rockbox/firmware/thread.c

/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * Copyright (C) 2002 by Ulf Ralberg
 *
 * All files in this archive are subject to the GNU General Public License.
 * See the file COPYING in the source tree root for full license agreement.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/
#include <stdbool.h>
#include "thread.h"
#include "panic.h"
#include "kernel.h"
#include "sh7034.h"

struct regs
{
    unsigned int  r[7]; /* Registers r8 thru r14 */
    void          *sp;  /* Stack pointer (r15) */
    unsigned int  mach;
    unsigned int  macl;
    unsigned int  sr;   /* Status register */
    void*         pr;   /* Procedure register */
};

int num_threads;
static volatile int num_sleepers;
static int current_thread;
static struct regs thread_contexts[MAXTHREADS] __attribute__ ((section(".idata")));
const char *thread_name[MAXTHREADS];
void *thread_stack[MAXTHREADS];
int thread_stack_size[MAXTHREADS];
static const char main_thread_name[] = "main";

extern int stackbegin[];
extern int stackend[];

void switch_thread(void) __attribute__ ((section(".icode")));

/*--------------------------------------------------------------------------- 
 * Store non-volatile context.
 *---------------------------------------------------------------------------
 */
static inline void store_context(void* addr)
{
    asm volatile ("add #48, %0\n\t"
                  "sts.l pr,  @-%0\n\t"
                  "stc.l sr,  @-%0\n\t"
                  "sts.l macl,@-%0\n\t"
                  "sts.l mach,@-%0\n\t"
                  "mov.l r15, @-%0\n\t"
                  "mov.l r14, @-%0\n\t"
                  "mov.l r13, @-%0\n\t"
                  "mov.l r12, @-%0\n\t"
                  "mov.l r11, @-%0\n\t"
                  "mov.l r10, @-%0\n\t"
                  "mov.l r9,  @-%0\n\t"
                  "mov.l r8,  @-%0" : : "r" (addr));
}

/*--------------------------------------------------------------------------- 
 * Load non-volatile context.
 *---------------------------------------------------------------------------
 */
static inline void load_context(const void* addr)
{
    asm volatile ("mov.l @%0+,r8\n\t"
                  "mov.l @%0+,r9\n\t"
                  "mov.l @%0+,r10\n\t"
                  "mov.l @%0+,r11\n\t"
                  "mov.l @%0+,r12\n\t"
                  "mov.l @%0+,r13\n\t"
                  "mov.l @%0+,r14\n\t"
                  "mov.l @%0+,r15\n\t"
                  "lds.l @%0+,mach\n\t"
                  "lds.l @%0+,macl\n\t"
                  "ldc.l @%0+,sr\n\t"
                  "mov.l @%0,%0\n\t"
                  "lds %0,pr\n\t"
                  "mov.l %0, @(0, r15)" : "+r" (addr));
}

/*--------------------------------------------------------------------------- 
 * Switch thread in round robin fashion.
 *---------------------------------------------------------------------------
 */
void switch_thread(void)
{
    int current;
    int next;
    unsigned int *stackptr;

#ifdef SIMULATOR
    /* Do nothing */
#else

    while (num_sleepers == num_threads)
    {
        /* Enter sleep mode, woken up on interrupt */
        SBYCR &= 0x7F;
        asm volatile ("sleep");
    }
    
#endif
    next = current = current_thread;

    if (++next >= num_threads)
        next = 0;
    current_thread = next;
    store_context(&thread_contexts[current]);
    
    /* Check if the current thread stack is overflown */
    stackptr = thread_stack[current];
    if(stackptr[0] != 0xdeadbeef)
       panicf("Stkov %s", thread_name[current]);
       
    load_context(&thread_contexts[next]);
}

void sleep_thread(void)
{
    ++num_sleepers;
    switch_thread();
}

void wake_up_thread(void)
{
    num_sleepers = 0;
}

/*--------------------------------------------------------------------------- 
 * Create thread.
 * Return ID if context area could be allocated, else -1.
 *---------------------------------------------------------------------------
 */
int create_thread(void* function, void* stack, int stack_size,
                  const char *name)
{
   unsigned int i;
   unsigned int stacklen;
   unsigned int *stackptr;
   struct regs *regs;
        
   if (num_threads >= MAXTHREADS)
      return -1;

   /* Munge the stack to make it easy to spot stack overflows */
   stacklen = stack_size / 4;
   stackptr = stack;
   for(i = 0;i < stacklen;i++)
   {
      stackptr[i] = 0xdeadbeef;
   }

   /* Store interesting information */
   thread_name[num_threads] = name;
   thread_stack[num_threads] = stack;
   thread_stack_size[num_threads] = stack_size;
   regs = &thread_contexts[num_threads];
   store_context(regs);
   /* Subtract 4 to leave room for the PR push in load_context()
      Align it on an even 32 bit boundary */
   regs->sp = (void*)(((unsigned int)stack + stack_size - 4) & ~3);
   regs->sr = 0;
   regs->pr = function;

   wake_up_thread();
   return num_threads++; /* return the current ID, e.g for remove_thread() */
}

/*--------------------------------------------------------------------------- 
 * Remove a thread from the scheduler.
 * Parameter is the ID as returned from create_thread().
 *---------------------------------------------------------------------------
 */
void remove_thread(int threadnum)
{
    int i;

    if(threadnum >= num_threads)
       return;

    num_threads--;
    for (i=threadnum; i<num_threads-1; i++)
    {   /* move all entries which are behind */
        thread_name[i]       = thread_name[i+1];
        thread_stack[i]      = thread_stack[i+1];
        thread_stack_size[i] = thread_stack_size[i+1];
        thread_contexts[i]   = thread_contexts[i+1];
    }

    if (current_thread == threadnum) /* deleting the current one? */
        current_thread = num_threads; /* set beyond last, avoid store harm */
    else if (current_thread > threadnum) /* within the moved positions? */
        current_thread--; /* adjust it, point to same context again */
}

void init_threads(void)
{
    num_threads = 1; /* We have 1 thread to begin with */
    current_thread = 0; /* The current thread is number 0 */
    thread_name[0] = main_thread_name;
    thread_stack[0] = stackbegin;
    thread_stack_size[0] = (int)stackend - (int)stackbegin;
    num_sleepers = 0;
}

int thread_stack_usage(int threadnum)
{
   unsigned int i;
   unsigned int *stackptr = thread_stack[threadnum];

   if(threadnum >= num_threads)
      return -1;
   
   for(i = 0;i < thread_stack_size[threadnum]/sizeof(int);i++)
   {
      if(stackptr[i] != 0xdeadbeef)
         break;
   }
   
   return ((thread_stack_size[threadnum] - i * 4) * 100) /
      thread_stack_size[threadnum];
}