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2001-08-09 Chris Johns <ccj@acm.org>

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* cpu_asm.S: This patch was co-developed with Eric Norum
	<eric.norum@usask.ca>.  It closes a one instruction window
	on some m68k CPU cores.  It fixes symptoms seen as:
	    1) No more `interrupt handler invoked twice for
	       a single interrupt'.
	    2) No more `lockup when mc68360 CPM and PIT interrupts
	       are at different levels'.
	It does insert a little more overhead on machines without hardware
	interrupt stacks but correctness has a price.
This commit is contained in:
Joel Sherrill
2001-08-09 21:09:52 +00:00
parent 3bb9542cd6
commit 256226b87e
1 changed files with 37 additions and 64 deletions
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101
c/src/exec/score/cpu/m68k/cpu_asm.S
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@@ -3,7 +3,7 @@
* This file contains all assembly code for the MC68020 implementation * This file contains all assembly code for the MC68020 implementation
* of RTEMS. * of RTEMS.
* *
* COPYRIGHT (c) 1989-1999. * COPYRIGHT (c) 1989-2001.
* On-Line Applications Research Corporation (OAR). * On-Line Applications Research Corporation (OAR).
* *
* The license and distribution terms for this file may be * The license and distribution terms for this file may be
@@ -68,7 +68,7 @@ SYM (_CPU_Context_save_fp):
moval a1@,a0 | a0 = Save context area moval a1@,a0 | a0 = Save context area
fsave a0@- | save 68881/68882 state frame fsave a0@- | save 68881/68882 state frame
tstb a0@ | check for a null frame tstb a0@ | check for a null frame
beq nosv | Yes, skip save of user model beq.b nosv | Yes, skip save of user model
fmovem fp0-fp7,a0@- | save data registers (fp0-fp7) fmovem fp0-fp7,a0@- | save data registers (fp0-fp7)
fmovem fpc/fps/fpi,a0@- | and save control registers fmovem fpc/fps/fpi,a0@- | and save control registers
movl #-1,a0@- | place not-null flag on stack movl #-1,a0@- | place not-null flag on stack
@@ -83,7 +83,7 @@ SYM (_CPU_Context_restore_fp):
moval a7@(FPCONTEXT_ARG),a1 | a1 = &ptr to context area moval a7@(FPCONTEXT_ARG),a1 | a1 = &ptr to context area
moval a1@,a0 | a0 = address of saved context moval a1@,a0 | a0 = address of saved context
tstb a0@ | Null context frame? tstb a0@ | Null context frame?
beq norst | Yes, skip fp restore beq.b norst | Yes, skip fp restore
addql #4,a0 | throwaway non-null flag addql #4,a0 | throwaway non-null flag
fmovem a0@+,fpc/fps/fpi | restore control registers fmovem a0@+,fpc/fps/fpi | restore control registers
fmovem a0@+,fp0-fp7 | restore data regs (fp0-fp7) fmovem a0@+,fp0-fp7 | restore data regs (fp0-fp7)
@@ -101,24 +101,12 @@ norst: frestore a0@+ | restore the fp state frame
* NOTE: * NOTE:
* Upon entry, the master stack will contain an interrupt stack frame * Upon entry, the master stack will contain an interrupt stack frame
* back to the interrupted thread and the interrupt stack will contain * back to the interrupted thread and the interrupt stack will contain
* a throwaway interrupt stack frame. If dispatching is enabled, this * a throwaway interrupt stack frame. If dispatching is enabled, and this
* is the outer most interrupt, and (a context switch is necessary or * is the outer most interrupt, and a context switch is necessary or
* the current thread has signals), then set up the master stack to * the current thread has pending signals, then set up the master stack to
* transfer control to the interrupt dispatcher. * transfer control to the interrupt dispatcher.
*/ */
/*
* With this approach, lower priority interrupts may
* execute twice if a higher priority interrupt is
* acknowledged before _Thread_Dispatch_disable is
* incremented and the higher priority interrupt
* performs a context switch after executing. The lower
* priority interrupt will execute (1) at the end of the
* higher priority interrupt in the new context if
* permitted by the new interrupt level mask, and (2) when
* the original context regains the cpu.
*/
#if ( M68K_COLDFIRE_ARCH == 1 ) #if ( M68K_COLDFIRE_ARCH == 1 )
.set SR_OFFSET, 2 | Status register offset .set SR_OFFSET, 2 | Status register offset
.set PC_OFFSET, 4 | Program Counter offset .set PC_OFFSET, 4 | Program Counter offset
@@ -142,45 +130,31 @@ SYM (_ISR_Handler):
addql #1,SYM (_Thread_Dispatch_disable_level) | disable multitasking addql #1,SYM (_Thread_Dispatch_disable_level) | disable multitasking
#if ( M68K_COLDFIRE_ARCH == 0 ) #if ( M68K_COLDFIRE_ARCH == 0 )
moveml d0-d1/a0-a1,a7@- | save d0-d1,a0-a1 moveml d0-d1/a0-a1,a7@- | save d0-d1,a0-a1
movew a7@(SAVED+FVO_OFFSET),d0 | d0 = F/VO
andl #0x0fff,d0 | d0 = vector offset in vbr
#else #else
lea a7@(-SAVED),a7 lea a7@(-SAVED),a7
movm.l d0-d1/a0-a1,a7@ | save d0-d1,a0-a1 movm.l d0-d1/a0-a1,a7@ | save d0-d1,a0-a1
#endif
movew a7@(SAVED+FVO_OFFSET),d0 | d0 = F/VO movew a7@(SAVED+FVO_OFFSET),d0 | d0 = F/VO
andl #0x0ffc,d0 | d0 = vector offset in vbr andl #0x0ffc,d0 | d0 = vector offset in vbr
#endif
#if ( CPU_HAS_SOFTWARE_INTERRUPT_STACK == 1 ) #if ( CPU_HAS_SOFTWARE_INTERRUPT_STACK == 1 )
#if ( M68K_COLDFIRE_ARCH == 0 ) movel _CPU_Interrupt_stack_high,a0 | a0 now point just above interrupt stack
movew sr,d1 | Save status register cmpl _CPU_Interrupt_stack_low,a7 | stack below interrupt stack?
oriw #0x700,sr | Disable interrupts bcs.b 1f | yes, switch to interrupt stack
#else cmpl a0,a7 | stack above interrupt stack?
move.l d0,a7@- | Save d0 value bcs.b 2f | no, do not switch stacks
move.l #0x700,d0 | Load in disable ints value
move.w sr,d1 | Grab SR
or.l d1,d0 | Create new SR
move.w d0,sr | Disable interrupts
move.l a7@+,d0 | Restore d0 value
#endif
tstl SYM (_ISR_Nest_level) | Interrupting an interrupt handler?
bne 1f | Yes, just skip over stack switch code
movel SYM(_CPU_Interrupt_stack_high),a0 | End of interrupt stack
movel a7,a0@- | Save task stack pointer
movel a0,a7 | Switch to interrupt stack
1: 1:
addql #1,SYM(_ISR_Nest_level) | one nest level deeper movel a7,a1 | copy task stack pointer
movew d1,sr | Restore status register movel a0,a7 | switch to interrupt stack
#else movel a1,a7@- | store task stack pointer on interrupt stack
addql #1,SYM (_ISR_Nest_level) | one nest level deeper 2:
#endif /* CPU_HAS_SOFTWARE_INTERRUPT_STACK == 1 */ #endif /* CPU_HAS_SOFTWARE_INTERRUPT_STACK == 1 */
#if ( M68K_HAS_PREINDEXING == 1 ) #if ( M68K_HAS_PREINDEXING == 1 )
movel @( SYM (_ISR_Vector_table),d0:w:1),a0| fetch the ISR movel @( SYM (_ISR_Vector_table),d0:w:1),a0| fetch the ISR
#else #else
movel # SYM (_ISR_Vector_table),a0 | a0 = base of RTEMS table movel # SYM (_ISR_Vector_table),a0 | a0 = base of RTEMS table
addal d0,a0 | a0 = address of vector addal d0,a0 | a0 = address of vector
movel (a0),a0 | a0 = address of user routine movel (a0),a0 | a0 = address of user routine
#endif #endif
@@ -191,45 +165,44 @@ SYM (_ISR_Handler):
addql #4,a7 | remove vector number addql #4,a7 | remove vector number
#if ( CPU_HAS_SOFTWARE_INTERRUPT_STACK == 1 ) #if ( CPU_HAS_SOFTWARE_INTERRUPT_STACK == 1 )
#if ( M68K_COLDFIRE_ARCH == 0 ) movel _CPU_Interrupt_stack_high,a0
movew sr,d0 | Save status register subql #4,a0
oriw #0x700,sr | Disable interrupts cmpl a0,a7 | At top of interrupt stack?
#else bne.b 1f | No, do not restore task stack pointer
move.l #0x700,d1 | Load in disable int value
move.w sr,d0 | Grab SR
or.l d0,d1 | Create new SR
move.w d1,sr | Load to disable interrupts
#endif
subql #1,SYM(_ISR_Nest_level) | Reduce interrupt-nesting count
bne 1f | Skip if return to interrupt
movel (a7),a7 | Restore task stack pointer movel (a7),a7 | Restore task stack pointer
1: 1:
movew d0,sr | Restore status register
#else
subql #1,SYM (_ISR_Nest_level) | one less nest level
#endif /* CPU_HAS_SOFTWARE_INTERRUPT_STACK == 1 */ #endif /* CPU_HAS_SOFTWARE_INTERRUPT_STACK == 1 */
subql #1,SYM (_Thread_Dispatch_disable_level) subql #1,SYM (_Thread_Dispatch_disable_level)
| unnest multitasking | unnest multitasking
bne exit | If dispatch disabled, exit bne.b exit | If dispatch disabled, exit
#if ( M68K_HAS_SEPARATE_STACKS == 1 ) #if ( M68K_HAS_SEPARATE_STACKS == 1 )
movew #0xf000,d0 | isolate format nibble movew #0xf000,d0 | isolate format nibble
andw a7@(SAVED+FVO_OFFSET),d0 | get F/VO andw a7@(SAVED+FVO_OFFSET),d0 | get F/VO
cmpiw #0x1000,d0 | is it a throwaway isf? cmpiw #0x1000,d0 | is it a throwaway isf?
bne exit | NOT outer level, so branch bne.b exit | NOT outer level, so branch
#else
/*
* If we have a CPU which allows a higher-priority interrupt to preempt a
* lower priority handler before the lower-priority handler can increment
* _Thread_Dispatch_disable_level then we must check the PC on the stack to
* see if it is _ISR_Handler. If it is we have the case of nesting interrupts
* without the dispatch level being incremented.
*/
#if ( M68K_COLDFIRE_ARCH == 0 && M68K_MC68060_ARCH == 0 )
cmpl #_ISR_Handler,a7@(SAVED+PC_OFFSET)
beq.b exit
#endif
#endif #endif
tstl SYM (_Context_Switch_necessary) tstl SYM (_Context_Switch_necessary)
| Is thread switch necessary? | Is thread switch necessary?
bne bframe | Yes, invoke dispatcher bne.b bframe | Yes, invoke dispatcher
tstl SYM (_ISR_Signals_to_thread_executing) tstl SYM (_ISR_Signals_to_thread_executing)
| signals sent to Run_thread | signals sent to Run_thread
| while in interrupt handler? | while in interrupt handler?
beq exit | No, then exit beq.b exit | No, then exit
bframe: clrl SYM (_ISR_Signals_to_thread_executing) bframe: clrl SYM (_ISR_Signals_to_thread_executing)
| If sent, will be processed | If sent, will be processed