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Linux/arch/cris/arch-v10/kernel/time.c

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  1 /*
  2  *  linux/arch/cris/arch-v10/kernel/time.c
  3  *
  4  *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
  5  *  Copyright (C) 1999-2002 Axis Communications AB
  6  *
  7  */
  8 
  9 #include <linux/timex.h>
 10 #include <linux/time.h>
 11 #include <linux/jiffies.h>
 12 #include <linux/interrupt.h>
 13 #include <linux/swap.h>
 14 #include <linux/sched.h>
 15 #include <linux/init.h>
 16 #include <linux/mm.h>
 17 #include <asm/types.h>
 18 #include <asm/signal.h>
 19 #include <asm/io.h>
 20 #include <asm/delay.h>
 21 #include <asm/irq_regs.h>
 22 
 23 /* define this if you need to use print_timestamp */
 24 /* it will make jiffies at 96 hz instead of 100 hz though */
 25 #undef USE_CASCADE_TIMERS
 26 
 27 unsigned long get_ns_in_jiffie(void)
 28 {
 29         unsigned char timer_count, t1;
 30         unsigned short presc_count;
 31         unsigned long ns;
 32         unsigned long flags;
 33 
 34         local_irq_save(flags);
 35         timer_count = *R_TIMER0_DATA;
 36         presc_count = *R_TIM_PRESC_STATUS;
 37         /* presc_count might be wrapped */
 38         t1 = *R_TIMER0_DATA;
 39 
 40         if (timer_count != t1){
 41                 /* it wrapped, read prescaler again...  */
 42                 presc_count = *R_TIM_PRESC_STATUS;
 43                 timer_count = t1;
 44         }
 45         local_irq_restore(flags);
 46         if (presc_count >= PRESCALE_VALUE/2 ){
 47                 presc_count =  PRESCALE_VALUE - presc_count + PRESCALE_VALUE/2;
 48         } else {
 49                 presc_count =  PRESCALE_VALUE - presc_count - PRESCALE_VALUE/2;
 50         }
 51 
 52         ns = ( (TIMER0_DIV - timer_count) * ((1000000000/HZ)/TIMER0_DIV )) +
 53              ( (presc_count) * (1000000000/PRESCALE_FREQ));
 54         return ns;
 55 }
 56 
 57 static u32 cris_v10_gettimeoffset(void)
 58 {
 59         u32 count;
 60 
 61         /* The timer interrupt comes from Etrax timer 0. In order to get
 62          * better precision, we check the current value. It might have
 63          * underflowed already though.
 64          */
 65         count = *R_TIMER0_DATA;
 66 
 67         /* Convert timer value to nsec */
 68         return (TIMER0_DIV - count) * (NSEC_PER_SEC/HZ)/TIMER0_DIV;
 69 }
 70 
 71 /* Excerpt from the Etrax100 HSDD about the built-in watchdog:
 72  *
 73  * 3.10.4 Watchdog timer
 74 
 75  * When the watchdog timer is started, it generates an NMI if the watchdog
 76  * isn't restarted or stopped within 0.1 s. If it still isn't restarted or
 77  * stopped after an additional 3.3 ms, the watchdog resets the chip.
 78  * The watchdog timer is stopped after reset. The watchdog timer is controlled
 79  * by the R_WATCHDOG register. The R_WATCHDOG register contains an enable bit
 80  * and a 3-bit key value. The effect of writing to the R_WATCHDOG register is
 81  * described in the table below:
 82  *
 83  *   Watchdog    Value written:
 84  *   state:      To enable:  To key:      Operation:
 85  *   --------    ----------  -------      ----------
 86  *   stopped         0         X          No effect.
 87  *   stopped         1       key_val      Start watchdog with key = key_val.
 88  *   started         0       ~key         Stop watchdog
 89  *   started         1       ~key         Restart watchdog with key = ~key.
 90  *   started         X       new_key_val  Change key to new_key_val.
 91  *
 92  * Note: '~' is the bitwise NOT operator.
 93  *
 94  */
 95 
 96 /* right now, starting the watchdog is the same as resetting it */
 97 #define start_watchdog reset_watchdog
 98 
 99 #ifdef CONFIG_ETRAX_WATCHDOG
100 static int watchdog_key = 0;  /* arbitrary number */
101 #endif
102 
103 /* number of pages to consider "out of memory". it is normal that the memory
104  * is used though, so put this really low.
105  */
106 
107 #define WATCHDOG_MIN_FREE_PAGES 8
108 
109 void reset_watchdog(void)
110 {
111 #if defined(CONFIG_ETRAX_WATCHDOG)
112         /* only keep watchdog happy as long as we have memory left! */
113         if(nr_free_pages() > WATCHDOG_MIN_FREE_PAGES) {
114                 /* reset the watchdog with the inverse of the old key */
115                 watchdog_key ^= 0x7; /* invert key, which is 3 bits */
116                 *R_WATCHDOG = IO_FIELD(R_WATCHDOG, key, watchdog_key) |
117                         IO_STATE(R_WATCHDOG, enable, start);
118         }
119 #endif
120 }
121 
122 /* stop the watchdog - we still need the correct key */
123 
124 void stop_watchdog(void)
125 {
126 #ifdef CONFIG_ETRAX_WATCHDOG
127         watchdog_key ^= 0x7; /* invert key, which is 3 bits */
128         *R_WATCHDOG = IO_FIELD(R_WATCHDOG, key, watchdog_key) |
129                 IO_STATE(R_WATCHDOG, enable, stop);
130 #endif
131 }
132 
133 
134 extern void cris_do_profile(struct pt_regs *regs);
135 
136 /*
137  * timer_interrupt() needs to keep up the real-time clock,
138  * as well as call the "xtime_update()" routine every clocktick
139  */
140 static inline irqreturn_t timer_interrupt(int irq, void *dev_id)
141 {
142         struct pt_regs *regs = get_irq_regs();
143         /* acknowledge the timer irq */
144 
145 #ifdef USE_CASCADE_TIMERS
146         *R_TIMER_CTRL =
147                 IO_FIELD( R_TIMER_CTRL, timerdiv1, 0) |
148                 IO_FIELD( R_TIMER_CTRL, timerdiv0, 0) |
149                 IO_STATE( R_TIMER_CTRL, i1, clr) |
150                 IO_STATE( R_TIMER_CTRL, tm1, run) |
151                 IO_STATE( R_TIMER_CTRL, clksel1, cascade0) |
152                 IO_STATE( R_TIMER_CTRL, i0, clr) |
153                 IO_STATE( R_TIMER_CTRL, tm0, run) |
154                 IO_STATE( R_TIMER_CTRL, clksel0, c6250kHz);
155 #else
156         *R_TIMER_CTRL = r_timer_ctrl_shadow | IO_STATE(R_TIMER_CTRL, i0, clr);
157 #endif
158 
159         /* reset watchdog otherwise it resets us! */
160         reset_watchdog();
161 
162         /* Update statistics. */
163         update_process_times(user_mode(regs));
164 
165         /* call the real timer interrupt handler */
166         xtime_update(1);
167 
168         cris_do_profile(regs); /* Save profiling information */
169         return IRQ_HANDLED;
170 }
171 
172 /* timer is IRQF_SHARED so drivers can add stuff to the timer irq chain */
173 
174 static struct irqaction irq2  = {
175         .handler = timer_interrupt,
176         .flags = IRQF_SHARED,
177         .name = "timer",
178 };
179 
180 void __init time_init(void)
181 {
182         arch_gettimeoffset = cris_v10_gettimeoffset;
183 
184         /* probe for the RTC and read it if it exists
185          * Before the RTC can be probed the loops_per_usec variable needs
186          * to be initialized to make usleep work. A better value for
187          * loops_per_usec is calculated by the kernel later once the
188          * clock has started.
189          */
190         loops_per_usec = 50;
191 
192         /* Setup the etrax timers
193          * Base frequency is 25000 hz, divider 250 -> 100 HZ
194          * In normal mode, we use timer0, so timer1 is free. In cascade
195          * mode (which we sometimes use for debugging) both timers are used.
196          * Remember that linux/timex.h contains #defines that rely on the
197          * timer settings below (hz and divide factor) !!!
198          */
199 
200 #ifdef USE_CASCADE_TIMERS
201         *R_TIMER_CTRL =
202                 IO_FIELD( R_TIMER_CTRL, timerdiv1, 0) |
203                 IO_FIELD( R_TIMER_CTRL, timerdiv0, 0) |
204                 IO_STATE( R_TIMER_CTRL, i1, nop) |
205                 IO_STATE( R_TIMER_CTRL, tm1, stop_ld) |
206                 IO_STATE( R_TIMER_CTRL, clksel1, cascade0) |
207                 IO_STATE( R_TIMER_CTRL, i0, nop) |
208                 IO_STATE( R_TIMER_CTRL, tm0, stop_ld) |
209                 IO_STATE( R_TIMER_CTRL, clksel0, c6250kHz);
210 
211         *R_TIMER_CTRL = r_timer_ctrl_shadow =
212                 IO_FIELD( R_TIMER_CTRL, timerdiv1, 0) |
213                 IO_FIELD( R_TIMER_CTRL, timerdiv0, 0) |
214                 IO_STATE( R_TIMER_CTRL, i1, nop) |
215                 IO_STATE( R_TIMER_CTRL, tm1, run) |
216                 IO_STATE( R_TIMER_CTRL, clksel1, cascade0) |
217                 IO_STATE( R_TIMER_CTRL, i0, nop) |
218                 IO_STATE( R_TIMER_CTRL, tm0, run) |
219                 IO_STATE( R_TIMER_CTRL, clksel0, c6250kHz);
220 #else
221         *R_TIMER_CTRL =
222                 IO_FIELD(R_TIMER_CTRL, timerdiv1, 192)      |
223                 IO_FIELD(R_TIMER_CTRL, timerdiv0, TIMER0_DIV)      |
224                 IO_STATE(R_TIMER_CTRL, i1,        nop)      |
225                 IO_STATE(R_TIMER_CTRL, tm1,       stop_ld)  |
226                 IO_STATE(R_TIMER_CTRL, clksel1,   c19k2Hz)  |
227                 IO_STATE(R_TIMER_CTRL, i0,        nop)      |
228                 IO_STATE(R_TIMER_CTRL, tm0,       stop_ld)  |
229                 IO_STATE(R_TIMER_CTRL, clksel0,   flexible);
230 
231         *R_TIMER_CTRL = r_timer_ctrl_shadow =
232                 IO_FIELD(R_TIMER_CTRL, timerdiv1, 192)      |
233                 IO_FIELD(R_TIMER_CTRL, timerdiv0, TIMER0_DIV)      |
234                 IO_STATE(R_TIMER_CTRL, i1,        nop)      |
235                 IO_STATE(R_TIMER_CTRL, tm1,       run)      |
236                 IO_STATE(R_TIMER_CTRL, clksel1,   c19k2Hz)  |
237                 IO_STATE(R_TIMER_CTRL, i0,        nop)      |
238                 IO_STATE(R_TIMER_CTRL, tm0,       run)      |
239                 IO_STATE(R_TIMER_CTRL, clksel0,   flexible);
240 
241         *R_TIMER_PRESCALE = PRESCALE_VALUE;
242 #endif
243 
244         /* unmask the timer irq */
245         *R_IRQ_MASK0_SET = IO_STATE(R_IRQ_MASK0_SET, timer0, set);
246 
247         /* now actually register the irq handler that calls timer_interrupt() */
248         setup_irq(2, &irq2); /* irq 2 is the timer0 irq in etrax */
249 
250         /* enable watchdog if we should use one */
251 #if defined(CONFIG_ETRAX_WATCHDOG)
252         printk("Enabling watchdog...\n");
253         start_watchdog();
254 
255         /* If we use the hardware watchdog, we want to trap it as an NMI
256            and dump registers before it resets us.  For this to happen, we
257            must set the "m" NMI enable flag (which once set, is unset only
258            when an NMI is taken).
259 
260            The same goes for the external NMI, but that doesn't have any
261            driver or infrastructure support yet.  */
262         asm ("setf m");
263 
264         *R_IRQ_MASK0_SET = IO_STATE(R_IRQ_MASK0_SET, watchdog_nmi, set);
265         *R_VECT_MASK_SET = IO_STATE(R_VECT_MASK_SET, nmi, set);
266 #endif
267 }
268 

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