_timer_read());
228}
229
230/*
231 * Fetch current time value from hardware that may not correctly
232 * latch the counter. We need to read until we have three monotonic
233 * samples and then use the middle one, otherwise we are not protected
234 * against the fact that the bits can be wrong in two directions. If
235 * we only cared about monosity, two reads would be enough.
236 */
237static u_int
238acpi_timer_get_timecount_safe(struct timecounter *tc)
239{
240 u_int u1, u2, u3;
241
242 u2 = acpi_timer_read();
243 u3 = acpi_timer_read();
244 do {
245 u1 = u2;
246 u2 = u3;
247 u3 = acpi_timer_read();
248 } while (u1 > u2 || u2 > u3);
249
250 return (u2);
251}
252
253/*
254 * Timecounter freqency adjustment interface.
255 */
256static int
257acpi_timer_sysctl_freq(SYSCTL_HANDLER_ARGS)
258{
259 int error;
260 u_int freq;
261
262 if (acpi_timer_timecounter.tc_frequency == 0)
263 return (EOPNOTSUPP);
264 freq = acpi_timer_frequency;
265 error = sysctl_handle_int(oidp, &freq, sizeof(freq), req);
266 if (error == 0 && req->newptr != NULL) {
267 acpi_timer_frequency = freq;
268 acpi_timer_timecounter.tc_frequency = acpi_timer_frequency;
269 }
270
271 return (error);
272}
273
274SYSCTL_PROC(_machdep, OID_AUTO, acpi_timer_freq, CTLTYPE_INT | CTLFLAG_RW,
275 0, sizeof(u_int), acpi_timer_sysctl_freq, "I", "");
276
277/*
278 * Some ACPI timers are known or believed to suffer from implementation
279 * problems which can lead to erroneous values being read. This function
280 * tests for consistent results from the timer and returns 1 if it believes
281 * the timer is consistent, otherwise it returns 0.
282 *
283 * It appears the cause is that the counter is not latched to the PCI bus
284 * clock when read:
285 *
286 * ] 20. ACPI Timer Errata
287 * ]
288 * ] Problem: The power management timer may return improper result when
289 * ] read. Although the timer value settles properly after incrementing,
290 * ] while incrementing there is a 3nS window every 69.8nS where the
291 * ] timer value is indeterminate (a 4.2% chance that the data will be
292 * ] incorrect when read). As a result, the ACPI free running count up
293 * ] timer specification is violated due to erroneous reads. Implication:
294 * ] System hangs due to the "inaccuracy" of the timer when used by
295 * ] software for time critical events and delays.
296 * ]
297 * ] Workaround: Read the register twice and compare.
298 * ] Status: This will not be fixed in the PIIX4 or PIIX4E, it is fixed
299 * ] in the PIIX4M.
300 */
301#define N 2000
302static int
303acpi_timer_test()
304{
305 uint32_t last, this;
306 int min, max, n, delta;
307 register_t s;
308
309 min = 10000000;
310 max = 0;
311
312 /* Test the timer with interrupts disabled to get accurate results. */
313 s = intr_disable();
314 last = acpi_timer_read();
315 for (n = 0; n < N; n++) {
316 this = acpi_timer_read();
317 delta = acpi_TimerDelta(this, last);
318 if (delta > max)
319 max = delta;
320 else if (delta < min)
321 min = delta;
322 last = this;
323 }
324 intr_restore(s);
325
326 if (max - min > 2)
327 n = 0;
328 else if (min < 0 || max == 0)
329 n = 0;
330 else
331 n = 1;
332 if (bootverbose)
333 printf(" %d/%d", n, max-min);
334
335 return (n);
336}
337#undef N
338
339/*
340 * Test harness for verifying ACPI timer behaviour.
341 * Boot with debug.acpi.timer_test set to invoke this.
342 */
343static void
344acpi_timer_boot_test(void)
345{
346 uint32_t u1, u2, u3;
347
348 u1 = acpi_timer_read();
349 u2 = acpi_timer_read();
350 u3 = acpi_timer_read();
351
352 device_printf(acpi_timer_dev, "timer test in progress, reboot to quit.\n");
353 for (;;) {
354 /*
355 * The failure case is where u3 > u1, but u2 does not fall between
356 * the two, ie. it contains garbage.
357 */
358 if (u3 > u1) {
359 if (u2 < u1 || u2 > u3)
360 device_printf(acpi_timer_dev,
361 "timer is not monotonic: 0x%08x,0x%08x,0x%08x\n",
362 u1, u2, u3);
363 }
364 u1 = u2;
365 u2 = u3;
366 u3 = acpi_timer_read();
367 }
368}
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