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ARCv2: entry: comments about hardware auto-save on taken interrupts
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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Vineet Gupta
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926150db85
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45869eb0c0
@ -7,15 +7,54 @@
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#include <asm/irqflags-arcv2.h>
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#include <asm/thread_info.h> /* For THREAD_SIZE */
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/*
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* Interrupt/Exception stack layout (pt_regs) for ARCv2
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* (End of struct aligned to end of page [unless nested])
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*
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* INTERRUPT EXCEPTION
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*
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* manual --------------------- manual
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* | orig_r0 |
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* | event/ECR |
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* | bta |
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* | user_r25 |
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* | gp |
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* | fp |
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* | sp |
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* | r12 |
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* | r30 |
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* | r58 |
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* | r59 |
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* hw autosave ---------------------
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* optional | r0 |
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* | r1 |
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* ~ ~
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* | r9 |
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* | r10 |
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* | r11 |
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* | blink |
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* | lpe |
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* | lps |
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* | lpc |
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* | ei base |
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* | ldi base |
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* | jli base |
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* ---------------------
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* hw autosave | pc / eret |
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* mandatory | stat32 / erstatus |
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* ---------------------
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*/
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/*------------------------------------------------------------------------*/
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.macro INTERRUPT_PROLOGUE called_from
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; Before jumping to Interrupt Vector, hardware micro-ops did following:
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; (A) Before jumping to Interrupt Vector, hardware micro-ops did following:
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; 1. SP auto-switched to kernel mode stack
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; 2. STATUS32.Z flag set to U mode at time of interrupt (U:1, K:0)
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; 3. Auto saved: r0-r11, blink, LPE,LPS,LPC, JLI,LDI,EI, PC, STAT32
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; 2. STATUS32.Z flag set if in U mode at time of interrupt (U:1,K:0)
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; 3. Auto save: (mandatory) Push PC and STAT32 on stack
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; hardware does even if CONFIG_ARC_IRQ_NO_AUTOSAVE
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; 4. Auto save: (optional) r0-r11, blink, LPE,LPS,LPC, JLI,LDI,EI
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;
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; Now manually save: r12, sp, fp, gp, r25
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; (B) Manually saved some regs: r12,r25,r30, sp,fp,gp, ACCL pair
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#ifdef CONFIG_ARC_IRQ_NO_AUTOSAVE
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.ifnc \called_from, exception
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@ -57,14 +96,17 @@
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; - U mode: retrieve it from AUX_USER_SP
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; - K mode: add the offset from current SP where H/w starts auto push
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;
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; Utilize the fact that Z bit is set if Intr taken in U mode
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; 1. Utilize the fact that Z bit is set if Intr taken in U mode
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; 2. Upon entry SP is always saved (for any inspection, unwinding etc),
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; but on return, restored only if U mode
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mov.nz r9, sp
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add.nz r9, r9, SZ_PT_REGS - PT_sp - 4
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add.nz r9, r9, SZ_PT_REGS - PT_sp - 4 ; K mode SP
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bnz 1f
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lr r9, [AUX_USER_SP]
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lr r9, [AUX_USER_SP] ; U mode SP
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1:
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PUSH r9 ; SP
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PUSH r9 ; SP (pt_regs->sp)
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PUSH fp
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PUSH gp
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@ -85,6 +127,8 @@
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/*------------------------------------------------------------------------*/
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.macro INTERRUPT_EPILOGUE called_from
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; INPUT: r0 has STAT32 of calling context
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; INPUT: Z flag set if returning to K mode
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.ifnc \called_from, exception
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add sp, sp, 12 ; skip BTA/ECR/orig_r0 placeholderss
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.endif
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@ -98,9 +142,10 @@
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POP gp
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POP fp
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; Don't touch AUX_USER_SP if returning to K mode (Z bit set)
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; (Z bit set on K mode is inverse of INTERRUPT_PROLOGUE)
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add.z sp, sp, 4
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; Restore SP (into AUX_USER_SP) only if returning to U mode
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; - for K mode, it will be implicitly restored as stack is unwound
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; - Z flag set on K is inverse of what hardware does on interrupt entry
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; but that doesn't really matter
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bz 1f
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POPAX AUX_USER_SP
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@ -145,11 +190,11 @@
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/*------------------------------------------------------------------------*/
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.macro EXCEPTION_PROLOGUE
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; Before jumping to Exception Vector, hardware micro-ops did following:
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; (A) Before jumping to Exception Vector, hardware micro-ops did following:
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; 1. SP auto-switched to kernel mode stack
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; 2. STATUS32.Z flag set to U mode at time of interrupt (U:1,K:0)
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; 2. STATUS32.Z flag set if in U mode at time of exception (U:1,K:0)
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;
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; Now manually save the complete reg file
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; (B) Manually save the complete reg file below
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PUSH r9 ; freeup a register: slot of erstatus
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@ -195,12 +240,13 @@
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PUSHAX ecr ; r9 contains ECR, expected by EV_Trap
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PUSH r0 ; orig_r0
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; OUTPUT: r9 has ECR
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.endm
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/*------------------------------------------------------------------------*/
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.macro EXCEPTION_EPILOGUE
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; Assumes r0 has PT_status32
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; INPUT: r0 has STAT32 of calling context
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btst r0, STATUS_U_BIT ; Z flag set if K, used in INTERRUPT_EPILOGUE
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add sp, sp, 8 ; orig_r0/ECR don't need restoring
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