/*******************************************************************************
Copyright (c) 2006-2009 by Tensilica Inc. ALL RIGHTS RESERVED.
These coded instructions, statements, and computer programs are the
copyrighted works and confidential proprietary information of Tensilica Inc.
They may not be modified, copied, reproduced, distributed, or disclosed to
third parties in any manner, medium, or form, in whole or in part, without
the prior written consent of Tensilica Inc.
--------------------------------------------------------------------------------
XTENSA CONTEXT SAVE AND RESTORE ROUTINES
Low-level Call0 functions for handling generic context save and restore of
registers not specifically addressed by the interrupt vectors and handlers.
Those registers (not handled by these functions) are PC, PS, A0, A1 (SP).
Except for the calls to RTOS functions, this code is generic to Xtensa.
Note that in Call0 ABI, interrupt handlers are expected to preserve the callee-
save regs (A12-A15), which is always the case if the handlers are coded in C.
However A12, A13 are made available as scratch registers for interrupt dispatch
code, so are presumed saved anyway, and are always restored even in Call0 ABI.
Only A14, A15 are truly handled as callee-save regs.
Because Xtensa is a configurable architecture, this port supports all user
generated configurations (except restrictions stated in the release notes).
This is accomplished by conditional compilation using macros and functions
defined in the Xtensa HAL (hardware adaptation layer) for your configuration.
Only the processor state included in your configuration is saved and restored,
including any processor state added by user configuration options or TIE.
*******************************************************************************/
/* Warn nicely if this file gets named with a lowercase .s instead of .S: */
#define NOERROR #
NOERROR: .error "C preprocessor needed for this file: make sure its filename\
ends in uppercase .S, or use xt-xcc's -x assembler-with-cpp option."
#include "freertos/xtensa_rtos.h"
// .section .iram.text
.section .text
/*******************************************************************************
_xt_context_save
!! MUST BE CALLED ONLY BY 'CALL0' INSTRUCTION !!
Saves all Xtensa processor state except PC, PS, A0, A1 (SP), A12, A13, in the
interrupt stack frame defined in xtensa_rtos.h.
Its counterpart is _xt_context_restore (which also restores A12, A13).
Caller is expected to have saved PC, PS, A0, A1 (SP), A12, A13 in the frame.
This function preserves A12 & A13 in order to provide the caller with 2 scratch
regs that need not be saved over the call to this function. The choice of which
2 regs to provide is governed by xthal_window_spill_nw and xthal_save_extra_nw,
to avoid moving data more than necessary. Caller can assign regs accordingly.
Entry Conditions:
A0 = Return address in caller.
A1 = Stack pointer of interrupted thread or handler ("interruptee").
Original A12, A13 have already been saved in the interrupt stack frame.
Other processor state except PC, PS, A0, A1 (SP), A12, A13, is as at the
point of interruption.
If windowed ABI, PS.EXCM = 1 (exceptions disabled).
Exit conditions:
A0 = Return address in caller.
A1 = Stack pointer of interrupted thread or handler ("interruptee").
A12, A13 as at entry (preserved).
If windowed ABI, PS.EXCM = 1 (exceptions disabled).
*******************************************************************************/
.global _xt_context_save
.type _xt_context_save,@function
.align 4
_xt_context_save:
s32i a2, sp, XT_STK_A2
s32i a3, sp, XT_STK_A3
s32i a4, sp, XT_STK_A4
s32i a5, sp, XT_STK_A5
s32i a6, sp, XT_STK_A6
s32i a7, sp, XT_STK_A7
s32i a8, sp, XT_STK_A8
s32i a9, sp, XT_STK_A9
s32i a10, sp, XT_STK_A10
s32i a11, sp, XT_STK_A11
/*
Call0 ABI callee-saved regs a12-15 do not need to be saved here.
a12-13 are the caller's responsibility so it can use them as scratch.
So only need to save a14-a15 here for Windowed ABI (not Call0).
*/
#ifndef __XTENSA_CALL0_ABI__
s32i a14, sp, XT_STK_A14
s32i a15, sp, XT_STK_A15
#endif
rsr a3, SAR
s32i a3, sp, XT_STK_SAR
#if XCHAL_HAVE_LOOPS
rsr a3, LBEG
s32i a3, sp, XT_STK_LBEG
rsr a3, LEND
s32i a3, sp, XT_STK_LEND
rsr a3, LCOUNT
s32i a3, sp, XT_STK_LCOUNT
#endif
#if XCHAL_EXTRA_SA_SIZE > 0 || !defined(__XTENSA_CALL0_ABI__)
mov a9, a0 /* preserve ret addr */
#endif
#ifndef __XTENSA_CALL0_ABI__
/*
To spill the reg windows, temp. need pre-interrupt stack ptr and a4-15.
Need to save a9,12,13 temporarily (in frame temps) and recover originals.
Interrupts need to be disabled below XCHAL_EXCM_LEVEL and window overflow
and underflow exceptions disabled (assured by PS.EXCM == 1).
*/
s32i a12, sp, XT_STK_TMP+0 /* temp. save stuff in stack frame */
s32i a13, sp, XT_STK_TMP+4
s32i a9, sp, XT_STK_TMP+8
l32i a12, sp, XT_STK_A12 /* recover original a9,12,13 */
l32i a13, sp, XT_STK_A13
l32i a9, sp, XT_STK_A9
addi sp, sp, XT_STK_FRMSZ /* restore the interruptee's SP */
call0 xthal_window_spill_nw /* preserves only a4,5,8,9,12,13 */
addi sp, sp, -XT_STK_FRMSZ
l32i a12, sp, XT_STK_TMP+0 /* recover stuff from stack frame */
l32i a13, sp, XT_STK_TMP+4
l32i a9, sp, XT_STK_TMP+8
#endif
#if XCHAL_EXTRA_SA_SIZE > 0
/*
NOTE: Normally the xthal_save_extra_nw macro only affects address
registers a2-a5. It is theoretically possible for Xtensa processor
designers to write TIE that causes more address registers to be
affected, but it is generally unlikely. If that ever happens,
more registers need to be saved/restored around this macro invocation.
Here we assume a9,12,13 are preserved.
Future Xtensa tools releases might limit the regs that can be affected.
*/
addi a2, sp, XT_STK_EXTRA /* where to save it */
call0 xthal_save_extra_nw /* destroys a0,2,3,4,5 */
#endif
#if XCHAL_EXTRA_SA_SIZE > 0 || !defined(__XTENSA_CALL0_ABI__)
mov a0, a9 /* retrieve ret addr */
#endif
ret
/*******************************************************************************
_xt_context_restore
!! MUST BE CALLED ONLY BY 'CALL0' INSTRUCTION !!
Restores all Xtensa processor state except PC, PS, A0, A1 (SP) (and in Call0
ABI, A14, A15 which are preserved by all interrupt handlers) from an interrupt
stack frame defined in xtensa_rtos.h .
Its counterpart is _xt_context_save (whose caller saved A12, A13).
Caller is responsible to restore PC, PS, A0, A1 (SP).
Entry Conditions:
A0 = Return address in caller.
A1 = Stack pointer of interrupted thread or handler ("interruptee").
Exit conditions:
A0 = Return address in caller.
A1 = Stack pointer of interrupted thread or handler ("interruptee").
Other processor state except PC, PS, A0, A1 (SP), is as at the point
of interruption.
*******************************************************************************/
.global _xt_context_restore
.type _xt_context_restore,@function
.align 4
_xt_context_restore:
#if XCHAL_EXTRA_SA_SIZE > 0
/*
NOTE: Normally the xthal_restore_extra_nw macro only affects address
registers a2-a5. It is theoretically possible for Xtensa processor
designers to write TIE that causes more address registers to be
affected, but it is generally unlikely. If that ever happens,
more registers need to be saved/restored around this macro invocation.
Here we only assume a13 is preserved.
Future Xtensa tools releases might limit the regs that can be affected.
*/
mov a13, a0 /* preserve ret addr */
addi a2, sp, XT_STK_EXTRA /* where to find it */
call0 xthal_restore_extra_nw /* destroys a0,2,3,4,5 */
mov a0, a13 /* retrieve ret addr */
#endif
#if XCHAL_HAVE_LOOPS
l32i a2, sp, XT_STK_LBEG
l32i a3, sp, XT_STK_LEND
wsr a2, LBEG
l32i a2, sp, XT_STK_LCOUNT
wsr a3, LEND
wsr a2, LCOUNT
#endif
l32i a3, sp, XT_STK_SAR
l32i a2, sp, XT_STK_A2
wsr a3, SAR
l32i a3, sp, XT_STK_A3
l32i a4, sp, XT_STK_A4
l32i a5, sp, XT_STK_A5
l32i a6, sp, XT_STK_A6
l32i a7, sp, XT_STK_A7
l32i a8, sp, XT_STK_A8
l32i a9, sp, XT_STK_A9
l32i a10, sp, XT_STK_A10
l32i a11, sp, XT_STK_A11
/*
Call0 ABI callee-saved regs a12-15 do not need to be restored here.
However a12-13 were saved for scratch before XT_RTOS_INT_ENTER(),
so need to be restored anyway, despite being callee-saved in Call0.
*/
l32i a12, sp, XT_STK_A12
l32i a13, sp, XT_STK_A13
#ifndef __XTENSA_CALL0_ABI__
l32i a14, sp, XT_STK_A14
l32i a15, sp, XT_STK_A15
#endif
ret
/*******************************************************************************
_xt_coproc_init
Initializes global co-processor management data, setting all co-processors
to "unowned". Leaves CPENABLE as it found it (does NOT clear it).
Called during initialization of the RTOS, before any threads run.
This may be called from normal Xtensa single-threaded application code which
might use co-processors. The Xtensa run-time initialization enables all
co-processors. They must remain enabled here, else a co-processor exception
might occur outside of a thread, which the exception handler doesn't expect.
Entry Conditions:
Xtensa single-threaded run-time environment is in effect.
No thread is yet running.
Exit conditions:
None.
Obeys ABI conventions per prototype:
void _xt_coproc_init(void)
*******************************************************************************/
#if XCHAL_CP_NUM > 0
.global _xt_coproc_init
.type _xt_coproc_init,@function
.align 4
_xt_coproc_init:
ENTRY0
/* Initialize thread co-processor ownerships to 0 (unowned). */
movi a2, _xt_coproc_owner_sa /* a2 = base of owner array */
addi a3, a2, XCHAL_CP_MAX << 2 /* a3 = top+1 of owner array */
movi a4, 0 /* a4 = 0 (unowned) */
1: s32i a4, a2, 0
addi a2, a2, 4
bltu a2, a3, 1b
RET0
#endif
/*******************************************************************************
_xt_coproc_release
Releases any and all co-processors owned by a given thread. The thread is
identified by it's co-processor state save area defined in xtensa_context.h .
Must be called before a thread's co-proc save area is deleted to avoid
memory corruption when the exception handler tries to save the state.
May be called when a thread terminates or completes but does not delete
the co-proc save area, to avoid the exception handler having to save the
thread's co-proc state before another thread can use it (optimization).
Entry Conditions:
A2 = Pointer to base of co-processor state save area.
Exit conditions:
None.
Obeys ABI conventions per prototype:
void _xt_coproc_release(void * coproc_sa_base)
*******************************************************************************/
#if XCHAL_CP_NUM > 0
.global _xt_coproc_release
.type _xt_coproc_release,@function
.align 4
_xt_coproc_release:
ENTRY0 /* a2 = base of save area */
movi a3, _xt_coproc_owner_sa /* a3 = base of owner array */
addi a4, a3, XCHAL_CP_MAX << 2 /* a4 = top+1 of owner array */
movi a5, 0 /* a5 = 0 (unowned) */
rsil a6, XCHAL_EXCM_LEVEL /* lock interrupts */
1: l32i a7, a3, 0 /* a7 = owner at a3 */
bne a2, a7, 2f /* if (coproc_sa_base == owner) */
s32i a5, a3, 0 /* owner = unowned */
2: addi a3, a3, 1<<2 /* a3 = next entry in owner array */
bltu a3, a4, 1b /* repeat until end of array */
3: wsr a6, PS /* restore interrupts */
RET0
#endif