/* cpu_asm.s
*
* This file contains the basic algorithms for all assembly code used
* in an specific CPU port of RTEMS. These algorithms must be implemented
* in assembly language.
*
* COPYRIGHT (c) 1989-2011.
* On-Line Applications Research Corporation (OAR).
*
* Copyright (c) 2014 embedded brains GmbH
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
*
* Ported to ERC32 implementation of the SPARC by On-Line Applications
* Research Corporation (OAR) under contract to the European Space
* Agency (ESA).
*
* ERC32 modifications of respective RTEMS file: COPYRIGHT (c) 1995.
* European Space Agency.
*/
#include <rtems/asm.h>
#include <rtems/score/percpu.h>
#include <bspopts.h>
/*
* void _CPU_Context_switch(
* Context_Control *run,
* Context_Control *heir
* )
*
* This routine performs a normal non-FP context switch.
*/
.align 4
PUBLIC(_CPU_Context_switch)
SYM(_CPU_Context_switch):
st %g5, [%o0 + G5_OFFSET] ! save the global registers
st %g7, [%o0 + G7_OFFSET]
std %l0, [%o0 + L0_OFFSET] ! save the local registers
std %l2, [%o0 + L2_OFFSET]
std %l4, [%o0 + L4_OFFSET]
std %l6, [%o0 + L6_OFFSET]
std %i0, [%o0 + I0_OFFSET] ! save the input registers
std %i2, [%o0 + I2_OFFSET]
std %i4, [%o0 + I4_OFFSET]
std %i6, [%o0 + I6_FP_OFFSET]
std %o6, [%o0 + O6_SP_OFFSET] ! save the output registers
! load the ISR stack nesting prevention flag
ld [%g6 + SPARC_PER_CPU_ISR_DISPATCH_DISABLE], %o4
! save it a bit later so we do not waste a couple of cycles
rd %psr, %o2
st %o2, [%o0 + PSR_OFFSET] ! save status register
! Now actually save ISR stack nesting prevention flag
st %o4, [%o0 + ISR_DISPATCH_DISABLE_STACK_OFFSET]
/*
* This is entered from _CPU_Context_restore with:
* o1 = context to restore
* o2 = psr
*/
PUBLIC(_CPU_Context_restore_heir)
SYM(_CPU_Context_restore_heir):
/*
* Flush all windows with valid contents except the current one.
* In examining the set register windows, one may logically divide
* the windows into sets (some of which may be empty) based on their
* current status:
*
* + current (i.e. in use),
* + used (i.e. a restore would not trap)
* + invalid (i.e. 1 in corresponding bit in WIM)
* + unused
*
* Either the used or unused set of windows may be empty.
*
* NOTE: We assume only one bit is set in the WIM at a time.
*
* Given a CWP of 5 and a WIM of 0x1, the registers are divided
* into sets as follows:
*
* + 0 - invalid
* + 1-4 - unused
* + 5 - current
* + 6-7 - used
*
* In this case, we only would save the used windows -- 6 and 7.
*
* Traps are disabled for the same logical period as in a
* flush all windows trap handler.
*
* Register Usage while saving the windows:
* g1 = current PSR
* g2 = current wim
* g3 = CWP
* g4 = wim scratch
* g5 = scratch
*/
ld [%o1 + PSR_OFFSET], %g1 ! g1 = saved psr
and %o2, SPARC_PSR_CWP_MASK, %g3 ! g3 = CWP
! g1 = psr w/o cwp
andn %g1, SPARC_PSR_ET_MASK | SPARC_PSR_CWP_MASK, %g1
or %g1, %g3, %g1 ! g1 = heirs psr
mov %g1, %psr ! restore status register and
! **** DISABLE TRAPS ****
mov %wim, %g2 ! g2 = wim
mov 1, %g4
sll %g4, %g3, %g4 ! g4 = WIM mask for CW invalid
save_frame_loop:
sll %g4, 1, %g5 ! rotate the "wim" left 1
srl %g4, SPARC_NUMBER_OF_REGISTER_WINDOWS - 1, %g4
or %g4, %g5, %g4 ! g4 = wim if we do one restore
/*
* If a restore would not underflow, then continue.
*/
andcc %g4, %g2, %g0 ! Any windows to flush?
bnz done_flushing ! No, then continue
nop
restore ! back one window
/*
* Now save the window just as if we overflowed to it.
*/
std %l0, [%sp + CPU_STACK_FRAME_L0_OFFSET]
std %l2, [%sp + CPU_STACK_FRAME_L2_OFFSET]
std %l4, [%sp + CPU_STACK_FRAME_L4_OFFSET]
std %l6, [%sp + CPU_STACK_FRAME_L6_OFFSET]
std %i0, [%sp + CPU_STACK_FRAME_I0_OFFSET]
std %i2, [%sp + CPU_STACK_FRAME_I2_OFFSET]
std %i4, [%sp + CPU_STACK_FRAME_I4_OFFSET]
std %i6, [%sp + CPU_STACK_FRAME_I6_FP_OFFSET]
ba save_frame_loop
nop
done_flushing:
add %g3, 1, %g3 ! calculate desired WIM
and %g3, SPARC_NUMBER_OF_REGISTER_WINDOWS - 1, %g3
mov 1, %g4
sll %g4, %g3, %g4 ! g4 = new WIM
mov %g4, %wim
or %g1, SPARC_PSR_ET_MASK, %g1
mov %g1, %psr ! **** ENABLE TRAPS ****
! and restore CWP
nop
nop
nop
#if defined(RTEMS_SMP)
! The executing context no longer executes on this processor
st %g0, [%o0 + SPARC_CONTEXT_CONTROL_IS_EXECUTING_OFFSET]
! Try to update the is executing indicator of the heir context
mov 1, %g1
try_update_is_executing:
swap [%o1 + SPARC_CONTEXT_CONTROL_IS_EXECUTING_OFFSET], %g1
cmp %g1, 0
bne check_is_executing
! The next load is in a delay slot, which is all right
#endif
ld [%o1 + G5_OFFSET], %g5 ! restore the global registers
ld [%o1 + G7_OFFSET], %g7
! Load thread specific ISR dispatch prevention flag
ld [%o1 + ISR_DISPATCH_DISABLE_STACK_OFFSET], %o2
! Store it to memory later to use the cycles
ldd [%o1 + L0_OFFSET], %l0 ! restore the local registers
ldd [%o1 + L2_OFFSET], %l2
ldd [%o1 + L4_OFFSET], %l4
ldd [%o1 + L6_OFFSET], %l6
! Now restore thread specific ISR dispatch prevention flag
st %o2, [%g6 + SPARC_PER_CPU_ISR_DISPATCH_DISABLE]
ldd [%o1 + I0_OFFSET], %i0 ! restore the input registers
ldd [%o1 + I2_OFFSET], %i2
ldd [%o1 + I4_OFFSET], %i4
ldd [%o1 + I6_FP_OFFSET], %i6
ldd [%o1 + O6_SP_OFFSET], %o6 ! restore the output registers
jmp %o7 + 8 ! return
nop ! delay slot
#if defined(RTEMS_SMP)
check_is_executing:
! Check the is executing indicator of the heir context
ld [%o1 + SPARC_CONTEXT_CONTROL_IS_EXECUTING_OFFSET], %g1
cmp %g1, 0
beq try_update_is_executing
mov 1, %g1
! Check if a thread dispatch is necessary
ldub [%g6 + PER_CPU_DISPATCH_NEEDED], %g1
cmp %g1, 0
beq check_is_executing
nop
! We have a new heir
! Clear the thread dispatch necessary flag
stub %g0, [%g6 + PER_CPU_DISPATCH_NEEDED]
! Here we assume a strong memory order, otherwise a memory barrier must
! be inserted here
! Read the executing and heir
ld [%g6 + PER_CPU_OFFSET_EXECUTING], %g1
ld [%g6 + PER_CPU_OFFSET_HEIR], %g2
! Calculate the heir context pointer
sub %o1, %g1, %g1
add %g1, %g2, %o1
! Update the executing
st %g2, [%g6 + PER_CPU_OFFSET_EXECUTING]
ba try_update_is_executing
mov 1, %g1
#endif
/*
* void _CPU_Context_restore(
* Context_Control *new_context
* )
*
* This routine is generally used only to perform restart self.
*
* NOTE: It is unnecessary to reload some registers.
*/
.align 4
PUBLIC(_CPU_Context_restore)
SYM(_CPU_Context_restore):
save %sp, -CPU_MINIMUM_STACK_FRAME_SIZE, %sp
rd %psr, %o2
#if defined(RTEMS_SMP)
! On SPARC the restore path needs also a valid executing context on SMP
! to update the is executing indicator.
mov %i0, %o0
#endif
ba SYM(_CPU_Context_restore_heir)
mov %i0, %o1 ! in the delay slot
/*
* void _ISR_Handler()
*
* This routine provides the RTEMS interrupt management.
*
* We enter this handler from the 4 instructions in the trap table with
* the following registers assumed to be set as shown:
*
* l0 = PSR
* l1 = PC
* l2 = nPC
* l3 = trap type
*
* NOTE: By an executive defined convention, trap type is between 0 and 255 if
* it is an asynchonous trap and 256 and 511 if it is synchronous.
*/
.align 4
PUBLIC(_ISR_Handler)
SYM(_ISR_Handler):
/*
* Fix the return address for synchronous traps.
*/
andcc %l3, SPARC_SYNCHRONOUS_TRAP_BIT_MASK, %g0
! Is this a synchronous trap?
be,a win_ovflow ! No, then skip the adjustment
nop ! DELAY
mov %l1, %l6 ! save trapped pc for debug info
mov %l2, %l1 ! do not return to the instruction
add %l2, 4, %l2 ! indicated
win_ovflow:
/*
* Save the globals this block uses.
*
* These registers are not restored from the locals. Their contents
* are saved directly from the locals into the ISF below.
*/
mov %g4, %l4 ! save the globals this block uses
mov %g5, %l5
/*
* When at a "window overflow" trap, (wim == (1 << cwp)).
* If we get here like that, then process a window overflow.
*/
rd %wim, %g4
srl %g4, %l0, %g5 ! g5 = win >> cwp ; shift count and CWP
! are LS 5 bits ; how convenient :)
cmp %g5, 1 ! Is this an invalid window?
bne dont_do_the_window ! No, then skip all this stuff
! we are using the delay slot
/*
* The following is same as a 1 position right rotate of WIM
*/
srl %g4, 1, %g5 ! g5 = WIM >> 1
sll %g4, SPARC_NUMBER_OF_REGISTER_WINDOWS-1 , %g4
! g4 = WIM << (Number Windows - 1)
or %g4, %g5, %g4 ! g4 = (WIM >> 1) |
! (WIM << (Number Windows - 1))
/*
* At this point:
*
* g4 = the new WIM
* g5 is free
*/
/*
* Since we are tinkering with the register windows, we need to
* make sure that all the required information is in global registers.
*/
save ! Save into the window
wr %g4, 0, %wim ! WIM = new WIM
nop ! delay slots
nop
nop
/*
* Now save the window just as if we overflowed to it.
*/
std %l0, [%sp + CPU_STACK_FRAME_L0_OFFSET]
std %l2, [%sp + CPU_STACK_FRAME_L2_OFFSET]
std %l4, [%sp + CPU_STACK_FRAME_L4_OFFSET]
std %l6, [%sp + CPU_STACK_FRAME_L6_OFFSET]
std %i0, [%sp + CPU_STACK_FRAME_I0_OFFSET]
std %i2, [%sp + CPU_STACK_FRAME_I2_OFFSET]
std %i4, [%sp + CPU_STACK_FRAME_I4_OFFSET]
std %i6, [%sp + CPU_STACK_FRAME_I6_FP_OFFSET]
restore
nop
dont_do_the_window:
/*
* Global registers %g4 and %g5 are saved directly from %l4 and
* %l5 directly into the ISF below.
*/
save_isf:
/*
* Save the state of the interrupted task -- especially the global
* registers -- in the Interrupt Stack Frame. Note that the ISF
* includes a regular minimum stack frame which will be used if
* needed by register window overflow and underflow handlers.
*
* REGISTERS SAME AS AT _ISR_Handler
*/
sub %fp, CONTEXT_CONTROL_INTERRUPT_FRAME_SIZE, %sp
! make space for ISF
std %l0, [%sp + ISF_PSR_OFFSET] ! save psr, PC
st %l2, [%sp + ISF_NPC_OFFSET] ! save nPC
st %g1, [%sp + ISF_G1_OFFSET] ! save g1
std %g2, [%sp + ISF_G2_OFFSET] ! save g2, g3
std %l4, [%sp + ISF_G4_OFFSET] ! save g4, g5 -- see above
st %g7, [%sp + ISF_G7_OFFSET] ! save g7
std %i0, [%sp + ISF_I0_OFFSET] ! save i0, i1
std %i2, [%sp + ISF_I2_OFFSET] ! save i2, i3
std %i4, [%sp + ISF_I4_OFFSET] ! save i4, i5
std %i6, [%sp + ISF_I6_FP_OFFSET] ! save i6/fp, i7
rd %y, %g1
st %g1, [%sp + ISF_Y_OFFSET] ! save y
st %l6, [%sp + ISF_TPC_OFFSET] ! save real trapped pc
mov %sp, %o1 ! 2nd arg to ISR Handler
/*
* Increment ISR nest level and Thread dispatch disable level.
*
* Register usage for this section:
*
* l6 = _Thread_Dispatch_disable_level value
* l7 = _ISR_Nest_level value
*
* NOTE: It is assumed that l6 - l7 will be preserved until the ISR
* nest and thread dispatch disable levels are unnested.
*/
ld [%g6 + PER_CPU_ISR_NEST_LEVEL], %l7
ld [%g6 + PER_CPU_THREAD_DISPATCH_DISABLE_LEVEL], %l6
add %l7, 1, %l7
st %l7, [%g6 + PER_CPU_ISR_NEST_LEVEL]
add %l6, 1, %l6
st %l6, [%g6 + PER_CPU_THREAD_DISPATCH_DISABLE_LEVEL]
/*
* If ISR nest level was zero (now 1), then switch stack.
*/
mov %sp, %fp
subcc %l7, 1, %l7 ! outermost interrupt handler?
bnz dont_switch_stacks ! No, then do not switch stacks
#if defined( RTEMS_PROFILING )
sethi %hi(SYM(_SPARC_Counter)), %o5
ld [%o5 + %lo(SYM(_SPARC_Counter))], %l4
ld [%l4], %o5
#else
nop
#endif
ld [%g6 + PER_CPU_INTERRUPT_STACK_HIGH], %sp
dont_switch_stacks:
/*
* Make sure we have a place on the stack for the window overflow
* trap handler to write into. At this point it is safe to
* enable traps again.
*/
sub %sp, CPU_MINIMUM_STACK_FRAME_SIZE, %sp
/*
* Check if we have an external interrupt (trap 0x11 - 0x1f). If so,
* set the PIL in the %psr to mask off interrupts with lower priority.
* The original %psr in %l0 is not modified since it will be restored
* when the interrupt handler returns.
*/
mov %l0, %g5
and %l3, 0x0ff, %g4
subcc %g4, 0x11, %g0
bl dont_fix_pil
subcc %g4, 0x1f, %g0
bg dont_fix_pil
sll %g4, 8, %g4
and %g4, SPARC_PSR_PIL_MASK, %g4
andn %l0, SPARC_PSR_PIL_MASK, %g5
ba pil_fixed
or %g4, %g5, %g5
dont_fix_pil:
or %g5, SPARC_PSR_PIL_MASK, %g5
pil_fixed:
wr %g5, SPARC_PSR_ET_MASK, %psr ! **** ENABLE TRAPS ****
dont_fix_pil2:
/*
* Vector to user's handler.
*
* NOTE: TBR may no longer have vector number in it since
* we just enabled traps. It is definitely in l3.
*/
sethi %hi(SYM(_ISR_Vector_table)), %g4
or %g4, %lo(SYM(_ISR_Vector_table)), %g4
and %l3, 0xFF, %g5 ! remove synchronous trap indicator
sll %g5, 2, %g5 ! g5 = offset into table
ld [%g4 + %g5], %g4 ! g4 = _ISR_Vector_table[ vector ]
! o1 = 2nd arg = address of the ISF
! WAS LOADED WHEN ISF WAS SAVED!!!
mov %l3, %o0 ! o0 = 1st arg = vector number
call %g4, 0
#if defined( RTEMS_PROFILING )
mov %o5, %l3 ! save interrupt entry instant
cmp %l7, 0
bne profiling_not_outer_most_exit
nop
ta SPARC_SWTRAP_IRQDIS ! Call interrupt disable trap handler
ld [%l4], %o2 ! o2 = 3rd arg = interrupt exit instant
mov %l3, %o1 ! o1 = 2nd arg = interrupt entry instant
call SYM(_Profiling_Outer_most_interrupt_entry_and_exit), 0
mov %g6, %o0 ! o0 = 1st arg = per-CPU control
profiling_not_outer_most_exit:
#else
nop ! delay slot
#endif
/*
* Redisable traps so we can finish up the interrupt processing.
* This is a VERY conservative place to do this.
*
* NOTE: %l0 has the PSR which was in place when we took the trap.
*/
mov %l0, %psr ! **** DISABLE TRAPS ****
nop; nop; nop
/*
* Decrement ISR nest level and Thread dispatch disable level.
*
* Register usage for this section:
*
* l6 = _Thread_Dispatch_disable_level value
* l7 = _ISR_Nest_level value
*/
st %l7, [%g6 + PER_CPU_ISR_NEST_LEVEL]
sub %l6, 1, %l6
st %l6, [%g6 + PER_CPU_THREAD_DISPATCH_DISABLE_LEVEL]
/*
* If dispatching is disabled (includes nested interrupt case),
* then do a "simple" exit.
*/
orcc %l6, %g0, %g0 ! Is dispatching disabled?
bnz simple_return ! Yes, then do a "simple" exit
nop
! Are we dispatching from a previous ISR in the interrupted thread?
ld [%g6 + SPARC_PER_CPU_ISR_DISPATCH_DISABLE], %l7
orcc %l7, %g0, %g0 ! Is this thread already doing an ISR?
bnz simple_return ! Yes, then do a "simple" exit
nop
/*
* If a context switch is necessary, then do fudge stack to
* return to the interrupt dispatcher.
*/
ldub [%g6 + PER_CPU_DISPATCH_NEEDED], %l6
orcc %l6, %g0, %g0 ! Is thread switch necessary?
bz simple_return ! no, then do a simple return
nop
/*
* Invoke interrupt dispatcher.
*/
! Set ISR dispatch nesting prevention flag
mov 1,%l6
st %l6, [%g6 + SPARC_PER_CPU_ISR_DISPATCH_DISABLE]
/*
* The following subtract should get us back on the interrupted
* tasks stack and add enough room to invoke the dispatcher.
* When we enable traps, we are mostly back in the context
* of the task and subsequent interrupts can operate normally.
*/
sub %fp, CPU_MINIMUM_STACK_FRAME_SIZE, %sp
or %l0, SPARC_PSR_ET_MASK, %l7 ! l7 = PSR with ET=1
mov %l7, %psr ! **** ENABLE TRAPS ****
nop
nop
nop
isr_dispatch:
call SYM(_Thread_Dispatch), 0
nop
/*
* We invoked _Thread_Dispatch in a state similar to the interrupted
* task. In order to safely be able to tinker with the register
* windows and get the task back to its pre-interrupt state,
* we need to disable interrupts disabled so we can safely tinker
* with the register windowing. In particular, the CWP in the PSR
* is fragile during this period. (See PR578.)
*/
ta SPARC_SWTRAP_IRQDIS ! syscall (disable interrupts)
/*
* While we had ISR dispatching disabled in this thread,
* did we miss anything. If so, then we need to do another
* _Thread_Dispatch before leaving this ISR Dispatch context.
*/
ldub [%g6 + PER_CPU_DISPATCH_NEEDED], %l7
orcc %l7, %g0, %g0 ! Is thread switch necesary?
bne,a isr_dispatch ! Yes, then invoke the dispatcher.
! g1 = Old PSR PIL returned from IRQDis
ta SPARC_SWTRAP_IRQEN ! syscall (enable interrupts to same level)
! No, then clear out and return
allow_nest_again:
! Zero out ISR stack nesting prevention flag
st %g0, [%g6 + SPARC_PER_CPU_ISR_DISPATCH_DISABLE]
/*
* The CWP in place at this point may be different from
* that which was in effect at the beginning of the ISR if we
* have been context switched between the beginning of this invocation
* of _ISR_Handler and this point. Thus the CWP and WIM should
* not be changed back to their values at ISR entry time. Any
* changes to the PSR must preserve the CWP.
*/
simple_return:
ld [%fp + ISF_Y_OFFSET], %l5 ! restore y
wr %l5, 0, %y
ldd [%fp + ISF_PSR_OFFSET], %l0 ! restore psr, PC
ld [%fp + ISF_NPC_OFFSET], %l2 ! restore nPC
rd %psr, %l3
and %l3, SPARC_PSR_CWP_MASK, %l3 ! want "current" CWP
andn %l0, SPARC_PSR_CWP_MASK, %l0 ! want rest from task
or %l3, %l0, %l0 ! install it later...
andn %l0, SPARC_PSR_ET_MASK, %l0
/*
* Restore tasks global and out registers
*/
mov %fp, %g1
! g1 is restored later
ldd [%fp + ISF_G2_OFFSET], %g2 ! restore g2, g3
ldd [%fp + ISF_G4_OFFSET], %g4 ! restore g4, g5
ld [%fp + ISF_G7_OFFSET], %g7 ! restore g7
ldd [%fp + ISF_I0_OFFSET], %i0 ! restore i0, i1
ldd [%fp + ISF_I2_OFFSET], %i2 ! restore i2, i3
ldd [%fp + ISF_I4_OFFSET], %i4 ! restore i4, i5
ldd [%fp + ISF_I6_FP_OFFSET], %i6 ! restore i6/fp, i7
/*
* Registers:
*
* ALL global registers EXCEPT G1 and the input registers have
* already been restored and thuse off limits.
*
* The following is the contents of the local registers:
*
* l0 = original psr
* l1 = return address (i.e. PC)
* l2 = nPC
* l3 = CWP
*/
/*
* if (CWP + 1) is an invalid window then we need to reload it.
*
* WARNING: Traps should now be disabled
*/
mov %l0, %psr ! **** DISABLE TRAPS ****
nop
nop
nop
rd %wim, %l4
add %l0, 1, %l6 ! l6 = cwp + 1
and %l6, SPARC_PSR_CWP_MASK, %l6 ! do the modulo on it
srl %l4, %l6, %l5 ! l5 = win >> cwp + 1 ; shift count
! and CWP are conveniently LS 5 bits
cmp %l5, 1 ! Is tasks window invalid?
bne good_task_window
/*
* The following code is the same as a 1 position left rotate of WIM.
*/
sll %l4, 1, %l5 ! l5 = WIM << 1
srl %l4, SPARC_NUMBER_OF_REGISTER_WINDOWS-1 , %l4
! l4 = WIM >> (Number Windows - 1)
or %l4, %l5, %l4 ! l4 = (WIM << 1) |
! (WIM >> (Number Windows - 1))
/*
* Now restore the window just as if we underflowed to it.
*/
wr %l4, 0, %wim ! WIM = new WIM
nop ! must delay after writing WIM
nop
nop
restore ! now into the tasks window
ldd [%g1 + CPU_STACK_FRAME_L0_OFFSET], %l0
ldd [%g1 + CPU_STACK_FRAME_L2_OFFSET], %l2
ldd [%g1 + CPU_STACK_FRAME_L4_OFFSET], %l4
ldd [%g1 + CPU_STACK_FRAME_L6_OFFSET], %l6
ldd [%g1 + CPU_STACK_FRAME_I0_OFFSET], %i0
ldd [%g1 + CPU_STACK_FRAME_I2_OFFSET], %i2
ldd [%g1 + CPU_STACK_FRAME_I4_OFFSET], %i4
ldd [%g1 + CPU_STACK_FRAME_I6_FP_OFFSET], %i6
! reload of sp clobbers ISF
save ! Back to ISR dispatch window
good_task_window:
mov %l0, %psr ! **** DISABLE TRAPS ****
nop; nop; nop
! and restore condition codes.
ld [%g1 + ISF_G1_OFFSET], %g1 ! restore g1
jmp %l1 ! transfer control and
rett %l2 ! go back to tasks window
/* end of file */