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esp-open-rtos/core/exception_vectors.S
Angus Gratton 23ea182e83 Simplify interrupt and RTOS timer tick handlers 
RTOS Timer tick handler is now the same as any other ISR.

This causes a few subtle behaviour changes that seem OK but are worth noting:

* RTOS tick handler sdk__xt_timer_int() is now called from one stack
  frame deeper (inside _xt_isr_handler()), whereas before it was called
  from the level above in UserHandleInterrupt. I can't see any way that
  the extra ~40 bytes of stack use here hurt, though.

* sdk__xt_timer_int() was previous called after all other interrupts
  flagged in the handler, now it's called before the TIMER FRC1 & FRC2
  handlers. The tick handler doesn't appear to do anything particularly
  timing intensive, though.

* GPIO interrupt (value 3) is now lower priority than the SPI
  interrupt (value 2), whereas before it would have been called before
  SPI if both interrupts triggered at once.
2015-09-29 13:21:04 +10:00

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/* Xtensa Exception (ie interrupt) Vectors & low-level handler code
*
* Core exception handler code is placed in the .vecbase section, which gets
* picked up specially in the linker script and placed at beginning of IRAM.
*
* The actual VecBase symbol should be the first thing in .vecbase (this is not
* strictly important as it gets set by symbol lookup not by hardcoded address,
* but having it at 0x40100000 means that the exception vectors have memorable
* offsets, which match the default Boot ROM vector offsets. So convenient for
* human understanding.
*
* Part of esp-open-rtos
* Original vector contents Copyright (C) 2014-2015 Espressif Systems
* Additions Copyright (C) Superhouse Automation Pty Ltd and Angus Gratton
* BSD Licensed as described in the file LICENSE
*/
#include "led_debug.s"
/* Some UserException causes, see table Table 4–64 in ISA reference */
#define CAUSE_SYSCALL 1
#define CAUSE_LOADSTORE 3
#define CAUSE_LVL1INT 4
.section .bss
NMIHandlerStack: # stack space for NMI handler
.skip 4*0x100
.LNMIHandlerStackTop:
NMIRegisterSaved: # register space for saving NMI registers
.skip 4*(16 + 6)
LoadStoreErrorHandlerStack:
.word 0 # a0
.word 0 # (unused)
.word 0 # a2
.word 0 # a3
.word 0 # a4
/***************************** Exception Vectors *****************************/
.section .vecbase.text, "x"
/* Note: Exception vectors must be aligned on a 256-byte (0x100) boundary or
* they will not function properly. (This is taken care of in the linker
* script by ensuring .vecbase.text is aligned properly, and putting VecBase
* right at the beginning of .vecbase.text) */
.org 0
VecBase:
.global VecBase
/* IMPORTANT: exception vector literals will go here, but we
* can't have more than 4 otherwise we push DebugExceptionVector past
* offset 0x10 relative to VecBase. There should be ways to avoid this,
* and also keep the VecBase offsets easy to read, but this works for
* now. */
.literal_position
.org VecBase + 0x10
DebugExceptionVector:
.type DebugExceptionVector, @function
wsr a0, excsave2
call0 sdk_user_fatal_exception_handler
rfi 2
.org VecBase + 0x20
NMIExceptionVector:
.type NMIExceptionVector, @function
wsr a0, excsave3
call0 CallNMIExceptionHandler
rfi 3 # Should never be reached
.org VecBase + 0x30
KernelExceptionVector:
.type KernelExceptionVector, @function
break 1, 0
call0 sdk_user_fatal_exception_handler
rfe
.org VecBase + 0x50
UserExceptionVector:
.type UserExceptionVector, @function
wsr a1, excsave1
rsr a1, exccause
beqi a1, CAUSE_LOADSTORE, LoadStoreErrorHandler
j UserExceptionHandler
.org VecBase + 0x70
DoubleExceptionVector:
.type DoubleExceptionVector, @function
break 1, 4
call0 sdk_user_fatal_exception_handler
/* Reset vector at offset 0x80 is unused, as vecbase gets reset to mask ROM
* vectors on chip reset. */
/*************************** LoadStoreError Handler **************************/
.section .vecbase.text, "x"
/* Xtensa "Load/Store Exception" handler:
* Completes L8/L16 load instructions from Instruction address space, for which
* the architecture only supports 32-bit reads.
*
* Called from UserExceptionVector if EXCCAUSE is LoadStoreErrorCause
*
* (Fast path (no branches) is for L8UI)
*/
.literal_position
.balign 4
LoadStoreErrorHandler:
.type LoadStoreErrorHandler, @function
/* Registers are saved in the address corresponding to their register
* number times 4. This allows a quick and easy mapping later on when
* needing to store the value to a particular register number. */
movi sp, LoadStoreErrorHandlerStack
s32i a0, sp, 0
s32i a2, sp, 0x08
s32i a3, sp, 0x0c
s32i a4, sp, 0x10
rsr a0, sar # Save SAR in a0 to restore later
/* Examine the opcode which generated the exception */
/* Note: Instructions are in this order to avoid pipeline stalls. */
rsr a2, epc1
movi a3, ~3
ssa8l a2 # sar is now correct shift for aligned read
and a2, a2, a3 # a2 now 4-byte aligned address of instruction
l32i a4, a2, 0
l32i a2, a2, 4
movi a3, 0x00700F # opcode mask for l8ui/l16si/l16ui
src a2, a2, a4 # a2 now instruction that failed
and a3, a2, a3 # a3 is masked instruction
bnei a3, 0x000002, .LSE_check_l16
/* Note: At this point, opcode could technically be one of two things:
* xx0xx2 (L8UI)
* xx8xx2 (Reserved (invalid) opcode)
* It is assumed that we'll never get to this point from an illegal
* opcode, so we don't bother to check for that case and presume this
* is always an L8UI. */
movi a4, ~3
rsr a3, excvaddr # read faulting address
and a4, a3, a4 # a4 now word aligned read address
l32i a4, a4, 0 # perform the actual read
ssa8l a3 # sar is now shift to extract a3's byte
srl a3, a4 # shift right correct distance
extui a4, a3, 0, 8 # mask off bits we need for an l8
.LSE_post_fetch:
/* We jump back here after either the L8UI or the L16*I routines do the
* necessary work to read the value from memory.
* At this point, a2 holds the faulting instruction and a4 holds the
* correctly read value.
* Restore original SAR value (saved in a0) and update EPC so we'll
* return back to the instruction following the one we just emulated */
/* Note: Instructions are in this order to avoid pipeline stalls */
rsr a3, epc1
wsr a0, sar
addi a3, a3, 0x3
wsr a3, epc1
/* Stupid opcode tricks: The jumptable we use later on needs 16 bytes
* per entry (so we can avoid a second jump by just doing a RFE inside
* each entry). Unfortunately, however, Xtensa doesn't have an addx16
* operation to make that easy for us. Luckily, all of the faulting
* opcodes we're processing are guaranteed to have bit 3 be zero, which
* means if we just shift the register bits of the opcode down by 3
* instead of 4, we will get the register number multiplied by 2. This
* combined with an addx8 will give us an effective addx16 without
* needing any extra shift operations. */
extui a2, a2, 3, 5 # a2 is now destination register 0-15 times 2
bgei a2, 10, .LSE_assign_reg # a5..a15 use jumptable
beqi a2, 2, .LSE_assign_a1 # a1 uses a special routine
/* We're storing into a0 or a2..a4, which are all saved in our "stack"
* area. Calculate the correct address and stick the value in there,
* then just do our normal restore and RFE (no jumps required, which
* actually makes a0..a4 substantially faster). */
addx2 a2, a2, sp
s32i a4, a2, 0
/* Restore all regs and return */
l32i a0, sp, 0
l32i a2, sp, 0x08
l32i a3, sp, 0x0c
l32i a4, sp, 0x10
rsr a1, excsave1 # restore a1 saved by UserExceptionVector
rfe
.LSE_assign_reg:
/* At this point, a2 contains the register number times 2, a4 is the
* read value. */
/* Calculate the jumptable address, and restore all regs except a2 and
* a4 so we have less to do after jumping. */
/* Note: Instructions are in this order to avoid pipeline stalls. */
movi a3, .LSE_jumptable_base
l32i a0, sp, 0
addx8 a2, a2, a3 # a2 is now the address to jump to
l32i a3, sp, 0x0c
jx a2
.balign 4
.LSE_check_l16:
/* At this point, a2 contains the opcode, a3 is masked opcode */
movi a4, 0x001002 # l16si or l16ui opcode after masking
bne a3, a4, .LSE_wrong_opcode
/* Note: At this point, the opcode could be one of two things:
* xx1xx2 (L16UI)
* xx9xx2 (L16SI)
* Both of these we can handle. */
movi a4, ~3
rsr a3, excvaddr # read faulting address
and a4, a3, a4 # a4 now word aligned read address
l32i a4, a4, 0 # perform the actual read
ssa8l a3 # sar is now shift to extract a3's bytes
srl a3, a4 # shift right correct distance
extui a4, a3, 0, 16 # mask off bits we need for an l16
bbci a2, 15, .LSE_post_fetch # Not a signed op
bbci a4, 15, .LSE_post_fetch # Value does not need sign-extension
movi a3, 0xFFFF0000
or a4, a3, a4 # set 32-bit sign bits
j .LSE_post_fetch
.LSE_wrong_opcode:
/* If we got here it's not an opcode we can try to fix, so bomb out.
* Restore registers so any dump the fatal exception routine produces
* will have correct values */
wsr a0, sar
l32i a0, sp, 0
l32i a2, sp, 0x08
l32i a3, sp, 0x0c
l32i a4, sp, 0x10
rsr a1, excsave1
call0 sdk_user_fatal_exception_handler
.balign 4
.LSE_assign_a1:
/* a1 is saved in excsave1, so just update that with the value, */
wsr a4, excsave1
/* Then restore all regs and return */
l32i a0, sp, 0
l32i a2, sp, 0x08
l32i a3, sp, 0x0c
l32i a4, sp, 0x10
rsr a1, excsave1
rfe
.balign 4
.LSE_jumptable:
/* The first 5 entries (80 bytes) of this table are unused (registers
* a0..a4 are handled separately above). Rather than have a whole bunch
* of wasted space, we just pretend that the table starts 80 bytes
* earlier in memory. */
.set .LSE_jumptable_base, .LSE_jumptable - (16 * 5)
.org .LSE_jumptable_base + (16 * 5)
mov a5, a4
l32i a2, sp, 0x08
l32i a4, sp, 0x10
rsr a1, excsave1
rfe
.org .LSE_jumptable_base + (16 * 6)
mov a6, a4
l32i a2, sp, 0x08
l32i a4, sp, 0x10
rsr a1, excsave1
rfe
.org .LSE_jumptable_base + (16 * 7)
mov a7, a4
l32i a2, sp, 0x08
l32i a4, sp, 0x10
rsr a1, excsave1
rfe
.org .LSE_jumptable_base + (16 * 8)
mov a8, a4
l32i a2, sp, 0x08
l32i a4, sp, 0x10
rsr a1, excsave1
rfe
.org .LSE_jumptable_base + (16 * 9)
mov a9, a4
l32i a2, sp, 0x08
l32i a4, sp, 0x10
rsr a1, excsave1
rfe
.org .LSE_jumptable_base + (16 * 10)
mov a10, a4
l32i a2, sp, 0x08
l32i a4, sp, 0x10
rsr a1, excsave1
rfe
.org .LSE_jumptable_base + (16 * 11)
mov a11, a4
l32i a2, sp, 0x08
l32i a4, sp, 0x10
rsr a1, excsave1
rfe
.org .LSE_jumptable_base + (16 * 12)
mov a12, a4
l32i a2, sp, 0x08
l32i a4, sp, 0x10
rsr a1, excsave1
rfe
.org .LSE_jumptable_base + (16 * 13)
mov a13, a4
l32i a2, sp, 0x08
l32i a4, sp, 0x10
rsr a1, excsave1
rfe
.org .LSE_jumptable_base + (16 * 14)
mov a14, a4
l32i a2, sp, 0x08
l32i a4, sp, 0x10
rsr a1, excsave1
rfe
.org .LSE_jumptable_base + (16 * 15)
mov a15, a4
l32i a2, sp, 0x08
l32i a4, sp, 0x10
rsr a1, excsave1
rfe
/****************************** call_user_start ******************************/
.section .vecbase.text, "x"
/* This is the first entrypoint called from the ROM after loading the image
* into IRAM. It just sets up the VECBASE register to point at our own
* exception vectors and then calls sdk_user_start() */
.literal_position
.balign 4
call_user_start:
.global call_user_start
.type call_user_start, @function
movi a2, VecBase
wsr a2, vecbase
call0 sdk_user_start
/*************************** NMI Exception Handler ***************************/
.section .vecbase.text, "x"
/* Save register relative to a0 */
.macro SAVE_REG register, regnum
s32i \register, a0, (4 * (\regnum + 6))
.endm
/* Load register relative to sp */
.macro LOAD_REG register, regnum
l32i \register, sp, (4 * (\regnum + 6))
.endm
.literal_position
.balign 16
CallNMIExceptionHandler:
.type CallNMIExceptionHandler, @function
movi a0, NMIRegisterSaved
SAVE_REG a2, 2
SAVE_REG sp, 1
SAVE_REG a3, 3
rsr a2, excsave3 # a2 is now former a0
SAVE_REG a4, 4
SAVE_REG a2, 0
rsr a3, epc1
rsr a4, exccause
SAVE_REG a3, -5
SAVE_REG a4, -4
rsr a3, excvaddr
SAVE_REG a3, -3
rsr a3, excsave1
SAVE_REG a3, -2
SAVE_REG a5, 5
SAVE_REG a6, 6
SAVE_REG a7, 7
SAVE_REG a8, 8
SAVE_REG a9, 9
SAVE_REG a10, 10
SAVE_REG a11, 11
SAVE_REG a12, 12
SAVE_REG a13, 13
SAVE_REG a14, 14
SAVE_REG a15, 15
movi sp, .LNMIHandlerStackTop
movi a0, 0
movi a2, 0x23 # argument for handler
wsr a2, ps
rsync
rsr a14, sar
s32i a14, sp, 0 # this is also NMIRegisterSaved+0
call0 sdk_wDev_ProcessFiq
l32i a15, sp, 0
wsr a15, sar
movi a2, 0x33
wsr a2, ps
rsync
LOAD_REG a4, 4
LOAD_REG a5, 5
LOAD_REG a6, 6
LOAD_REG a7, 7
LOAD_REG a8, 8
LOAD_REG a9, 9
LOAD_REG a10, 10
LOAD_REG a11, 11
LOAD_REG a12, 12
LOAD_REG a13, 13
LOAD_REG a14, 14
LOAD_REG a15, 15
LOAD_REG a2, -5
LOAD_REG a3, -4
wsr a2, epc1
wsr a3, exccause
LOAD_REG a2, -3
LOAD_REG a3, -2
wsr a2, excvaddr
wsr a3, excsave1
LOAD_REG a0, 0
/* set dport nmi status bit 0 (wDev_ProcessFiq clears & verifies this
* bit stays cleared, see
* http://esp8266-re.foogod.com/wiki/WDev_ProcessFiq_%28IoT_RTOS_SDK_0.9.9%29)
*/
movi a2, 0x3ff00000
movi a3, 0x1
s32i a3, a2, 0
LOAD_REG a2, 2
LOAD_REG a3, 3
LOAD_REG a1, 1
rfi 3
/*********************** General UserException Handler ***********************/
.section .vecbase.text, "x"
/* Called by UserExceptionVector if EXCCAUSE is anything other than
* LoadStoreCause. */
.literal_position
.balign 4
UserExceptionHandler:
.type UserExceptionHandler, @function
xsr a0, excsave1 # a0 now contains sp
mov sp, a0
addi sp, sp, -0x50
s32i a0, sp, 0x10
rsr a0, ps
s32i a0, sp, 0x08
rsr a0, epc1
s32i a0, sp, 0x04
rsr a0, excsave1
s32i a0, sp, 0x0c
movi a0, _xt_user_exit
s32i a0, sp, 0x0
call0 sdk__xt_int_enter
movi a0, 0x23
wsr a0, ps
rsync
rsr a2, exccause
/* Any UserException cause other than a level 1 interrupt is fatal */
bnei a2, CAUSE_LVL1INT, .UserFailOtherExceptionCause
.UserHandleInterrupt:
rsil a0, 1
rsr a2, intenable
rsr a3, interrupt
movi a4, 0x3fff
and a2, a2, a3
and a2, a2, a4 # a2 = 0x3FFF & INTENABLE & INTERRUPT
call0 _xt_isr_handler
j sdk__xt_int_exit # once finished, jumps to _xt_user_exit via stack
.literal_position
.UserFailOtherExceptionCause:
break 1, 1
call0 sdk_user_fatal_exception_handler
/* _xt_user_exit is pushed onto the stack as part of the user exception handler,
restores same set registers which were saved there and returns from exception */
_xt_user_exit:
.global _xt_user_exit
.type _xt_user_exit, @function
l32i a0, sp, 0x8
wsr a0, ps
l32i a0, sp, 0x4
wsr a0, epc1
l32i a0, sp, 0xc
l32i sp, sp, 0x10
rsync
rfe
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