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Save/restore coprocessor state on stack #2057

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Sep 2, 2024
Merged

Save/restore coprocessor state on stack #2057

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bugadani Sep 2, 2024
db62b20
Save and restore coprocessor enable state
bugadani Sep 2, 2024
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141 changes: 72 additions & 69 deletions xtensa-lx-rt/src/exception/asm.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,25 +11,25 @@ use crate::cfg_asm;
// Additionally there is a chunk of memory reserved for spilled registers.
global_asm!(
"
.set XT_STK_PC, 0
.set XT_STK_PS, 4
.set XT_STK_A0, 8
.equ XT_STK_A1, 12
.set XT_STK_A2, 16
.set XT_STK_A3, 20
.set XT_STK_A4, 24
.set XT_STK_A5, 28
.set XT_STK_A6, 32
.set XT_STK_A7, 36
.set XT_STK_A8, 40
.set XT_STK_A9, 44
.set XT_STK_A10, 48
.set XT_STK_A11, 52
.set XT_STK_A12, 56
.set XT_STK_A13, 60
.set XT_STK_A14, 64
.set XT_STK_A15, 68
.set XT_STK_SAR, 72
.set XT_STK_PC, 0
.set XT_STK_PS, 4
.set XT_STK_A0, 8
.equ XT_STK_A1, 12
.set XT_STK_A2, 16
.set XT_STK_A3, 20
.set XT_STK_A4, 24
.set XT_STK_A5, 28
.set XT_STK_A6, 32
.set XT_STK_A7, 36
.set XT_STK_A8, 40
.set XT_STK_A9, 44
.set XT_STK_A10, 48
.set XT_STK_A11, 52
.set XT_STK_A12, 56
.set XT_STK_A13, 60
.set XT_STK_A14, 64
.set XT_STK_A15, 68
.set XT_STK_SAR, 72
.set XT_STK_EXCCAUSE, 76
.set XT_STK_EXCVADDR, 80
.set XT_STK_LBEG, 84 // Registers for Loop Option
Expand Down Expand Up @@ -66,6 +66,7 @@ global_asm!(
.set XT_STK_F14, 208
.set XT_STK_F15, 212
.set XT_STK_TMP, 216
.set XT_STK_CPENABLE, 220

.set XT_STK_FRMSZ, 256 // needs to be multiple of 16 and enough additional free space
// for the registers spilled to the stack (max 8 registers / 0x20 bytes)
Expand Down Expand Up @@ -126,6 +127,8 @@ unsafe extern "C" fn save_context() {
#[cfg(all(XCHAL_HAVE_CP, not(feature = "float-save-restore")))]
"
/* Disable coprocessor, any use of floats in ISRs will cause an exception unless float-save-restore feature is enabled */
rsr a3, CPENABLE
s32i a3, sp, +XT_STK_CPENABLE
movi a3, 0
wsr a3, CPENABLE
rsync
Expand Down Expand Up @@ -177,11 +180,11 @@ unsafe extern "C" fn save_context() {
#[cfg(all(feature = "float-save-restore", XCHAL_HAVE_DFP_ACCEL))]
"
// Double Precision Accelerator Option
rur a3, f64r_lo
rur a3, f64r_lo
s32i a3, sp, +XT_STK_F64R_LO
rur a3, f64r_hi
s32i a3, sp, +XT_STK_F64R_HI
rur a3, f64s
rur a3, f64s
s32i a3, sp, +XT_STK_F64S
",
#[cfg(all(feature = "float-save-restore", XCHAL_HAVE_FP))]
Expand Down Expand Up @@ -226,7 +229,7 @@ unsafe extern "C" fn save_context() {
// used as a temporary by this code, the temporary value would get stored
// onto the stack, instead of the real value.
//

rsr a2, PS // to be restored after SPILL_REGISTERS
movi a0, PS_INTLEVEL_MASK
and a3, a2, a0 // get the current INTLEVEL
Expand All @@ -237,11 +240,11 @@ unsafe extern "C" fn save_context() {
or a3, a3, a0
wsr a3, ps
rsr a0, EPC1

addmi sp, sp, +XT_STK_FRMSZ // go back to spill register region
SPILL_REGISTERS
addmi sp, sp, -XT_STK_FRMSZ // return the current stack pointer

wsr a2, PS // restore to the value at entry
rsync
wsr a0, EPC1
Expand Down Expand Up @@ -288,9 +291,9 @@ global_asm!(
// file on an LX6 core (ESP-32) I'm measuring 145 cycles to spill
// registers with this vs. 279 (!) to do it with
// xthal_spill_windows().

.macro SPILL_REGISTERS
and a12, a12, a12
and a12, a12, a12
rotw 3
and a12, a12, a12
rotw 3
Expand All @@ -311,10 +314,10 @@ global_asm!(
addmi sp, sp, -XT_STK_FRMSZ // only allow multiple of 256

s32i a0, sp, +XT_STK_A1 // save interruptee's A1/SP
s32e a0, sp, -12 // for debug backtrace
s32e a0, sp, -12 // for debug backtrace

.ifc \level,1
rsr a0, PS
rsr a0, PS
s32i a0, sp, +XT_STK_PS // save interruptee's PS

rsr a0, EXCCAUSE
Expand All @@ -323,15 +326,15 @@ global_asm!(
s32i a0, sp, +XT_STK_EXCVADDR
.else
rsr a0, EPS\level
s32i a0, sp, +XT_STK_PS // save interruptee's PS
s32i a0, sp, +XT_STK_PS // save interruptee's PS
.endif

rsr a0, EPC\level
s32i a0, sp, +XT_STK_PC // save interruptee's PC
s32e a0, sp, -16 // for debug backtrace
rsr a0, EPC\level
s32i a0, sp, +XT_STK_PC // save interruptee's PC
s32e a0, sp, -16 // for debug backtrace

rsr a0, EXCSAVE\level
s32i a0, sp, +XT_STK_A0 // save interruptee's A0
rsr a0, EXCSAVE\level
s32i a0, sp, +XT_STK_A0 // save interruptee's A0

call0 save_context

Expand Down Expand Up @@ -429,8 +432,8 @@ unsafe extern "C" fn restore_context() {
",
#[cfg(all(XCHAL_HAVE_CP, not(feature = "float-save-restore")))]
"
/* Re-enable coprocessor(s) after ISR */
movi a3, 8 /* XCHAL_CP_MAXCFG */
/* Restore coprocessor state after ISR */
l32i a3, sp, +XT_STK_CPENABLE
wsr a3, CPENABLE
rsync
",
Expand Down Expand Up @@ -458,26 +461,26 @@ unsafe extern "C" fn restore_context() {
global_asm!(
r#"
.macro RESTORE_CONTEXT level:req
// Restore context and return

// Restore context and return
call0 restore_context

.ifc \level,1
l32i a0, sp, +XT_STK_PS // retrieve interruptee's PS
l32i a0, sp, +XT_STK_PS // retrieve interruptee's PS
wsr a0, PS
l32i a0, sp, +XT_STK_PC // retrieve interruptee's PC
l32i a0, sp, +XT_STK_PC // retrieve interruptee's PC
wsr a0, EPC\level
.else
l32i a0, sp, +XT_STK_PS // retrieve interruptee's PS
l32i a0, sp, +XT_STK_PS // retrieve interruptee's PS
wsr a0, EPS\level
l32i a0, sp, +XT_STK_PC // retrieve interruptee's PC
wsr a0, EPC\level
.endif

l32i a0, sp, +XT_STK_A0 // retrieve interruptee's A0
l32i sp, sp, +XT_STK_A1 // remove exception frame
rsync // ensure PS and EPC written
l32i a0, sp, +XT_STK_PC // retrieve interruptee's PC
wsr a0, EPC\level
.endif

l32i a0, sp, +XT_STK_A0 // retrieve interruptee's A0
l32i sp, sp, +XT_STK_A1 // remove exception frame
rsync // ensure PS and EPC written

.endm
"#
);
Expand Down Expand Up @@ -518,8 +521,8 @@ unsafe extern "C" fn __default_naked_exception() {

.RestoreContext:
RESTORE_CONTEXT 1
rfe // PS.EXCM is cleared

rfe // PS.EXCM is cleared
",
options(noreturn)
)
Expand All @@ -539,44 +542,44 @@ unsafe extern "C" fn __default_naked_double_exception() {
"
mov a0, a1 // save a1/sp
addmi sp, sp, -XT_STK_FRMSZ // only allow multiple of 256

s32i a0, sp, +XT_STK_A1 // save interruptee's A1/SP
s32e a0, sp, -12 // for debug backtrace
rsr a0, PS
s32e a0, sp, -12 // for debug backtrace

rsr a0, PS
s32i a0, sp, +XT_STK_PS // save interruptee's PS

rsr a0, EXCCAUSE
s32i a0, sp, +XT_STK_EXCCAUSE
rsr a0, EXCVADDR
s32i a0, sp, +XT_STK_EXCVADDR
rsr a0, DEPC
s32i a0, sp, +XT_STK_PC // save interruptee's PC
s32e a0, sp, -16 // for debug backtrace

rsr a0, DEPC
s32i a0, sp, +XT_STK_PC // save interruptee's PC
s32e a0, sp, -16 // for debug backtrace

rsr a0, EXCSAVE7 // ok to reuse EXCSAVE7 for double exception as long as
// double exception is not in first couple of instructions
// of level 7 handler
s32i a0, sp, +XT_STK_A0 // save interruptee's A0
s32i a0, sp, +XT_STK_A0 // save interruptee's A0

call0 save_context

l32i a6, sp, +XT_STK_EXCCAUSE // put cause in a6 = a2 in callee
mov a7, sp // put address of save frame in a7=a3 in callee
call4 __exception // call handler <= actual call!

// Restore context and return
// Restore context and return
call0 restore_context

l32i a0, sp, +XT_STK_PS // retrieve interruptee's PS
l32i a0, sp, +XT_STK_PS // retrieve interruptee's PS
wsr a0, PS
l32i a0, sp, +XT_STK_PC // retrieve interruptee's PC
l32i a0, sp, +XT_STK_PC // retrieve interruptee's PC
wsr a0, EPC1

l32i a0, sp, +XT_STK_A0 // retrieve interruptee's A0
l32i sp, sp, +XT_STK_A1 // remove exception frame
rsync // ensure PS and EPC written
l32i a0, sp, +XT_STK_A0 // retrieve interruptee's A0
l32i sp, sp, +XT_STK_A1 // remove exception frame
rsync // ensure PS and EPC written

rfde
",
Expand Down