source: rtems/cpukit/score/cpu/powerpc/rtems/score/cpu.h @ b7c7b75b

/**
 * @file rtems/score/cpu.h
 */

/*
 * $Id$
 */
 
#ifndef _RTEMS_SCORE_CPU_H
#define _RTEMS_SCORE_CPU_H

#include <rtems/score/powerpc.h>              /* pick up machine definitions */
#ifndef ASM
#include <rtems/score/types.h>
#endif

/* conditional compilation parameters */

/*
 *  Should the calls to _Thread_Enable_dispatch be inlined?
 *
 *  If TRUE, then they are inlined.
 *  If FALSE, then a subroutine call is made.
 *
 *  Basically this is an example of the classic trade-off of size
 *  versus speed.  Inlining the call (TRUE) typically increases the
 *  size of RTEMS while speeding up the enabling of dispatching.
 *  [NOTE: In general, the _Thread_Dispatch_disable_level will
 *  only be 0 or 1 unless you are in an interrupt handler and that
 *  interrupt handler invokes the executive.]  When not inlined
 *  something calls _Thread_Enable_dispatch which in turns calls
 *  _Thread_Dispatch.  If the enable dispatch is inlined, then
 *  one subroutine call is avoided entirely.]
 */

#define CPU_INLINE_ENABLE_DISPATCH       FALSE

/*
 *  Should the body of the search loops in _Thread_queue_Enqueue_priority
 *  be unrolled one time?  In unrolled each iteration of the loop examines
 *  two "nodes" on the chain being searched.  Otherwise, only one node
 *  is examined per iteration.
 *
 *  If TRUE, then the loops are unrolled.
 *  If FALSE, then the loops are not unrolled.
 *
 *  The primary factor in making this decision is the cost of disabling
 *  and enabling interrupts (_ISR_Flash) versus the cost of rest of the
 *  body of the loop.  On some CPUs, the flash is more expensive than
 *  one iteration of the loop body.  In this case, it might be desirable
 *  to unroll the loop.  It is important to note that on some CPUs, this
 *  code is the longest interrupt disable period in RTEMS.  So it is
 *  necessary to strike a balance when setting this parameter.
 */

#define CPU_UNROLL_ENQUEUE_PRIORITY      FALSE

/*
 *  Processor defined structures required for cpukit/score.
 */

/*
 * Contexts
 *
 *  Generally there are 2 types of context to save.
 *     1. Interrupt registers to save
 *     2. Task level registers to save
 *
 *  This means we have the following 3 context items:
 *     1. task level context stuff::  Context_Control
 *     2. floating point task stuff:: Context_Control_fp
 *     3. special interrupt level context :: Context_Control_interrupt
 *
 *  On some processors, it is cost-effective to save only the callee
 *  preserved registers during a task context switch.  This means
 *  that the ISR code needs to save those registers which do not
 *  persist across function calls.  It is not mandatory to make this
 *  distinctions between the caller/callee saves registers for the
 *  purpose of minimizing context saved during task switch and on interrupts.
 *  If the cost of saving extra registers is minimal, simplicity is the
 *  choice.  Save the same context on interrupt entry as for tasks in
 *  this case.
 *
 *  Additionally, if gdb is to be made aware of RTEMS tasks for this CPU, then
 *  care should be used in designing the context area.
 *
 *  On some CPUs with hardware floating point support, the Context_Control_fp
 *  structure will not be used or it simply consist of an array of a
 *  fixed number of bytes.   This is done when the floating point context
 *  is dumped by a "FP save context" type instruction and the format
 *  is not really defined by the CPU.  In this case, there is no need
 *  to figure out the exact format -- only the size.  Of course, although
 *  this is enough information for RTEMS, it is probably not enough for
 *  a debugger such as gdb.  But that is another problem.
 */

#ifndef ASM
typedef struct {
    uint32_t   gpr1;    /* Stack pointer for all */
    uint32_t   gpr2;    /* Reserved SVR4, section ptr EABI + */
    uint32_t   gpr13;   /* Section ptr SVR4/EABI */
    uint32_t   gpr14;   /* Non volatile for all */
    uint32_t   gpr15;   /* Non volatile for all */
    uint32_t   gpr16;   /* Non volatile for all */
    uint32_t   gpr17;   /* Non volatile for all */
    uint32_t   gpr18;   /* Non volatile for all */
    uint32_t   gpr19;   /* Non volatile for all */
    uint32_t   gpr20;   /* Non volatile for all */
    uint32_t   gpr21;   /* Non volatile for all */
    uint32_t   gpr22;   /* Non volatile for all */
    uint32_t   gpr23;   /* Non volatile for all */
    uint32_t   gpr24;   /* Non volatile for all */
    uint32_t   gpr25;   /* Non volatile for all */
    uint32_t   gpr26;   /* Non volatile for all */
    uint32_t   gpr27;   /* Non volatile for all */
    uint32_t   gpr28;   /* Non volatile for all */
    uint32_t   gpr29;   /* Non volatile for all */
    uint32_t   gpr30;   /* Non volatile for all */
    uint32_t   gpr31;   /* Non volatile for all */
    uint32_t   cr;      /* PART of the CR is non volatile for all */
    uint32_t   pc;      /* Program counter/Link register */
    uint32_t   msr;     /* Initial interrupt level */
} Context_Control;

typedef struct {
    /* The ABIs (PowerOpen/SVR4/EABI) only require saving f14-f31 over
     * procedure calls.  However, this would mean that the interrupt
     * frame had to hold f0-f13, and the fpscr.  And as the majority
     * of tasks will not have an FP context, we will save the whole
     * context here.
     */
#if (PPC_HAS_DOUBLE == 1)
    double      f[32];
    double      fpscr;
#else
    float       f[32];
    float       fpscr;
#endif
} Context_Control_fp;
#endif /* ASM */

#ifndef ASM
typedef struct CPU_Interrupt_frame {
    uint32_t   stacklink;       /* Ensure this is a real frame (also reg1 save) */
    uint32_t   calleeLr;        /* link register used by callees: SVR4/EABI */

    /* This is what is left out of the primary contexts */
    uint32_t   gpr0;
    uint32_t   gpr2;            /* play safe */
    uint32_t   gpr3;
    uint32_t   gpr4;
    uint32_t   gpr5;
    uint32_t   gpr6;
    uint32_t   gpr7;
    uint32_t   gpr8;
    uint32_t   gpr9;
    uint32_t   gpr10;
    uint32_t   gpr11;
    uint32_t   gpr12;
    uint32_t   gpr13;   /* Play safe */
    uint32_t   gpr28;   /* For internal use by the IRQ handler */
    uint32_t   gpr29;   /* For internal use by the IRQ handler */
    uint32_t   gpr30;   /* For internal use by the IRQ handler */
    uint32_t   gpr31;   /* For internal use by the IRQ handler */
    uint32_t   cr;      /* Bits of this are volatile, so no-one may save */
    uint32_t   ctr;
    uint32_t   xer;
    uint32_t   lr;
    uint32_t   pc;
    uint32_t   msr;
    uint32_t   pad[3];
} CPU_Interrupt_frame;
#endif /* ASM */

#ifdef _OLD_EXCEPTIONS
#include <rtems/old-exceptions/cpu.h>
#else
#include <rtems/new-exceptions/cpu.h>
#endif

/*
 *  Should be large enough to run all RTEMS tests.  This insures
 *  that a "reasonable" small application should not have any problems.
 */

#define CPU_STACK_MINIMUM_SIZE          (1024*8)

/*
 *  CPU's worst alignment requirement for data types on a byte boundary.  This
 *  alignment does not take into account the requirements for the stack.
 */

#define CPU_ALIGNMENT              (PPC_ALIGNMENT)

/*
 *  This number corresponds to the byte alignment requirement for the
 *  heap handler.  This alignment requirement may be stricter than that
 *  for the data types alignment specified by CPU_ALIGNMENT.  It is
 *  common for the heap to follow the same alignment requirement as
 *  CPU_ALIGNMENT.  If the CPU_ALIGNMENT is strict enough for the heap,
 *  then this should be set to CPU_ALIGNMENT.
 *
 *  NOTE:  This does not have to be a power of 2.  It does have to
 *         be greater or equal to than CPU_ALIGNMENT.
 */

#define CPU_HEAP_ALIGNMENT         (PPC_ALIGNMENT)

/*
 *  This number corresponds to the byte alignment requirement for memory
 *  buffers allocated by the partition manager.  This alignment requirement
 *  may be stricter than that for the data types alignment specified by
 *  CPU_ALIGNMENT.  It is common for the partition to follow the same
 *  alignment requirement as CPU_ALIGNMENT.  If the CPU_ALIGNMENT is strict
 *  enough for the partition, then this should be set to CPU_ALIGNMENT.
 *
 *  NOTE:  This does not have to be a power of 2.  It does have to
 *         be greater or equal to than CPU_ALIGNMENT.
 */

#define CPU_PARTITION_ALIGNMENT    (PPC_ALIGNMENT)

/*
 *  This number corresponds to the byte alignment requirement for the
 *  stack.  This alignment requirement may be stricter than that for the
 *  data types alignment specified by CPU_ALIGNMENT.  If the CPU_ALIGNMENT
 *  is strict enough for the stack, then this should be set to 0.
 *
 *  NOTE:  This must be a power of 2 either 0 or greater than CPU_ALIGNMENT.
 */

#define CPU_STACK_ALIGNMENT        (PPC_STACK_ALIGNMENT)

#ifndef ASM
/*  The following routine swaps the endian format of an unsigned int.
 *  It must be static because it is referenced indirectly.
 *
 *  This version will work on any processor, but if there is a better
 *  way for your CPU PLEASE use it.  The most common way to do this is to:
 *
 *     swap least significant two bytes with 16-bit rotate
 *     swap upper and lower 16-bits
 *     swap most significant two bytes with 16-bit rotate
 *
 *  Some CPUs have special instructions which swap a 32-bit quantity in
 *  a single instruction (e.g. i486).  It is probably best to avoid
 *  an "endian swapping control bit" in the CPU.  One good reason is
 *  that interrupts would probably have to be disabled to insure that
 *  an interrupt does not try to access the same "chunk" with the wrong
 *  endian.  Another good reason is that on some CPUs, the endian bit
 *  endianness for ALL fetches -- both code and data -- so the code
 *  will be fetched incorrectly.
 */
 
static inline uint32_t CPU_swap_u32(
  uint32_t value
)
{
  uint32_t   swapped;
 
  asm volatile("rlwimi %0,%1,8,24,31;"
               "rlwimi %0,%1,24,16,23;"
               "rlwimi %0,%1,8,8,15;"
               "rlwimi %0,%1,24,0,7;" :
               "=&r" ((swapped)) : "r" ((value)));

  return( swapped );
}

#define CPU_swap_u16( value ) \
  (((value&0xff) << 8) | ((value >> 8)&0xff))

#endif /* ASM */

#ifndef ASM
/*
 *  Macros to access PowerPC specific additions to the CPU Table
 */

#define rtems_cpu_configuration_get_clicks_per_usec() \
   (_CPU_Table.clicks_per_usec)

#define rtems_cpu_configuration_get_exceptions_in_ram() \
   (_CPU_Table.exceptions_in_RAM)

#endif /* ASM */

#ifndef ASM
/*
 *  Simple spin delay in microsecond units for device drivers.
 *  This is very dependent on the clock speed of the target.
 */

#define CPU_Get_timebase_low( _value ) \
    asm volatile( "mftb  %0" : "=r" (_value) )

#define rtems_bsp_delay( _microseconds ) \
  do { \
    uint32_t   start, ticks, now; \
    CPU_Get_timebase_low( start ) ; \
    ticks = (_microseconds) * rtems_cpu_configuration_get_clicks_per_usec(); \
    do \
      CPU_Get_timebase_low( now ) ; \
    while (now - start < ticks); \
  } while (0)

#define rtems_bsp_delay_in_bus_cycles( _cycles ) \
  do { \
    uint32_t   start, now; \
    CPU_Get_timebase_low( start ); \
    do \
      CPU_Get_timebase_low( now ); \
    while (now - start < (_cycles)); \
  } while (0)

#endif /* ASM */

#ifndef ASM
/*
 *  Routines to access the decrementer register
 */

#define PPC_Set_decrementer( _clicks ) \
  do { \
    asm volatile( "mtdec %0" : : "r" ((_clicks)) ); \
  } while (0)

#define PPC_Get_decrementer( _clicks ) \
    asm volatile( "mfdec  %0" : "=r" (_clicks) )

#endif /* ASM */

#ifndef ASM
/*
 *  Routines to access the time base register
 */

static inline uint64_t PPC_Get_timebase_register( void )
{
  uint32_t tbr_low;
  uint32_t tbr_high;
  uint32_t tbr_high_old;
  uint64_t tbr;

  do {
    asm volatile( "mftbu %0" : "=r" (tbr_high_old));
    asm volatile( "mftb  %0" : "=r" (tbr_low));
    asm volatile( "mftbu %0" : "=r" (tbr_high));
  } while ( tbr_high_old != tbr_high );

  tbr = tbr_high;
  tbr <<= 32;
  tbr |= tbr_low;
  return tbr;
}

static inline  void PPC_Set_timebase_register (uint64_t tbr)
{
  uint32_t tbr_low;
  uint32_t tbr_high;

  tbr_low = (tbr & 0xffffffff) ;
  tbr_high = (tbr >> 32) & 0xffffffff;
  asm volatile( "mtspr 284, %0" : : "r" (tbr_low));
  asm volatile( "mtspr 285, %0" : : "r" (tbr_high));
  
}
#endif /* ASM */

#ifndef ASM
/* Context handler macros */

/*
 *  Initialize the context to a state suitable for starting a
 *  task after a context restore operation.  Generally, this
 *  involves:
 *
 *     - setting a starting address
 *     - preparing the stack
 *     - preparing the stack and frame pointers
 *     - setting the proper interrupt level in the context
 *     - initializing the floating point context
 *
 *  This routine generally does not set any unnecessary register
 *  in the context.  The state of the "general data" registers is
 *  undefined at task start time.
 */

void _CPU_Context_Initialize(
  Context_Control  *the_context,
  uint32_t         *stack_base,
  uint32_t          size,
  uint32_t          new_level,
  void             *entry_point,
  boolean           is_fp
);

/*
 *  This routine is responsible for somehow restarting the currently
 *  executing task.  If you are lucky, then all that is necessary
 *  is restoring the context.  Otherwise, there will need to be
 *  a special assembly routine which does something special in this
 *  case.  Context_Restore should work most of the time.  It will
 *  not work if restarting self conflicts with the stack frame
 *  assumptions of restoring a context.
 */

#define _CPU_Context_Restart_self( _the_context ) \
   _CPU_Context_restore( (_the_context) );

/*
 *  The purpose of this macro is to allow the initial pointer into
 *  a floating point context area (used to save the floating point
 *  context) to be at an arbitrary place in the floating point
 *  context area.
 *
 *  This is necessary because some FP units are designed to have
 *  their context saved as a stack which grows into lower addresses.
 *  Other FP units can be saved by simply moving registers into offsets
 *  from the base of the context area.  Finally some FP units provide
 *  a "dump context" instruction which could fill in from high to low
 *  or low to high based on the whim of the CPU designers.
 */

#define _CPU_Context_Fp_start( _base, _offset ) \
   ( (void *) _Addresses_Add_offset( (_base), (_offset) ) )

/*
 *  This routine initializes the FP context area passed to it to.
 *  There are a few standard ways in which to initialize the
 *  floating point context.  The code included for this macro assumes
 *  that this is a CPU in which a "initial" FP context was saved into
 *  _CPU_Null_fp_context and it simply copies it to the destination
 *  context passed to it.
 *
 *  Other models include (1) not doing anything, and (2) putting
 *  a "null FP status word" in the correct place in the FP context.
 */

#define _CPU_Context_Initialize_fp( _destination ) \
  { \
   ((Context_Control_fp *) *((void **) _destination))->fpscr = PPC_INIT_FPSCR; \
  }

/* end of Context handler macros */
#endif /* ASM */

#ifndef ASM
/* Bitfield handler macros */

/*
 *  This routine sets _output to the bit number of the first bit
 *  set in _value.  _value is of CPU dependent type Priority_Bit_map_control.
 *  This type may be either 16 or 32 bits wide although only the 16
 *  least significant bits will be used.
 *
 *  There are a number of variables in using a "find first bit" type
 *  instruction.
 *
 *    (1) What happens when run on a value of zero?
 *    (2) Bits may be numbered from MSB to LSB or vice-versa.
 *    (3) The numbering may be zero or one based.
 *    (4) The "find first bit" instruction may search from MSB or LSB.
 *
 *  RTEMS guarantees that (1) will never happen so it is not a concern.
 *  (2),(3), (4) are handled by the macros _CPU_Priority_mask() and
 *  _CPU_Priority_Bits_index().  These three form a set of routines
 *  which must logically operate together.  Bits in the _value are
 *  set and cleared based on masks built by _CPU_Priority_mask().
 *  The basic major and minor values calculated by _Priority_Major()
 *  and _Priority_Minor() are "massaged" by _CPU_Priority_Bits_index()
 *  to properly range between the values returned by the "find first bit"
 *  instruction.  This makes it possible for _Priority_Get_highest() to
 *  calculate the major and directly index into the minor table.
 *  This mapping is necessary to ensure that 0 (a high priority major/minor)
 *  is the first bit found.
 *
 *  This entire "find first bit" and mapping process depends heavily
 *  on the manner in which a priority is broken into a major and minor
 *  components with the major being the 4 MSB of a priority and minor
 *  the 4 LSB.  Thus (0 << 4) + 0 corresponds to priority 0 -- the highest
 *  priority.  And (15 << 4) + 14 corresponds to priority 254 -- the next
 *  to the lowest priority.
 *
 *  If your CPU does not have a "find first bit" instruction, then
 *  there are ways to make do without it.  Here are a handful of ways
 *  to implement this in software:
 *
 *    - a series of 16 bit test instructions
 *    - a "binary search using if's"
 *    - _number = 0
 *      if _value > 0x00ff
 *        _value >>=8
 *        _number = 8;
 *
 *      if _value > 0x0000f
 *        _value >=8
 *        _number += 4
 *
 *      _number += bit_set_table[ _value ]
 *
 *    where bit_set_table[ 16 ] has values which indicate the first
 *      bit set
 */

#define _CPU_Bitfield_Find_first_bit( _value, _output ) \
  { \
    asm volatile ("cntlzw %0, %1" : "=r" ((_output)), "=r" ((_value)) : \
                  "1" ((_value))); \
  }

/* end of Bitfield handler macros */

/*
 *  This routine builds the mask which corresponds to the bit fields
 *  as searched by _CPU_Bitfield_Find_first_bit().  See the discussion
 *  for that routine.
 */

#define _CPU_Priority_Mask( _bit_number ) \
  ( 0x80000000 >> (_bit_number) )

/*
 *  This routine translates the bit numbers returned by
 *  _CPU_Bitfield_Find_first_bit() into something suitable for use as
 *  a major or minor component of a priority.  See the discussion
 *  for that routine.
 */

#define _CPU_Priority_bits_index( _priority ) \
  (_priority)

/* end of Priority handler macros */
#endif /* ASM */

/* functions */

#ifndef ASM

/*
 *  _CPU_Initialize
 *
 *  This routine performs CPU dependent initialization.
 */

void _CPU_Initialize(
  rtems_cpu_table  *cpu_table,
  void            (*thread_dispatch)
);

/*
 *  _CPU_ISR_install_vector
 *
 *  This routine installs an interrupt vector.
 */

void _CPU_ISR_install_vector(
  uint32_t    vector,
  proc_ptr    new_handler,
  proc_ptr   *old_handler
);

/*
 *  _CPU_Install_interrupt_stack
 *
 *  This routine installs the hardware interrupt stack pointer.
 *
 *  NOTE:  It need only be provided if CPU_HAS_HARDWARE_INTERRUPT_STACK
 *         is TRUE.
 */

void _CPU_Install_interrupt_stack( void );

/*
 *  _CPU_Context_switch
 *
 *  This routine switches from the run context to the heir context.
 */

void _CPU_Context_switch(
  Context_Control  *run,
  Context_Control  *heir
);

/*
 *  _CPU_Context_restore
 *
 *  This routine is generallu used only to restart self in an
 *  efficient manner.  It may simply be a label in _CPU_Context_switch.
 *
 *  NOTE: May be unnecessary to reload some registers.
 */

void _CPU_Context_restore(
  Context_Control *new_context
);

/*
 *  _CPU_Context_save_fp
 *
 *  This routine saves the floating point context passed to it.
 */

void _CPU_Context_save_fp(
  void **fp_context_ptr
);

/*
 *  _CPU_Context_restore_fp
 *
 *  This routine restores the floating point context passed to it.
 */

void _CPU_Context_restore_fp(
  void **fp_context_ptr
);

void _CPU_Fatal_error(
  uint32_t   _error
);

#endif /* ASM */

#endif /* _RTEMS_SCORE_CPU_H */