1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * 6522 Versatile Interface Adapter (VIA) |
4 | * |
5 | * There are two of these on the Mac II. Some IRQs are vectored |
6 | * via them as are assorted bits and bobs - eg RTC, ADB. |
7 | * |
8 | * CSA: Motorola seems to have removed documentation on the 6522 from |
9 | * their web site; try |
10 | * http://nerini.drf.com/vectrex/other/text/chips/6522/ |
11 | * http://www.zymurgy.net/classic/vic20/vicdet1.htm |
12 | * and |
13 | * http://193.23.168.87/mikro_laborversuche/via_iobaustein/via6522_1.html |
14 | * for info. A full-text web search on 6522 AND VIA will probably also |
15 | * net some usefulness. <cananian@alumni.princeton.edu> 20apr1999 |
16 | * |
17 | * Additional data is here (the SY6522 was used in the Mac II etc): |
18 | * http://www.6502.org/documents/datasheets/synertek/synertek_sy6522.pdf |
19 | * http://www.6502.org/documents/datasheets/synertek/synertek_sy6522_programming_reference.pdf |
20 | * |
21 | * PRAM/RTC access algorithms are from the NetBSD RTC toolkit version 1.08b |
22 | * by Erik Vogan and adapted to Linux by Joshua M. Thompson (funaho@jurai.org) |
23 | * |
24 | */ |
25 | |
26 | #include <linux/clocksource.h> |
27 | #include <linux/types.h> |
28 | #include <linux/kernel.h> |
29 | #include <linux/mm.h> |
30 | #include <linux/delay.h> |
31 | #include <linux/init.h> |
32 | #include <linux/module.h> |
33 | #include <linux/irq.h> |
34 | |
35 | #include <asm/macintosh.h> |
36 | #include <asm/macints.h> |
37 | #include <asm/mac_via.h> |
38 | #include <asm/mac_psc.h> |
39 | #include <asm/mac_oss.h> |
40 | |
41 | #include "mac.h" |
42 | |
43 | volatile __u8 *via1, *via2; |
44 | int rbv_present; |
45 | int via_alt_mapping; |
46 | EXPORT_SYMBOL(via_alt_mapping); |
47 | static __u8 rbv_clear; |
48 | |
49 | /* |
50 | * Globals for accessing the VIA chip registers without having to |
51 | * check if we're hitting a real VIA or an RBV. Normally you could |
52 | * just hit the combined register (ie, vIER|rIER) but that seems to |
53 | * break on AV Macs...probably because they actually decode more than |
54 | * eight address bits. Why can't Apple engineers at least be |
55 | * _consistently_ lazy? - 1999-05-21 (jmt) |
56 | */ |
57 | |
58 | static int gIER,gIFR,gBufA,gBufB; |
59 | |
60 | /* |
61 | * On Macs with a genuine VIA chip there is no way to mask an individual slot |
62 | * interrupt. This limitation also seems to apply to VIA clone logic cores in |
63 | * Quadra-like ASICs. (RBV and OSS machines don't have this limitation.) |
64 | * |
65 | * We used to fake it by configuring the relevant VIA pin as an output |
66 | * (to mask the interrupt) or input (to unmask). That scheme did not work on |
67 | * (at least) the Quadra 700. A NuBus card's /NMRQ signal is an open-collector |
68 | * circuit (see Designing Cards and Drivers for Macintosh II and Macintosh SE, |
69 | * p. 10-11 etc) but VIA outputs are not (see datasheet). |
70 | * |
71 | * Driving these outputs high must cause the VIA to source current and the |
72 | * card to sink current when it asserts /NMRQ. Current will flow but the pin |
73 | * voltage is uncertain and so the /NMRQ condition may still cause a transition |
74 | * at the VIA2 CA1 input (which explains the lost interrupts). A side effect |
75 | * is that a disabled slot IRQ can never be tested as pending or not. |
76 | * |
77 | * Driving these outputs low doesn't work either. All the slot /NMRQ lines are |
78 | * (active low) OR'd together to generate the CA1 (aka "SLOTS") interrupt (see |
79 | * The Guide To Macintosh Family Hardware, 2nd edition p. 167). If we drive a |
80 | * disabled /NMRQ line low, the falling edge immediately triggers a CA1 |
81 | * interrupt and all slot interrupts after that will generate no transition |
82 | * and therefore no interrupt, even after being re-enabled. |
83 | * |
84 | * So we make the VIA port A I/O lines inputs and use nubus_disabled to keep |
85 | * track of their states. When any slot IRQ becomes disabled we mask the CA1 |
86 | * umbrella interrupt. Only when all slot IRQs become enabled do we unmask |
87 | * the CA1 interrupt. It must remain enabled even when cards have no interrupt |
88 | * handler registered. Drivers must therefore disable a slot interrupt at the |
89 | * device before they call free_irq (like shared and autovector interrupts). |
90 | * |
91 | * There is also a related problem when MacOS is used to boot Linux. A network |
92 | * card brought up by a MacOS driver may raise an interrupt while Linux boots. |
93 | * This can be fatal since it can't be handled until the right driver loads |
94 | * (if such a driver exists at all). Apparently related to this hardware |
95 | * limitation, "Designing Cards and Drivers", p. 9-8, says that a slot |
96 | * interrupt with no driver would crash MacOS (the book was written before |
97 | * the appearance of Macs with RBV or OSS). |
98 | */ |
99 | |
100 | static u8 nubus_disabled; |
101 | |
102 | void via_debug_dump(void); |
103 | static void via_nubus_init(void); |
104 | |
105 | /* |
106 | * Initialize the VIAs |
107 | * |
108 | * First we figure out where they actually _are_ as well as what type of |
109 | * VIA we have for VIA2 (it could be a real VIA or an RBV or even an OSS.) |
110 | * Then we pretty much clear them out and disable all IRQ sources. |
111 | */ |
112 | |
113 | void __init via_init(void) |
114 | { |
115 | via1 = (void *)VIA1_BASE; |
116 | pr_debug("VIA1 detected at %p\n" , via1); |
117 | |
118 | if (oss_present) { |
119 | via2 = NULL; |
120 | rbv_present = 0; |
121 | } else { |
122 | switch (macintosh_config->via_type) { |
123 | |
124 | /* IIci, IIsi, IIvx, IIvi (P6xx), LC series */ |
125 | |
126 | case MAC_VIA_IICI: |
127 | via2 = (void *)RBV_BASE; |
128 | pr_debug("VIA2 (RBV) detected at %p\n" , via2); |
129 | rbv_present = 1; |
130 | if (macintosh_config->ident == MAC_MODEL_LCIII) { |
131 | rbv_clear = 0x00; |
132 | } else { |
133 | /* on most RBVs (& unlike the VIAs), you */ |
134 | /* need to set bit 7 when you write to IFR */ |
135 | /* in order for your clear to occur. */ |
136 | rbv_clear = 0x80; |
137 | } |
138 | gIER = rIER; |
139 | gIFR = rIFR; |
140 | gBufA = rSIFR; |
141 | gBufB = rBufB; |
142 | break; |
143 | |
144 | /* Quadra and early MacIIs agree on the VIA locations */ |
145 | |
146 | case MAC_VIA_QUADRA: |
147 | case MAC_VIA_II: |
148 | via2 = (void *) VIA2_BASE; |
149 | pr_debug("VIA2 detected at %p\n" , via2); |
150 | rbv_present = 0; |
151 | rbv_clear = 0x00; |
152 | gIER = vIER; |
153 | gIFR = vIFR; |
154 | gBufA = vBufA; |
155 | gBufB = vBufB; |
156 | break; |
157 | |
158 | default: |
159 | panic(fmt: "UNKNOWN VIA TYPE" ); |
160 | } |
161 | } |
162 | |
163 | #ifdef DEBUG_VIA |
164 | via_debug_dump(); |
165 | #endif |
166 | |
167 | /* |
168 | * Shut down all IRQ sources, reset the timers, and |
169 | * kill the timer latch on VIA1. |
170 | */ |
171 | |
172 | via1[vIER] = 0x7F; |
173 | via1[vIFR] = 0x7F; |
174 | via1[vT1CL] = 0; |
175 | via1[vT1CH] = 0; |
176 | via1[vT2CL] = 0; |
177 | via1[vT2CH] = 0; |
178 | via1[vACR] &= ~0xC0; /* setup T1 timer with no PB7 output */ |
179 | via1[vACR] &= ~0x03; /* disable port A & B latches */ |
180 | |
181 | /* |
182 | * SE/30: disable video IRQ |
183 | */ |
184 | |
185 | if (macintosh_config->ident == MAC_MODEL_SE30) { |
186 | via1[vDirB] |= 0x40; |
187 | via1[vBufB] |= 0x40; |
188 | } |
189 | |
190 | switch (macintosh_config->adb_type) { |
191 | case MAC_ADB_IOP: |
192 | case MAC_ADB_II: |
193 | case MAC_ADB_PB1: |
194 | /* |
195 | * Set the RTC bits to a known state: all lines to outputs and |
196 | * RTC disabled (yes that's 0 to enable and 1 to disable). |
197 | */ |
198 | via1[vDirB] |= VIA1B_vRTCEnb | VIA1B_vRTCClk | VIA1B_vRTCData; |
199 | via1[vBufB] |= VIA1B_vRTCEnb | VIA1B_vRTCClk; |
200 | break; |
201 | } |
202 | |
203 | /* Everything below this point is VIA2/RBV only... */ |
204 | |
205 | if (oss_present) |
206 | return; |
207 | |
208 | if ((macintosh_config->via_type == MAC_VIA_QUADRA) && |
209 | (macintosh_config->adb_type != MAC_ADB_PB1) && |
210 | (macintosh_config->adb_type != MAC_ADB_PB2) && |
211 | (macintosh_config->ident != MAC_MODEL_C660) && |
212 | (macintosh_config->ident != MAC_MODEL_Q840)) { |
213 | via_alt_mapping = 1; |
214 | via1[vDirB] |= 0x40; |
215 | via1[vBufB] &= ~0x40; |
216 | } else { |
217 | via_alt_mapping = 0; |
218 | } |
219 | |
220 | /* |
221 | * Now initialize VIA2. For RBV we just kill all interrupts; |
222 | * for a regular VIA we also reset the timers and stuff. |
223 | */ |
224 | |
225 | via2[gIER] = 0x7F; |
226 | via2[gIFR] = 0x7F | rbv_clear; |
227 | if (!rbv_present) { |
228 | via2[vT1CL] = 0; |
229 | via2[vT1CH] = 0; |
230 | via2[vT2CL] = 0; |
231 | via2[vT2CH] = 0; |
232 | via2[vACR] &= ~0xC0; /* setup T1 timer with no PB7 output */ |
233 | via2[vACR] &= ~0x03; /* disable port A & B latches */ |
234 | } |
235 | |
236 | via_nubus_init(); |
237 | |
238 | /* Everything below this point is VIA2 only... */ |
239 | |
240 | if (rbv_present) |
241 | return; |
242 | |
243 | /* |
244 | * Set vPCR for control line interrupts. |
245 | * |
246 | * CA1 (SLOTS IRQ), CB1 (ASC IRQ): negative edge trigger. |
247 | * |
248 | * Macs with ESP SCSI have a negative edge triggered SCSI interrupt. |
249 | * Testing reveals that PowerBooks do too. However, the SE/30 |
250 | * schematic diagram shows an active high NCR5380 IRQ line. |
251 | */ |
252 | |
253 | pr_debug("VIA2 vPCR is 0x%02X\n" , via2[vPCR]); |
254 | if (macintosh_config->via_type == MAC_VIA_II) { |
255 | /* CA2 (SCSI DRQ), CB2 (SCSI IRQ): indep. input, pos. edge */ |
256 | via2[vPCR] = 0x66; |
257 | } else { |
258 | /* CA2 (SCSI DRQ), CB2 (SCSI IRQ): indep. input, neg. edge */ |
259 | via2[vPCR] = 0x22; |
260 | } |
261 | } |
262 | |
263 | /* |
264 | * Debugging dump, used in various places to see what's going on. |
265 | */ |
266 | |
267 | void via_debug_dump(void) |
268 | { |
269 | printk(KERN_DEBUG "VIA1: DDRA = 0x%02X DDRB = 0x%02X ACR = 0x%02X\n" , |
270 | (uint) via1[vDirA], (uint) via1[vDirB], (uint) via1[vACR]); |
271 | printk(KERN_DEBUG " PCR = 0x%02X IFR = 0x%02X IER = 0x%02X\n" , |
272 | (uint) via1[vPCR], (uint) via1[vIFR], (uint) via1[vIER]); |
273 | if (!via2) |
274 | return; |
275 | if (rbv_present) { |
276 | printk(KERN_DEBUG "VIA2: IFR = 0x%02X IER = 0x%02X\n" , |
277 | (uint) via2[rIFR], (uint) via2[rIER]); |
278 | printk(KERN_DEBUG " SIFR = 0x%02X SIER = 0x%02X\n" , |
279 | (uint) via2[rSIFR], (uint) via2[rSIER]); |
280 | } else { |
281 | printk(KERN_DEBUG "VIA2: DDRA = 0x%02X DDRB = 0x%02X ACR = 0x%02X\n" , |
282 | (uint) via2[vDirA], (uint) via2[vDirB], |
283 | (uint) via2[vACR]); |
284 | printk(KERN_DEBUG " PCR = 0x%02X IFR = 0x%02X IER = 0x%02X\n" , |
285 | (uint) via2[vPCR], |
286 | (uint) via2[vIFR], (uint) via2[vIER]); |
287 | } |
288 | } |
289 | |
290 | /* |
291 | * Flush the L2 cache on Macs that have it by flipping |
292 | * the system into 24-bit mode for an instant. |
293 | */ |
294 | |
295 | void via_l2_flush(int writeback) |
296 | { |
297 | unsigned long flags; |
298 | |
299 | local_irq_save(flags); |
300 | via2[gBufB] &= ~VIA2B_vMode32; |
301 | via2[gBufB] |= VIA2B_vMode32; |
302 | local_irq_restore(flags); |
303 | } |
304 | |
305 | /* |
306 | * Initialize VIA2 for Nubus access |
307 | */ |
308 | |
309 | static void __init via_nubus_init(void) |
310 | { |
311 | /* unlock nubus transactions */ |
312 | |
313 | if ((macintosh_config->adb_type != MAC_ADB_PB1) && |
314 | (macintosh_config->adb_type != MAC_ADB_PB2)) { |
315 | /* set the line to be an output on non-RBV machines */ |
316 | if (!rbv_present) |
317 | via2[vDirB] |= 0x02; |
318 | |
319 | /* this seems to be an ADB bit on PMU machines */ |
320 | /* according to MkLinux. -- jmt */ |
321 | via2[gBufB] |= 0x02; |
322 | } |
323 | |
324 | /* |
325 | * Disable the slot interrupts. On some hardware that's not possible. |
326 | * On some hardware it's unclear what all of these I/O lines do. |
327 | */ |
328 | |
329 | switch (macintosh_config->via_type) { |
330 | case MAC_VIA_II: |
331 | case MAC_VIA_QUADRA: |
332 | pr_debug("VIA2 vDirA is 0x%02X\n" , via2[vDirA]); |
333 | break; |
334 | case MAC_VIA_IICI: |
335 | /* RBV. Disable all the slot interrupts. SIER works like IER. */ |
336 | via2[rSIER] = 0x7F; |
337 | break; |
338 | } |
339 | } |
340 | |
341 | void via_nubus_irq_startup(int irq) |
342 | { |
343 | int irq_idx = IRQ_IDX(irq); |
344 | |
345 | switch (macintosh_config->via_type) { |
346 | case MAC_VIA_II: |
347 | case MAC_VIA_QUADRA: |
348 | /* Make the port A line an input. Probably redundant. */ |
349 | if (macintosh_config->via_type == MAC_VIA_II) { |
350 | /* The top two bits are RAM size outputs. */ |
351 | via2[vDirA] &= 0xC0 | ~(1 << irq_idx); |
352 | } else { |
353 | /* Allow NuBus slots 9 through F. */ |
354 | via2[vDirA] &= 0x80 | ~(1 << irq_idx); |
355 | } |
356 | fallthrough; |
357 | case MAC_VIA_IICI: |
358 | via_irq_enable(irq); |
359 | break; |
360 | } |
361 | } |
362 | |
363 | void via_nubus_irq_shutdown(int irq) |
364 | { |
365 | switch (macintosh_config->via_type) { |
366 | case MAC_VIA_II: |
367 | case MAC_VIA_QUADRA: |
368 | /* Ensure that the umbrella CA1 interrupt remains enabled. */ |
369 | via_irq_enable(irq); |
370 | break; |
371 | case MAC_VIA_IICI: |
372 | via_irq_disable(irq); |
373 | break; |
374 | } |
375 | } |
376 | |
377 | /* |
378 | * The generic VIA interrupt routines (shamelessly stolen from Alan Cox's |
379 | * via6522.c :-), disable/pending masks added. |
380 | */ |
381 | |
382 | #define VIA_TIMER_1_INT BIT(6) |
383 | |
384 | void via1_irq(struct irq_desc *desc) |
385 | { |
386 | int irq_num; |
387 | unsigned char irq_bit, events; |
388 | |
389 | events = via1[vIFR] & via1[vIER] & 0x7F; |
390 | if (!events) |
391 | return; |
392 | |
393 | irq_num = IRQ_MAC_TIMER_1; |
394 | irq_bit = VIA_TIMER_1_INT; |
395 | if (events & irq_bit) { |
396 | unsigned long flags; |
397 | |
398 | local_irq_save(flags); |
399 | via1[vIFR] = irq_bit; |
400 | generic_handle_irq(irq: irq_num); |
401 | local_irq_restore(flags); |
402 | |
403 | events &= ~irq_bit; |
404 | if (!events) |
405 | return; |
406 | } |
407 | |
408 | irq_num = VIA1_SOURCE_BASE; |
409 | irq_bit = 1; |
410 | do { |
411 | if (events & irq_bit) { |
412 | via1[vIFR] = irq_bit; |
413 | generic_handle_irq(irq: irq_num); |
414 | } |
415 | ++irq_num; |
416 | irq_bit <<= 1; |
417 | } while (events >= irq_bit); |
418 | } |
419 | |
420 | static void via2_irq(struct irq_desc *desc) |
421 | { |
422 | int irq_num; |
423 | unsigned char irq_bit, events; |
424 | |
425 | events = via2[gIFR] & via2[gIER] & 0x7F; |
426 | if (!events) |
427 | return; |
428 | |
429 | irq_num = VIA2_SOURCE_BASE; |
430 | irq_bit = 1; |
431 | do { |
432 | if (events & irq_bit) { |
433 | via2[gIFR] = irq_bit | rbv_clear; |
434 | generic_handle_irq(irq: irq_num); |
435 | } |
436 | ++irq_num; |
437 | irq_bit <<= 1; |
438 | } while (events >= irq_bit); |
439 | } |
440 | |
441 | /* |
442 | * Dispatch Nubus interrupts. We are called as a secondary dispatch by the |
443 | * VIA2 dispatcher as a fast interrupt handler. |
444 | */ |
445 | |
446 | static void via_nubus_irq(struct irq_desc *desc) |
447 | { |
448 | int slot_irq; |
449 | unsigned char slot_bit, events; |
450 | |
451 | events = ~via2[gBufA] & 0x7F; |
452 | if (rbv_present) |
453 | events &= via2[rSIER]; |
454 | else |
455 | events &= ~via2[vDirA]; |
456 | if (!events) |
457 | return; |
458 | |
459 | do { |
460 | slot_irq = IRQ_NUBUS_F; |
461 | slot_bit = 0x40; |
462 | do { |
463 | if (events & slot_bit) { |
464 | events &= ~slot_bit; |
465 | generic_handle_irq(irq: slot_irq); |
466 | } |
467 | --slot_irq; |
468 | slot_bit >>= 1; |
469 | } while (events); |
470 | |
471 | /* clear the CA1 interrupt and make certain there's no more. */ |
472 | via2[gIFR] = 0x02 | rbv_clear; |
473 | events = ~via2[gBufA] & 0x7F; |
474 | if (rbv_present) |
475 | events &= via2[rSIER]; |
476 | else |
477 | events &= ~via2[vDirA]; |
478 | } while (events); |
479 | } |
480 | |
481 | /* |
482 | * Register the interrupt dispatchers for VIA or RBV machines only. |
483 | */ |
484 | |
485 | void __init via_register_interrupts(void) |
486 | { |
487 | if (via_alt_mapping) { |
488 | /* software interrupt */ |
489 | irq_set_chained_handler(IRQ_AUTO_1, via1_irq); |
490 | /* via1 interrupt */ |
491 | irq_set_chained_handler(IRQ_AUTO_6, via1_irq); |
492 | } else { |
493 | irq_set_chained_handler(IRQ_AUTO_1, via1_irq); |
494 | } |
495 | irq_set_chained_handler(IRQ_AUTO_2, via2_irq); |
496 | irq_set_chained_handler(IRQ_MAC_NUBUS, via_nubus_irq); |
497 | } |
498 | |
499 | void via_irq_enable(int irq) { |
500 | int irq_src = IRQ_SRC(irq); |
501 | int irq_idx = IRQ_IDX(irq); |
502 | |
503 | if (irq_src == 1) { |
504 | via1[vIER] = IER_SET_BIT(irq_idx); |
505 | } else if (irq_src == 2) { |
506 | if (irq != IRQ_MAC_NUBUS || nubus_disabled == 0) |
507 | via2[gIER] = IER_SET_BIT(irq_idx); |
508 | } else if (irq_src == 7) { |
509 | switch (macintosh_config->via_type) { |
510 | case MAC_VIA_II: |
511 | case MAC_VIA_QUADRA: |
512 | nubus_disabled &= ~(1 << irq_idx); |
513 | /* Enable the CA1 interrupt when no slot is disabled. */ |
514 | if (!nubus_disabled) |
515 | via2[gIER] = IER_SET_BIT(1); |
516 | break; |
517 | case MAC_VIA_IICI: |
518 | /* On RBV, enable the slot interrupt. |
519 | * SIER works like IER. |
520 | */ |
521 | via2[rSIER] = IER_SET_BIT(irq_idx); |
522 | break; |
523 | } |
524 | } |
525 | } |
526 | |
527 | void via_irq_disable(int irq) { |
528 | int irq_src = IRQ_SRC(irq); |
529 | int irq_idx = IRQ_IDX(irq); |
530 | |
531 | if (irq_src == 1) { |
532 | via1[vIER] = IER_CLR_BIT(irq_idx); |
533 | } else if (irq_src == 2) { |
534 | via2[gIER] = IER_CLR_BIT(irq_idx); |
535 | } else if (irq_src == 7) { |
536 | switch (macintosh_config->via_type) { |
537 | case MAC_VIA_II: |
538 | case MAC_VIA_QUADRA: |
539 | nubus_disabled |= 1 << irq_idx; |
540 | if (nubus_disabled) |
541 | via2[gIER] = IER_CLR_BIT(1); |
542 | break; |
543 | case MAC_VIA_IICI: |
544 | via2[rSIER] = IER_CLR_BIT(irq_idx); |
545 | break; |
546 | } |
547 | } |
548 | } |
549 | |
550 | void via1_set_head(int head) |
551 | { |
552 | if (head == 0) |
553 | via1[vBufA] &= ~VIA1A_vHeadSel; |
554 | else |
555 | via1[vBufA] |= VIA1A_vHeadSel; |
556 | } |
557 | EXPORT_SYMBOL(via1_set_head); |
558 | |
559 | int via2_scsi_drq_pending(void) |
560 | { |
561 | return via2[gIFR] & (1 << IRQ_IDX(IRQ_MAC_SCSIDRQ)); |
562 | } |
563 | EXPORT_SYMBOL(via2_scsi_drq_pending); |
564 | |
565 | /* timer and clock source */ |
566 | |
567 | #define VIA_CLOCK_FREQ 783360 /* VIA "phase 2" clock in Hz */ |
568 | #define VIA_TIMER_CYCLES (VIA_CLOCK_FREQ / HZ) /* clock cycles per jiffy */ |
569 | |
570 | #define VIA_TC (VIA_TIMER_CYCLES - 2) /* including 0 and -1 */ |
571 | #define VIA_TC_LOW (VIA_TC & 0xFF) |
572 | #define VIA_TC_HIGH (VIA_TC >> 8) |
573 | |
574 | static u64 mac_read_clk(struct clocksource *cs); |
575 | |
576 | static struct clocksource mac_clk = { |
577 | .name = "via1" , |
578 | .rating = 250, |
579 | .read = mac_read_clk, |
580 | .mask = CLOCKSOURCE_MASK(32), |
581 | .flags = CLOCK_SOURCE_IS_CONTINUOUS, |
582 | }; |
583 | |
584 | static u32 clk_total, clk_offset; |
585 | |
586 | static irqreturn_t via_timer_handler(int irq, void *dev_id) |
587 | { |
588 | clk_total += VIA_TIMER_CYCLES; |
589 | clk_offset = 0; |
590 | legacy_timer_tick(ticks: 1); |
591 | |
592 | return IRQ_HANDLED; |
593 | } |
594 | |
595 | void __init via_init_clock(void) |
596 | { |
597 | if (request_irq(IRQ_MAC_TIMER_1, via_timer_handler, IRQF_TIMER, "timer" , |
598 | NULL)) { |
599 | pr_err("Couldn't register %s interrupt\n" , "timer" ); |
600 | return; |
601 | } |
602 | |
603 | via1[vT1CL] = VIA_TC_LOW; |
604 | via1[vT1CH] = VIA_TC_HIGH; |
605 | via1[vACR] |= 0x40; |
606 | |
607 | clocksource_register_hz(cs: &mac_clk, VIA_CLOCK_FREQ); |
608 | } |
609 | |
610 | static u64 mac_read_clk(struct clocksource *cs) |
611 | { |
612 | unsigned long flags; |
613 | u8 count_high; |
614 | u16 count; |
615 | u32 ticks; |
616 | |
617 | /* |
618 | * Timer counter wrap-around is detected with the timer interrupt flag |
619 | * but reading the counter low byte (vT1CL) would reset the flag. |
620 | * Also, accessing both counter registers is essentially a data race. |
621 | * These problems are avoided by ignoring the low byte. Clock accuracy |
622 | * is 256 times worse (error can reach 0.327 ms) but CPU overhead is |
623 | * reduced by avoiding slow VIA register accesses. |
624 | */ |
625 | |
626 | local_irq_save(flags); |
627 | count_high = via1[vT1CH]; |
628 | if (count_high == 0xFF) |
629 | count_high = 0; |
630 | if (count_high > 0 && (via1[vIFR] & VIA_TIMER_1_INT)) |
631 | clk_offset = VIA_TIMER_CYCLES; |
632 | count = count_high << 8; |
633 | ticks = VIA_TIMER_CYCLES - count; |
634 | ticks += clk_offset + clk_total; |
635 | local_irq_restore(flags); |
636 | |
637 | return ticks; |
638 | } |
639 | |