2 * linux/arch/i386/kernel/time_hpet.c
3 * This code largely copied from arch/x86_64/kernel/time.c
4 * See that file for credits.
6 * 2003-06-30 Venkatesh Pallipadi - Additional changes for HPET support
9 #include <linux/errno.h>
10 #include <linux/kernel.h>
11 #include <linux/param.h>
12 #include <linux/string.h>
13 #include <linux/init.h>
14 #include <linux/smp.h>
16 #include <asm/timer.h>
17 #include <asm/fixmap.h>
20 #include <linux/timex.h>
21 #include <linux/config.h>
25 unsigned long hpet_period; /* fsecs / HPET clock */
26 unsigned long hpet_tick; /* hpet clks count per tick */
27 unsigned long hpet_address; /* hpet memory map physical address */
29 static int use_hpet; /* can be used for runtime check of hpet */
30 static int boot_hpet_disable; /* boottime override for HPET timer */
31 static unsigned long hpet_virt_address; /* hpet kernel virtual address */
33 #define FSEC_TO_USEC (1000000000UL)
35 int hpet_readl(unsigned long a)
37 return readl(hpet_virt_address + a);
40 void hpet_writel(unsigned long d, unsigned long a)
42 writel(d, hpet_virt_address + a);
45 #ifdef CONFIG_X86_LOCAL_APIC
47 * HPET counters dont wrap around on every tick. They just change the
48 * comparator value and continue. Next tick can be caught by checking
49 * for a change in the comparator value. Used in apic.c.
51 void __init wait_hpet_tick(void)
53 unsigned int start_cmp_val, end_cmp_val;
55 start_cmp_val = hpet_readl(HPET_T0_CMP);
57 end_cmp_val = hpet_readl(HPET_T0_CMP);
58 } while (start_cmp_val == end_cmp_val);
63 * Check whether HPET was found by ACPI boot parse. If yes setup HPET
64 * counter 0 for kernel base timer.
66 int __init hpet_enable(void)
69 unsigned long tick_fsec_low, tick_fsec_high; /* tick in femto sec */
70 unsigned long hpet_tick_rem;
72 if (boot_hpet_disable)
78 hpet_virt_address = (unsigned long) ioremap_nocache(hpet_address,
81 * Read the period, compute tick and quotient.
83 id = hpet_readl(HPET_ID);
86 * We are checking for value '1' or more in number field.
87 * So, we are OK with HPET_EMULATE_RTC part too, where we need
88 * to have atleast 2 timers.
90 if (!(id & HPET_ID_NUMBER) ||
91 !(id & HPET_ID_LEGSUP))
94 hpet_period = hpet_readl(HPET_PERIOD);
95 if ((hpet_period < HPET_MIN_PERIOD) || (hpet_period > HPET_MAX_PERIOD))
100 * First changing tick into fsec
101 * Then 64 bit div to find number of hpet clk per tick
103 ASM_MUL64_REG(tick_fsec_low, tick_fsec_high,
104 KERNEL_TICK_USEC, FSEC_TO_USEC);
105 ASM_DIV64_REG(hpet_tick, hpet_tick_rem,
106 hpet_period, tick_fsec_low, tick_fsec_high);
108 if (hpet_tick_rem > (hpet_period >> 1))
109 hpet_tick++; /* rounding the result */
112 * Stop the timers and reset the main counter.
114 cfg = hpet_readl(HPET_CFG);
115 cfg &= ~HPET_CFG_ENABLE;
116 hpet_writel(cfg, HPET_CFG);
117 hpet_writel(0, HPET_COUNTER);
118 hpet_writel(0, HPET_COUNTER + 4);
121 * Set up timer 0, as periodic with first interrupt to happen at
122 * hpet_tick, and period also hpet_tick.
124 cfg = hpet_readl(HPET_T0_CFG);
125 cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC |
126 HPET_TN_SETVAL | HPET_TN_32BIT;
127 hpet_writel(cfg, HPET_T0_CFG);
128 hpet_writel(hpet_tick, HPET_T0_CMP);
133 cfg = hpet_readl(HPET_CFG);
134 cfg |= HPET_CFG_ENABLE | HPET_CFG_LEGACY;
135 hpet_writel(cfg, HPET_CFG);
138 #ifdef CONFIG_X86_LOCAL_APIC
139 wait_timer_tick = wait_hpet_tick;
144 int is_hpet_enabled(void)
149 int is_hpet_capable(void)
151 if (!boot_hpet_disable && hpet_address)
156 static int __init hpet_setup(char* str)
159 if (!strncmp("disable", str, 7))
160 boot_hpet_disable = 1;
165 __setup("hpet=", hpet_setup);
167 #ifdef CONFIG_HPET_EMULATE_RTC
168 /* HPET in LegacyReplacement Mode eats up RTC interrupt line. When, HPET
169 * is enabled, we support RTC interrupt functionality in software.
170 * RTC has 3 kinds of interrupts:
171 * 1) Update Interrupt - generate an interrupt, every sec, when RTC clock
173 * 2) Alarm Interrupt - generate an interrupt at a specific time of day
174 * 3) Periodic Interrupt - generate periodic interrupt, with frequencies
175 * 2Hz-8192Hz (2Hz-64Hz for non-root user) (all freqs in powers of 2)
176 * (1) and (2) above are implemented using polling at a frequency of
177 * 64 Hz. The exact frequency is a tradeoff between accuracy and interrupt
178 * overhead. (DEFAULT_RTC_INT_FREQ)
179 * For (3), we use interrupts at 64Hz or user specified periodic
180 * frequency, whichever is higher.
182 #include <linux/mc146818rtc.h>
183 #include <linux/rtc.h>
185 extern irqreturn_t rtc_interrupt(int irq, void *dev_id, struct pt_regs *regs);
187 #define DEFAULT_RTC_INT_FREQ 64
188 #define RTC_NUM_INTS 1
190 static unsigned long UIE_on;
191 static unsigned long prev_update_sec;
193 static unsigned long AIE_on;
194 static struct rtc_time alarm_time;
196 static unsigned long PIE_on;
197 static unsigned long PIE_freq = DEFAULT_RTC_INT_FREQ;
198 static unsigned long PIE_count;
200 static unsigned long hpet_rtc_int_freq; /* RTC interrupt frequency */
203 * Timer 1 for RTC, we do not use periodic interrupt feature,
204 * even if HPET supports periodic interrupts on Timer 1.
205 * The reason being, to set up a periodic interrupt in HPET, we need to
206 * stop the main counter. And if we do that everytime someone diables/enables
207 * RTC, we will have adverse effect on main kernel timer running on Timer 0.
208 * So, for the time being, simulate the periodic interrupt in software.
210 * hpet_rtc_timer_init() is called for the first time and during subsequent
211 * interuppts reinit happens through hpet_rtc_timer_reinit().
213 int hpet_rtc_timer_init(void)
215 unsigned int cfg, cnt;
218 if (!is_hpet_enabled())
221 * Set the counter 1 and enable the interrupts.
223 if (PIE_on && (PIE_freq > DEFAULT_RTC_INT_FREQ))
224 hpet_rtc_int_freq = PIE_freq;
226 hpet_rtc_int_freq = DEFAULT_RTC_INT_FREQ;
228 local_irq_save(flags);
229 cnt = hpet_readl(HPET_COUNTER);
230 cnt += ((hpet_tick*HZ)/hpet_rtc_int_freq);
231 hpet_writel(cnt, HPET_T1_CMP);
232 local_irq_restore(flags);
234 cfg = hpet_readl(HPET_T1_CFG);
235 cfg |= HPET_TN_ENABLE | HPET_TN_SETVAL | HPET_TN_32BIT;
236 hpet_writel(cfg, HPET_T1_CFG);
241 static void hpet_rtc_timer_reinit(void)
243 unsigned int cfg, cnt;
245 if (!(PIE_on | AIE_on | UIE_on))
248 if (PIE_on && (PIE_freq > DEFAULT_RTC_INT_FREQ))
249 hpet_rtc_int_freq = PIE_freq;
251 hpet_rtc_int_freq = DEFAULT_RTC_INT_FREQ;
253 /* It is more accurate to use the comparator value than current count.*/
254 cnt = hpet_readl(HPET_T1_CMP);
255 cnt += hpet_tick*HZ/hpet_rtc_int_freq;
256 hpet_writel(cnt, HPET_T1_CMP);
258 cfg = hpet_readl(HPET_T1_CFG);
259 cfg |= HPET_TN_ENABLE | HPET_TN_SETVAL | HPET_TN_32BIT;
260 hpet_writel(cfg, HPET_T1_CFG);
266 * The functions below are called from rtc driver.
267 * Return 0 if HPET is not being used.
268 * Otherwise do the necessary changes and return 1.
270 int hpet_mask_rtc_irq_bit(unsigned long bit_mask)
272 if (!is_hpet_enabled())
275 if (bit_mask & RTC_UIE)
277 if (bit_mask & RTC_PIE)
279 if (bit_mask & RTC_AIE)
285 int hpet_set_rtc_irq_bit(unsigned long bit_mask)
287 int timer_init_reqd = 0;
289 if (!is_hpet_enabled())
292 if (!(PIE_on | AIE_on | UIE_on))
295 if (bit_mask & RTC_UIE) {
298 if (bit_mask & RTC_PIE) {
302 if (bit_mask & RTC_AIE) {
307 hpet_rtc_timer_init();
312 int hpet_set_alarm_time(unsigned char hrs, unsigned char min, unsigned char sec)
314 if (!is_hpet_enabled())
317 alarm_time.tm_hour = hrs;
318 alarm_time.tm_min = min;
319 alarm_time.tm_sec = sec;
324 int hpet_set_periodic_freq(unsigned long freq)
326 if (!is_hpet_enabled())
335 int hpet_rtc_dropped_irq(void)
337 if (!is_hpet_enabled())
343 irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id, struct pt_regs *regs)
345 struct rtc_time curr_time;
346 unsigned long rtc_int_flag = 0;
347 int call_rtc_interrupt = 0;
349 hpet_rtc_timer_reinit();
351 if (UIE_on | AIE_on) {
352 rtc_get_rtc_time(&curr_time);
355 if (curr_time.tm_sec != prev_update_sec) {
356 /* Set update int info, call real rtc int routine */
357 call_rtc_interrupt = 1;
358 rtc_int_flag = RTC_UF;
359 prev_update_sec = curr_time.tm_sec;
364 if (PIE_count >= hpet_rtc_int_freq/PIE_freq) {
365 /* Set periodic int info, call real rtc int routine */
366 call_rtc_interrupt = 1;
367 rtc_int_flag |= RTC_PF;
372 if ((curr_time.tm_sec == alarm_time.tm_sec) &&
373 (curr_time.tm_min == alarm_time.tm_min) &&
374 (curr_time.tm_hour == alarm_time.tm_hour)) {
375 /* Set alarm int info, call real rtc int routine */
376 call_rtc_interrupt = 1;
377 rtc_int_flag |= RTC_AF;
380 if (call_rtc_interrupt) {
381 rtc_int_flag |= (RTC_IRQF | (RTC_NUM_INTS << 8));
382 rtc_interrupt(rtc_int_flag, dev_id, regs);