/* * GeekOS timer interrupt support * Copyright (c) 2001,2003 David H. Hovemeyer * Copyright (c) 2003, Jeffrey K. Hollingsworth * $Revision: 1.6 $ * * This is free software. You are permitted to use, * redistribute, and modify it as specified in the file "COPYING". */ #include #include #include #include #include #include #include #include /* JRL Add a cpu frequency measurement */ uint_t cpu_khz_freq; #define __SLOW_DOWN_IO "\noutb %%al,$0x80" #ifdef REALLY_SLOW_IO #define __FULL_SLOW_DOWN_IO __SLOW_DOWN_IO __SLOW_DOWN_IO __SLOW_DOWN_IO __SLOW_DOWN_IO #else #define __FULL_SLOW_DOWN_IO __SLOW_DOWN_IO #endif #define __OUT1(s,x) \ static inline void out##s(unsigned x value, unsigned short port) { #define __OUT2(s,s1,s2) \ __asm__ __volatile__ ("out" #s " %" s1 "0,%" s2 "1" #define __OUT(s,s1,x) \ __OUT1(s,x) __OUT2(s,s1,"w") : : "a" (value), "Nd" (port)); } \ __OUT1(s##_p,x) __OUT2(s,s1,"w") __FULL_SLOW_DOWN_IO : : "a" (value), "Nd" (port));} \ #define __IN1(s) \ static inline RETURN_TYPE in##s(unsigned short port) { RETURN_TYPE _v; #define __IN2(s,s1,s2) \ __asm__ __volatile__ ("in" #s " %" s2 "1,%" s1 "0" #define __IN(s,s1,i...) \ __IN1(s) __IN2(s,s1,"w") : "=a" (_v) : "Nd" (port) ,##i ); return _v; } \ __IN1(s##_p) __IN2(s,s1,"w") __FULL_SLOW_DOWN_IO : "=a" (_v) : "Nd" (port) ,##i ); return _v; } \ #define RETURN_TYPE unsigned char __IN(b,"") #undef RETURN_TYPE #define RETURN_TYPE unsigned short __IN(w,"") #undef RETURN_TYPE #define RETURN_TYPE unsigned int __IN(l,"") #undef RETURN_TYPE __OUT(b,"b",char) __OUT(w,"w",short) #if defined(__i386__) #define rdtscll(val) \ __asm__ __volatile__("rdtsc" : "=A" (val)) #elif defined(__x86_64__) #define rdtscll(val) do { \ unsigned int a,d; \ asm volatile("rdtsc" : "=a" (a), "=d" (d)); \ (val) = ((unsigned long)a) | (((unsigned long)d)<<32); \ } while(0) #endif #define do_div(n,base) ({ \ unsigned long __upper, __low, __high, __mod, __base; \ __base = (base); \ asm("":"=a" (__low), "=d" (__high):"A" (n)); \ __upper = __high; \ if (__high) { \ __upper = __high % (__base); \ __high = __high / (__base); \ } \ asm("divl %2":"=a" (__low), "=d" (__mod):"rm" (__base), "0" (__low), "1" (__upper)); \ asm("":"=A" (n):"a" (__low),"d" (__high)); \ __mod; \ }) /** * This uses the Programmable Interval Timer that is standard on all * PC-compatible systems to determine the time stamp counter frequency. * * This uses the speaker output (channel 2) of the PIT. This is better than * using the timer interrupt output because we can read the value of the * speaker with just one inb(), where we need three i/o operations for the * interrupt channel. We count how many ticks the TSC does in 50 ms. * * Returns the detected time stamp counter frequency in KHz. */ static unsigned int pit_calibrate_tsc(void) { uint_t khz = 0; ullong_t start, end; // unsigned long flags; unsigned long pit_tick_rate = 1193182UL; /* 1.193182 MHz */ // spin_lock_irqsave(&pit_lock, flags); outb((inb(0x61) & ~0x02) | 0x01, 0x61); outb(0xb0, 0x43); outb((pit_tick_rate / (1000 / 50)) & 0xff, 0x42); outb((pit_tick_rate / (1000 / 50)) >> 8, 0x42); // start = get_cycles_sync(); rdtscll(start); while ((inb(0x61) & 0x20) == 0); rdtscll(end); // end = get_cycles_sync(); // spin_unlock_irqrestore(&pit_lock, flags); // return (end - start) / 50; khz = end - start; ; return khz / 50; } /* END JRL */ /* * Global tick counter */ volatile ulong_t g_numTicks; /* * Number of times the spin loop can execute during one timer tick */ static int s_spinCountPerTick; /* * Number of ticks to wait before calibrating the delay loop. */ #define CALIBRATE_NUM_TICKS 3 /* * The default quantum; maximum number of ticks a thread can use before * we suspend it and choose another. */ #define DEFAULT_MAX_TICKS 4 /* * Settable quantum. */ int g_Quantum = DEFAULT_MAX_TICKS; /* * Ticks per second. * FIXME: should set this to something more reasonable, like 100. */ #define HZ 100 //#define TICKS_PER_SEC 18 /*#define DEBUG_TIMER */ #ifdef DEBUG_TIMER # define Debug(args...) Print(args) #else # define Debug(args...) #endif /* ---------------------------------------------------------------------- * Private functions * ---------------------------------------------------------------------- */ static void Timer_Interrupt_Handler(struct Interrupt_State* state) { struct Kernel_Thread* current = g_currentThread; Begin_IRQ(state); SerialPrint("Host Timer Interrupt Handler running\n"); /* Update global and per-thread number of ticks */ ++g_numTicks; ++current->numTicks; /* * If thread has been running for an entire quantum, * inform the interrupt return code that we want * to choose a new thread. */ if (current->numTicks >= g_Quantum) { g_needReschedule = true; } End_IRQ(state); } /* * Temporary timer interrupt handler used to calibrate * the delay loop. */ static void Timer_Calibrate(struct Interrupt_State* state) { Begin_IRQ(state); if (g_numTicks < CALIBRATE_NUM_TICKS) ++g_numTicks; else { /* * Now we can look at EAX, which reflects how many times * the loop has executed */ /*Print("Timer_Calibrate: eax==%d\n", state->eax);*/ s_spinCountPerTick = INT_MAX - state->eax; state->eax = 0; /* make the loop terminate */ } End_IRQ(state); } /* * Delay loop; spins for given number of iterations. */ static void Spin(int count) { /* * The assembly code is the logical equivalent of * while (count-- > 0) { // waste some time } * We rely on EAX being used as the counter * variable. */ int result; __asm__ __volatile__ ( "1: decl %%eax\n\t" "cmpl $0, %%eax\n\t" "nop; nop; nop; nop; nop; nop\n\t" "nop; nop; nop; nop; nop; nop\n\t" "jg 1b" : "=a" (result) : "a" (count) ); } /* * Calibrate the delay loop. * This will initialize s_spinCountPerTick, which indicates * how many iterations of the loop are executed per timer tick. */ static void Calibrate_Delay(void) { Disable_Interrupts(); /* Install temporarily interrupt handler */ Install_IRQ(TIMER_IRQ, &Timer_Calibrate); Enable_IRQ(TIMER_IRQ); Enable_Interrupts(); /* Wait a few ticks */ while (g_numTicks < CALIBRATE_NUM_TICKS) ; /* * Execute the spin loop.xs * The temporary interrupt handler will overwrite the * loop counter when the next tick occurs. */ Spin(INT_MAX); Disable_Interrupts(); /* * Mask out the timer IRQ again, * since we will be installing a real timer interrupt handler. */ Disable_IRQ(TIMER_IRQ); Enable_Interrupts(); } /* ---------------------------------------------------------------------- * Public functions * ---------------------------------------------------------------------- */ void Init_Timer(void) { ushort_t foo = 1193182L / HZ; cpu_khz_freq = pit_calibrate_tsc(); PrintBoth("CPU KHZ=%lu\n", (ulong_t)cpu_khz_freq); PrintBoth("Initializing timer and setting to %d Hz...\n",HZ); /* Calibrate for delay loop */ Calibrate_Delay(); PrintBoth("Delay loop: %d iterations per tick\n", s_spinCountPerTick); // Set Timer to HZ Out_Byte(0x43,0x36); // channel 0, LSB/MSB, mode 3, binary Out_Byte(0x40, foo & 0xff); // LSB Out_Byte(0x40, foo >>8); // MSB /* Install an interrupt handler for the timer IRQ */ Install_IRQ(TIMER_IRQ, &Timer_Interrupt_Handler); Enable_IRQ(TIMER_IRQ); } #define US_PER_TICK (HZ * 1000000) /* * Spin for at least given number of microseconds. * FIXME: I'm sure this implementation leaves a lot to * be desired. */ void Micro_Delay(int us) { int num = us * s_spinCountPerTick; int denom = US_PER_TICK; int numSpins = num / denom; int rem = num % denom; if (rem > 0) ++numSpins; Debug("Micro_Delay(): num=%d, denom=%d, spin count = %d\n", num, denom, numSpins); Spin(numSpins); }