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/*

 *  This include file contains information pertaining to the Hitachi SH

 *  processor.

 *

 *  Authors: Ralf Corsepius (corsepiu@faw.uni-ulm.de) and

 *           Bernd Becker (becker@faw.uni-ulm.de)

 *

 *  COPYRIGHT (c) 1997-1998, FAW Ulm, Germany

 *

 *  This program is distributed in the hope that it will be useful,

 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

 *

 *

 *  COPYRIGHT (c) 1998.

 *  On-Line Applications Research Corporation (OAR).

 *  Copyright assigned to U.S. Government, 1994.

 *

 *  The license and distribution terms for this file may be

 *  found in the file LICENSE in this distribution or at

 *  http://www.OARcorp.com/rtems/license.html.

 *

 *  $Id: cpu.h,v 1.2 2001-09-27 11:59:30 chris Exp $

 */

#ifndef _SH_CPU_h

#define _SH_CPU_h

#ifdef __cplusplus

extern "C" {

#endif

#include <rtems/score/sh.h>              /* pick up machine definitions */

#ifndef ASM

#include <rtems/score/shtypes.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      TRUE

/*

 *  Does RTEMS manage a dedicated interrupt stack in software?

 *

 *  If TRUE, then a stack is allocated in _ISR_Handler_initialization.

 *  If FALSE, nothing is done.

 *

 *  If the CPU supports a dedicated interrupt stack in hardware,

 *  then it is generally the responsibility of the BSP to allocate it

 *  and set it up.

 *

 *  If the CPU does not support a dedicated interrupt stack, then

 *  the porter has two options: (1) execute interrupts on the

 *  stack of the interrupted task, and (2) have RTEMS manage a dedicated

 *  interrupt stack.

 *

 *  If this is TRUE, CPU_ALLOCATE_INTERRUPT_STACK should also be TRUE.

 *

 *  Only one of CPU_HAS_SOFTWARE_INTERRUPT_STACK and

 *  CPU_HAS_HARDWARE_INTERRUPT_STACK should be set to TRUE.  It is

 *  possible that both are FALSE for a particular CPU.  Although it

 *  is unclear what that would imply about the interrupt processing

 *  procedure on that CPU.

 */

#define CPU_HAS_SOFTWARE_INTERRUPT_STACK TRUE

#define CPU_HAS_HARDWARE_INTERRUPT_STACK FALSE

/*

 * We define the interrupt stack in the linker script

 */

#define CPU_ALLOCATE_INTERRUPT_STACK FALSE 

/*

 *  Does the RTEMS invoke the user's ISR with the vector number and

 *  a pointer to the saved interrupt frame (1) or just the vector

 *  number (0)?

 */

#define CPU_ISR_PASSES_FRAME_POINTER 0

/*

 *  Does the CPU have hardware floating point?

 *

 *  If TRUE, then the RTEMS_FLOATING_POINT task attribute is supported.

 *  If FALSE, then the RTEMS_FLOATING_POINT task attribute is ignored.

 *

 *  We currently support sh1 only, which has no FPU, other SHes have an FPU

 *

 *  The macro name "NO_CPU_HAS_FPU" should be made CPU specific.

 *  It indicates whether or not this CPU model has FP support.  For

 *  example, it would be possible to have an i386_nofp CPU model

 *  which set this to false to indicate that you have an i386 without

 *  an i387 and wish to leave floating point support out of RTEMS.

 */

#define CPU_HARDWARE_FP     FALSE

/*

 *  Are all tasks RTEMS_FLOATING_POINT tasks implicitly?

 *

 *  If TRUE, then the RTEMS_FLOATING_POINT task attribute is assumed.

 *  If FALSE, then the RTEMS_FLOATING_POINT task attribute is followed.

 *

 *  So far, the only CPU in which this option has been used is the

 *  HP PA-RISC.  The HP C compiler and gcc both implicitly use the

 *  floating point registers to perform integer multiplies.  If

 *  a function which you would not think utilize the FP unit DOES,

 *  then one can not easily predict which tasks will use the FP hardware.

 *  In this case, this option should be TRUE.

 *

 *  If CPU_HARDWARE_FP is FALSE, then this should be FALSE as well.

 */

#define CPU_ALL_TASKS_ARE_FP     FALSE

/*

 *  Should the IDLE task have a floating point context?

 *

 *  If TRUE, then the IDLE task is created as a RTEMS_FLOATING_POINT task

 *  and it has a floating point context which is switched in and out.

 *  If FALSE, then the IDLE task does not have a floating point context.

 *

 *  Setting this to TRUE negatively impacts the time required to preempt

 *  the IDLE task from an interrupt because the floating point context

 *  must be saved as part of the preemption.

 */

#define CPU_IDLE_TASK_IS_FP      FALSE

/*

 *  Should the saving of the floating point registers be deferred

 *  until a context switch is made to another different floating point

 *  task?

 *

 *  If TRUE, then the floating point context will not be stored until

 *  necessary.  It will remain in the floating point registers and not

 *  disturned until another floating point task is switched to.

 *

 *  If FALSE, then the floating point context is saved when a floating

 *  point task is switched out and restored when the next floating point

 *  task is restored.  The state of the floating point registers between

 *  those two operations is not specified.

 *

 *  If the floating point context does NOT have to be saved as part of

 *  interrupt dispatching, then it should be safe to set this to TRUE.

 *

 *  Setting this flag to TRUE results in using a different algorithm

 *  for deciding when to save and restore the floating point context.

 *  The deferred FP switch algorithm minimizes the number of times

 *  the FP context is saved and restored.  The FP context is not saved

 *  until a context switch is made to another, different FP task.

 *  Thus in a system with only one FP task, the FP context will never

 *  be saved or restored.

 */

#define CPU_USE_DEFERRED_FP_SWITCH       TRUE

/*

 *  Does this port provide a CPU dependent IDLE task implementation?

 *

 *  If TRUE, then the routine _CPU_Thread_Idle_body

 *  must be provided and is the default IDLE thread body instead of

 *  _CPU_Thread_Idle_body.

 *

 *  If FALSE, then use the generic IDLE thread body if the BSP does

 *  not provide one.

 *

 *  This is intended to allow for supporting processors which have

 *  a low power or idle mode.  When the IDLE thread is executed, then

 *  the CPU can be powered down.

 *

 *  The order of precedence for selecting the IDLE thread body is:

 *

 *    1.  BSP provided

 *    2.  CPU dependent (if provided)

 *    3.  generic (if no BSP and no CPU dependent)

 */

#define CPU_PROVIDES_IDLE_THREAD_BODY    TRUE

/*

 *  Does the stack grow up (toward higher addresses) or down

 *  (toward lower addresses)?

 *

 *  If TRUE, then the grows upward.

 *  If FALSE, then the grows toward smaller addresses.

 */

#define CPU_STACK_GROWS_UP               FALSE

/*

 *  The following is the variable attribute used to force alignment

 *  of critical RTEMS structures.  On some processors it may make

 *  sense to have these aligned on tighter boundaries than

 *  the minimum requirements of the compiler in order to have as

 *  much of the critical data area as possible in a cache line.

 *

 *  The placement of this macro in the declaration of the variables

 *  is based on the syntactically requirements of the GNU C

 *  "__attribute__" extension.  For example with GNU C, use

 *  the following to force a structures to a 32 byte boundary.

 *

 *      __attribute__ ((aligned (32)))

 *

 *  NOTE:  Currently only the Priority Bit Map table uses this feature.

 *         To benefit from using this, the data must be heavily

 *         used so it will stay in the cache and used frequently enough

 *         in the executive to justify turning this on.

 */

#define CPU_STRUCTURE_ALIGNMENT __attribute__ ((aligned(16)))

/*

 *  Define what is required to specify how the network to host conversion

 *  routines are handled.

 *

 *  NOTE: SHes can be big or little endian, the default is big endian

 */

#define CPU_HAS_OWN_HOST_TO_NETWORK_ROUTINES     FALSE

/* __LITTLE_ENDIAN__ is defined if -ml is given to gcc */

#if defined(__LITTLE_ENDIAN__)

#define CPU_BIG_ENDIAN                           FALSE

#define CPU_LITTLE_ENDIAN                        TRUE

#else

#define CPU_BIG_ENDIAN                           TRUE

#define CPU_LITTLE_ENDIAN                        FALSE

#endif

/*

 *  The following defines the number of bits actually used in the

 *  interrupt field of the task mode.  How those bits map to the

 *  CPU interrupt levels is defined by the routine _CPU_ISR_Set_level().

 */

#define CPU_MODES_INTERRUPT_MASK   0x0000000f

/*

 *  Processor defined structures

 *

 *  Examples structures include the descriptor tables from the i386

 *  and the processor control structure on the i960ca.

 */

/* may need to put some structures here.  */

/*

 * 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.

 */

typedef struct {

  unsigned32 *r15;      /* stack pointer */

  unsigned32 macl;

  unsigned32 mach;

  unsigned32 *pr;

  unsigned32 *r14;      /* frame pointer/call saved */

  unsigned32 r13;       /* call saved */

  unsigned32 r12;       /* call saved */

  unsigned32 r11;       /* call saved */

  unsigned32 r10;       /* call saved */

  unsigned32 r9;        /* call saved */

  unsigned32 r8;        /* call saved */

  unsigned32 *r7;       /* arg in */

  unsigned32 *r6;       /* arg in */

#if 0

  unsigned32 *r5;       /* arg in */

  unsigned32 *r4;       /* arg in */

#endif

  unsigned32 *r3;       /* scratch */

  unsigned32 *r2;       /* scratch */

  unsigned32 *r1;       /* scratch */

  unsigned32 *r0;       /* arg return */

  unsigned32 gbr;

  unsigned32 sr;

} Context_Control;

typedef struct {

} Context_Control_fp;

typedef struct {

} CPU_Interrupt_frame;

/*

 *  The following table contains the information required to configure

 *  the SH processor specific parameters.

 */

typedef struct {

  void       (*pretasking_hook)( void );

  void       (*predriver_hook)( void );

  void       (*postdriver_hook)( void );

  void       (*idle_task)( void );

  boolean      do_zero_of_workspace;

  unsigned32   idle_task_stack_size;

  unsigned32   interrupt_stack_size;

  unsigned32   extra_mpci_receive_server_stack;

  void *     (*stack_allocate_hook)( unsigned32 );

  void       (*stack_free_hook)( void* );

  /* end of fields required on all CPUs */

  unsigned32    clicks_per_second ; /* cpu frequency in Hz */

}   rtems_cpu_table;

/*

 *  Macros to access required entires in the CPU Table are in

 *  the file rtems/system.h.

 */

/*

 *  Macros to access SH specific additions to the CPU Table

 */

#define rtems_cpu_configuration_get_clicks_per_second() \

  (_CPU_Table.clicks_per_second)

/*

 *  This variable is optional.  It is used on CPUs on which it is difficult

 *  to generate an "uninitialized" FP context.  It is filled in by

 *  _CPU_Initialize and copied into the task's FP context area during

 *  _CPU_Context_Initialize.

 */

/*

SCORE_EXTERN Context_Control_fp  _CPU_Null_fp_context;

*/

/*

 *  On some CPUs, RTEMS supports a software managed interrupt stack.

 *  This stack is allocated by the Interrupt Manager and the switch

 *  is performed in _ISR_Handler.  These variables contain pointers

 *  to the lowest and highest addresses in the chunk of memory allocated

 *  for the interrupt stack.  Since it is unknown whether the stack

 *  grows up or down (in general), this give the CPU dependent

 *  code the option of picking the version it wants to use.

 *

 *  NOTE: These two variables are required if the macro

 *        CPU_HAS_SOFTWARE_INTERRUPT_STACK is defined as TRUE.

 */

SCORE_EXTERN void               *_CPU_Interrupt_stack_low;

SCORE_EXTERN void               *_CPU_Interrupt_stack_high;

/*

 *  With some compilation systems, it is difficult if not impossible to

 *  call a high-level language routine from assembly language.  This

 *  is especially true of commercial Ada compilers and name mangling

 *  C++ ones.  This variable can be optionally defined by the CPU porter

 *  and contains the address of the routine _Thread_Dispatch.  This

 *  can make it easier to invoke that routine at the end of the interrupt

 *  sequence (if a dispatch is necessary).

 */

SCORE_EXTERN void           (*_CPU_Thread_dispatch_pointer)();

/*

 *  Nothing prevents the porter from declaring more CPU specific variables.

 */

/* XXX: if needed, put more variables here */

SCORE_EXTERN void CPU_delay( unsigned32 microseconds );

/*

 *  The size of the floating point context area.  On some CPUs this

 *  will not be a "sizeof" because the format of the floating point

 *  area is not defined -- only the size is.  This is usually on

 *  CPUs with a "floating point save context" instruction.

 */

#define CPU_CONTEXT_FP_SIZE sizeof( Context_Control_fp )

/*

 *  Amount of extra stack (above minimum stack size) required by

 *  MPCI receive server thread.  Remember that in a multiprocessor

 *  system this thread must exist and be able to process all directives.

 */

#define CPU_MPCI_RECEIVE_SERVER_EXTRA_STACK 0

/*

 *  This defines the number of entries in the ISR_Vector_table managed

 *  by RTEMS.

 */

#define CPU_INTERRUPT_NUMBER_OF_VECTORS      256

#define CPU_INTERRUPT_MAXIMUM_VECTOR_NUMBER  (CPU_INTERRUPT_NUMBER_OF_VECTORS - 1)

/*

 *  Should be large enough to run all RTEMS tests.  This insures

 *  that a "reasonable" small application should not have any problems.

 *

 *  We have been able to run the sptests with this value, but have not

 *  been able to run the tmtest suite.

 */

#define CPU_STACK_MINIMUM_SIZE          4096

/*

 *  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              4

/*

 *  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         CPU_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    CPU_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        CPU_ALIGNMENT

/* ISR handler macros */

/*

 *  Disable all interrupts for an RTEMS critical section.  The previous

 *  level is returned in _level.

 */

#define _CPU_ISR_Disable( _level) \

  sh_disable_interrupts( _level )

/*

 *  Enable interrupts to the previous level (returned by _CPU_ISR_Disable).

 *  This indicates the end of an RTEMS critical section.  The parameter

 *  _level is not modified.

 */

#define _CPU_ISR_Enable( _level) \

   sh_enable_interrupts( _level)

/*

 *  This temporarily restores the interrupt to _level before immediately

 *  disabling them again.  This is used to divide long RTEMS critical

 *  sections into two or more parts.  The parameter _level is not

 * modified.

 */

#define _CPU_ISR_Flash( _level) \

  sh_flash_interrupts( _level)

/*

 *  Map interrupt level in task mode onto the hardware that the CPU

 *  actually provides.  Currently, interrupt levels which do not

 *  map onto the CPU in a generic fashion are undefined.  Someday,

 *  it would be nice if these were "mapped" by the application

 *  via a callout.  For example, m68k has 8 levels 0 - 7, levels

 *  8 - 255 would be available for bsp/application specific meaning.

 *  This could be used to manage a programmable interrupt controller

 *  via the rtems_task_mode directive.

 */

#define _CPU_ISR_Set_level( _newlevel) \

  sh_set_interrupt_level(_newlevel)

unsigned32 _CPU_ISR_Get_level( void );

/* end of ISR handler macros */

/* 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.

 *

 *  NOTE: This is_fp parameter is TRUE if the thread is to be a floating

 *        point thread.  This is typically only used on CPUs where the

 *        FPU may be easily disabled by software such as on the SPARC

 *        where the PSR contains an enable FPU bit.

 */

/*

 * FIXME: defined as a function for debugging - should be a macro

 */

SCORE_EXTERN void _CPU_Context_Initialize(

  Context_Control       *_the_context,

  void                  *_stack_base,

  unsigned32            _size,

  unsigned32            _isr,

  void    (*_entry_point)(void),

  int                   _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.

 *  SH1, SH2, SH3 have no FPU, but the SH3e and SH4 have.

 */

#define _CPU_Context_Initialize_fp( _destination ) \

  {  }

/* end of Context handler macros */

/* Fatal Error manager macros */

/*

 * FIXME: Trap32 ???

 *

 *  This routine copies _error into a known place -- typically a stack

 *  location or a register, optionally disables interrupts, and

 *  invokes a Trap32 Instruction which returns to the breakpoint

 *  routine of cmon.

 */

#ifdef BSP_FATAL_HALT

  /* we manage the fatal error in the board support package */

  void bsp_fatal_halt( unsigned32 _error);

#define _CPU_Fatal_halt( _error ) bsp_fatal_halt( _error)

#else

#define _CPU_Fatal_halt( _error)\

{ \

  asm volatile("mov.l %0,r0"::"m" (_error)); \

  asm volatile("trapa #34"); \

}

#endif

/* end of Fatal Error manager macros */

/* 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_USE_GENERIC_BITFIELD_CODE TRUE

#define CPU_USE_GENERIC_BITFIELD_DATA TRUE

#if (CPU_USE_GENERIC_BITFIELD_CODE == FALSE)

extern unsigned8 _bit_set_table[];

#define _CPU_Bitfield_Find_first_bit( _value, _output ) \

  { \

      _output = 0;\

      if(_value > 0x00ff) \

      { _value >>= 8; _output = 8; } \

      if(_value > 0x000f) \

        { _output += 4; _value >>= 4; } \

      _output += _bit_set_table[ _value]; }

#endif

/* 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.

 */

#if (CPU_USE_GENERIC_BITFIELD_CODE == FALSE)

#define _CPU_Priority_Mask( _bit_number ) \

  ( 1 << (_bit_number) )

#endif

/*

 *  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.

 */

#if (CPU_USE_GENERIC_BITFIELD_CODE == FALSE)

#define _CPU_Priority_bits_index( _priority ) \

  (_priority)

#endif

/* end of Priority handler macros */

/* functions */

/*

 *  _CPU_Initialize

 *

 *  This routine performs CPU dependent initialization.

 */

void _CPU_Initialize(

  rtems_cpu_table  *cpu_table,

  void      (*thread_dispatch)

);

/*

 *  _CPU_ISR_install_raw_handler

 *

 *  This routine installs a "raw" interrupt handler directly into the

 *  processor's vector table.

 */

void _CPU_ISR_install_raw_handler(

  unsigned32  vector,

  proc_ptr    new_handler,

  proc_ptr   *old_handler

);

/*

 *  _CPU_ISR_install_vector

 *

 *  This routine installs an interrupt vector.

 */

void _CPU_ISR_install_vector(

  unsigned32  vector,

  proc_ptr    new_handler,

  proc_ptr   *old_handler

);

/*

 *  _CPU_Install_interrupt_stack

 *

 *  This routine installs the hardware interrupt stack pointer.

 *

 *  NOTE:  It needs only be provided if CPU_HAS_HARDWARE_INTERRUPT_STACK

 *         is TRUE.

 */

void _CPU_Install_interrupt_stack( void );

/*

 *  _CPU_Thread_Idle_body

 *

 *  This routine is the CPU dependent IDLE thread body.

 *

 *  NOTE:  It need only be provided if CPU_PROVIDES_IDLE_THREAD_BODY

 *         is TRUE.

 */

void _CPU_Thread_Idle_body( 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 generally used only to restart self in an

 *  efficient manner.  It may simply be a label in _CPU_Context_switch.

 */

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

);

/*