Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 5fe86ad6 authored by Vineet Gupta's avatar Vineet Gupta Committed by Greg Kroah-Hartman
Browse files

ARCv2: entry: comments about hardware auto-save on taken interrupts 



[ Upstream commit 45869eb0c0afd72bd5ab2437d4b00915697c044a ]

Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
Stable-dep-of: 92e2921eeafd ("ARC: define ASM_NL and __ALIGN(_STR) outside #ifdef __ASSEMBLY__ guard")
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 71c68777

arch/arc/include/asm/entry-arcv2.h

+62 −16
Original line number Diff line number Diff line
@@ -7,15 +7,54 @@ 
#include <asm/irqflags-arcv2.h>

#include <asm/thread_info.h>	/* For THREAD_SIZE */



/*

 * Interrupt/Exception stack layout (pt_regs) for ARCv2

 *   (End of struct aligned to end of page [unless nested])

 *

 *  INTERRUPT                          EXCEPTION

 *

 *    manual    ---------------------  manual

 *              |      orig_r0      |

 *              |      event/ECR    |

 *              |      bta          |

 *              |      user_r25     |

 *              |      gp           |

 *              |      fp           |

 *              |      sp           |

 *              |      r12          |

 *              |      r30          |

 *              |      r58          |

 *              |      r59          |

 *  hw autosave ---------------------

 *    optional  |      r0           |

 *              |      r1           |

 *              ~                   ~

 *              |      r9           |

 *              |      r10          |

 *              |      r11          |

 *              |      blink        |

 *              |      lpe          |

 *              |      lps          |

 *              |      lpc          |

 *              |      ei base      |

 *              |      ldi base     |

 *              |      jli base     |

 *              ---------------------

 *  hw autosave |       pc / eret   |

 *   mandatory  | stat32 / erstatus |

 *              ---------------------

 */



/*------------------------------------------------------------------------*/

.macro INTERRUPT_PROLOGUE	called_from



	; Before jumping to Interrupt Vector, hardware micro-ops did following:

	; (A) Before jumping to Interrupt Vector, hardware micro-ops did following:

	;   1. SP auto-switched to kernel mode stack

	;   2. STATUS32.Z flag set to U mode at time of interrupt (U:1, K:0)

	;   3. Auto saved: r0-r11, blink, LPE,LPS,LPC, JLI,LDI,EI, PC, STAT32

	;   2. STATUS32.Z flag set if in U mode at time of interrupt (U:1,K:0)

	;   3. Auto save: (mandatory) Push PC and STAT32 on stack

	;                 hardware does even if CONFIG_ARC_IRQ_NO_AUTOSAVE

	;   4. Auto save: (optional) r0-r11, blink, LPE,LPS,LPC, JLI,LDI,EI

	;

	; Now manually save: r12, sp, fp, gp, r25

	; (B) Manually saved some regs: r12,r25,r30, sp,fp,gp, ACCL pair



#ifdef CONFIG_ARC_IRQ_NO_AUTOSAVE

.ifnc \called_from, exception
@@ -57,14 +96,17 @@ 
	;  - U mode: retrieve it from AUX_USER_SP

	;  - K mode: add the offset from current SP where H/w starts auto push

	;

	; Utilize the fact that Z bit is set if Intr taken in U mode

	; 1. Utilize the fact that Z bit is set if Intr taken in U mode

	; 2. Upon entry SP is always saved (for any inspection, unwinding etc),

	;    but on return, restored only if U mode



	mov.nz	r9, sp

	add.nz	r9, r9, SZ_PT_REGS - PT_sp - 4

	add.nz	r9, r9, SZ_PT_REGS - PT_sp - 4		; K mode SP

	bnz	1f



	lr	r9, [AUX_USER_SP]

	lr	r9, [AUX_USER_SP]			; U mode SP

1:

	PUSH	r9	; SP

	PUSH	r9					; SP (pt_regs->sp)



	PUSH	fp

	PUSH	gp
@@ -85,6 +127,8 @@ 
/*------------------------------------------------------------------------*/

.macro INTERRUPT_EPILOGUE	called_from



	; INPUT: r0 has STAT32 of calling context

	; INPUT: Z flag set if returning to K mode

.ifnc \called_from, exception

	add	sp, sp, 12	; skip BTA/ECR/orig_r0 placeholderss

.endif
@@ -98,9 +142,10 @@ 
	POP	gp

	POP	fp



	; Don't touch AUX_USER_SP if returning to K mode (Z bit set)

	; (Z bit set on K mode is inverse of INTERRUPT_PROLOGUE)

	add.z	sp, sp, 4

	; Restore SP (into AUX_USER_SP) only if returning to U mode

	;  - for K mode, it will be implicitly restored as stack is unwound

	;  - Z flag set on K is inverse of what hardware does on interrupt entry

	;    but that doesn't really matter

	bz	1f



	POPAX	AUX_USER_SP
@@ -145,11 +190,11 @@ 
/*------------------------------------------------------------------------*/

.macro EXCEPTION_PROLOGUE



	; Before jumping to Exception Vector, hardware micro-ops did following:

	; (A) Before jumping to Exception Vector, hardware micro-ops did following:

	;   1. SP auto-switched to kernel mode stack

	;   2. STATUS32.Z flag set to U mode at time of interrupt (U:1,K:0)

	;   2. STATUS32.Z flag set if in U mode at time of exception (U:1,K:0)

	;

	; Now manually save the complete reg file

	; (B) Manually save the complete reg file below



	PUSH	r9		; freeup a register: slot of erstatus
@@ -195,12 +240,13 @@ 
	PUSHAX	ecr		; r9 contains ECR, expected by EV_Trap



	PUSH	r0		; orig_r0

	; OUTPUT: r9 has ECR

.endm



/*------------------------------------------------------------------------*/

.macro EXCEPTION_EPILOGUE



	; Assumes r0 has PT_status32

	; INPUT: r0 has STAT32 of calling context

	btst   r0, STATUS_U_BIT	; Z flag set if K, used in INTERRUPT_EPILOGUE



	add	sp, sp, 8	; orig_r0/ECR don't need restoring