arch/arm/kernel/iwmmxt.S - linux - Git at Google

 /* SPDX-License-Identifier: GPL-2.0-only */
 /*
  *  linux/arch/arm/kernel/iwmmxt.S
  *
  *  XScale iWMMXt (Concan) context switching and handling
  *
  *  Initial code:
  *  Copyright (c) 2003, Intel Corporation
  *
  *  Full lazy switching support, optimizations and more, by Nicolas Pitre
 *   Copyright (c) 2003-2004, MontaVista Software, Inc.
  */

 #include <linux/linkage.h>
 #include <asm/ptrace.h>
 #include <asm/thread_info.h>
 #include <asm/asm-offsets.h>
 #include <asm/assembler.h>
 #include "iwmmxt.h"

 #if defined(CONFIG_CPU_PJ4) || defined(CONFIG_CPU_PJ4B)
 #define PJ4(code...)		code
 #define XSC(code...)
 #elif defined(CONFIG_CPU_MOHAWK) || \
 	defined(CONFIG_CPU_XSC3) || \
 	defined(CONFIG_CPU_XSCALE)
 #define PJ4(code...)
 #define XSC(code...)		code
 #else
 #error "Unsupported iWMMXt architecture"
 #endif

 #define MMX_WR0		 	(0x00)
 #define MMX_WR1		 	(0x08)
 #define MMX_WR2		 	(0x10)
 #define MMX_WR3			(0x18)
 #define MMX_WR4		 	(0x20)
 #define MMX_WR5		 	(0x28)
 #define MMX_WR6		 	(0x30)
 #define MMX_WR7		 	(0x38)
 #define MMX_WR8		 	(0x40)
 #define MMX_WR9		 	(0x48)
 #define MMX_WR10		(0x50)
 #define MMX_WR11		(0x58)
 #define MMX_WR12		(0x60)
 #define MMX_WR13		(0x68)
 #define MMX_WR14		(0x70)
 #define MMX_WR15		(0x78)
 #define MMX_WCSSF		(0x80)
 #define MMX_WCASF		(0x84)
 #define MMX_WCGR0		(0x88)
 #define MMX_WCGR1		(0x8C)
 #define MMX_WCGR2		(0x90)
 #define MMX_WCGR3		(0x94)

 #define MMX_SIZE		(0x98)

 	.text
 	.arm

 /*
  * Lazy switching of Concan coprocessor context
  *
  * r10 = struct thread_info pointer
  * r9  = ret_from_exception
  * lr  = undefined instr exit
  *
  * called from prefetch exception handler with interrupts enabled
  */

 ENTRY(iwmmxt_task_enable)
 	inc_preempt_count r10, r3

 	XSC(mrc	p15, 0, r2, c15, c1, 0)
 	PJ4(mrc p15, 0, r2, c1, c0, 2)
 	@ CP0 and CP1 accessible?
 	XSC(tst	r2, #0x3)
 	PJ4(tst	r2, #0xf)
 	bne	4f				@ if so no business here
 	@ enable access to CP0 and CP1
 	XSC(orr	r2, r2, #0x3)
 	XSC(mcr	p15, 0, r2, c15, c1, 0)
 	PJ4(orr	r2, r2, #0xf)
 	PJ4(mcr	p15, 0, r2, c1, c0, 2)

 	ldr	r3, =concan_owner
 	add	r0, r10, #TI_IWMMXT_STATE	@ get task Concan save area
 	ldr	r2, [sp, #60]			@ current task pc value
 	ldr	r1, [r3]			@ get current Concan owner
 	str	r0, [r3]			@ this task now owns Concan regs
 	sub	r2, r2, #4			@ adjust pc back
 	str	r2, [sp, #60]

 	mrc	p15, 0, r2, c2, c0, 0
 	mov	r2, r2				@ cpwait
 	bl	concan_save

 #ifdef CONFIG_PREEMPT_COUNT
 	get_thread_info r10
 #endif
 4:	dec_preempt_count r10, r3
 	ret	r9				@ normal exit from exception

 concan_save:

 	teq	r1, #0				@ test for last ownership
 	beq	concan_load			@ no owner, skip save

 	tmrc	r2, wCon

 	@ CUP? wCx
 	tst	r2, #0x1
 	beq 	1f

 concan_dump:

 	wstrw	wCSSF, r1, MMX_WCSSF
 	wstrw	wCASF, r1, MMX_WCASF
 	wstrw	wCGR0, r1, MMX_WCGR0
 	wstrw	wCGR1, r1, MMX_WCGR1
 	wstrw	wCGR2, r1, MMX_WCGR2
 	wstrw	wCGR3, r1, MMX_WCGR3

 1:	@ MUP? wRn
 	tst	r2, #0x2
 	beq	2f

 	wstrd	wR0,  r1, MMX_WR0
 	wstrd	wR1,  r1, MMX_WR1
 	wstrd	wR2,  r1, MMX_WR2
 	wstrd	wR3,  r1, MMX_WR3
 	wstrd	wR4,  r1, MMX_WR4
 	wstrd	wR5,  r1, MMX_WR5
 	wstrd	wR6,  r1, MMX_WR6
 	wstrd	wR7,  r1, MMX_WR7
 	wstrd	wR8,  r1, MMX_WR8
 	wstrd	wR9,  r1, MMX_WR9
 	wstrd	wR10, r1, MMX_WR10
 	wstrd	wR11, r1, MMX_WR11
 	wstrd	wR12, r1, MMX_WR12
 	wstrd	wR13, r1, MMX_WR13
 	wstrd	wR14, r1, MMX_WR14
 	wstrd	wR15, r1, MMX_WR15

 2:	teq	r0, #0				@ anything to load?
 	reteq	lr				@ if not, return

 concan_load:

 	@ Load wRn
 	wldrd	wR0,  r0, MMX_WR0
 	wldrd	wR1,  r0, MMX_WR1
 	wldrd	wR2,  r0, MMX_WR2
 	wldrd	wR3,  r0, MMX_WR3
 	wldrd	wR4,  r0, MMX_WR4
 	wldrd	wR5,  r0, MMX_WR5
 	wldrd	wR6,  r0, MMX_WR6
 	wldrd	wR7,  r0, MMX_WR7
 	wldrd	wR8,  r0, MMX_WR8
 	wldrd	wR9,  r0, MMX_WR9
 	wldrd	wR10, r0, MMX_WR10
 	wldrd	wR11, r0, MMX_WR11
 	wldrd	wR12, r0, MMX_WR12
 	wldrd	wR13, r0, MMX_WR13
 	wldrd	wR14, r0, MMX_WR14
 	wldrd	wR15, r0, MMX_WR15

 	@ Load wCx
 	wldrw	wCSSF, r0, MMX_WCSSF
 	wldrw	wCASF, r0, MMX_WCASF
 	wldrw	wCGR0, r0, MMX_WCGR0
 	wldrw	wCGR1, r0, MMX_WCGR1
 	wldrw	wCGR2, r0, MMX_WCGR2
 	wldrw	wCGR3, r0, MMX_WCGR3

 	@ clear CUP/MUP (only if r1 != 0)
 	teq	r1, #0
 	mov 	r2, #0
 	reteq	lr

 	tmcr	wCon, r2
 	ret	lr

 ENDPROC(iwmmxt_task_enable)

 /*
  * Back up Concan regs to save area and disable access to them
  * (mainly for gdb or sleep mode usage)
  *
  * r0 = struct thread_info pointer of target task or NULL for any
  */

 ENTRY(iwmmxt_task_disable)

 	stmfd	sp!, {r4, lr}

 	mrs	ip, cpsr
 	orr	r2, ip, #PSR_I_BIT		@ disable interrupts
 	msr	cpsr_c, r2

 	ldr	r3, =concan_owner
 	add	r2, r0, #TI_IWMMXT_STATE	@ get task Concan save area
 	ldr	r1, [r3]			@ get current Concan owner
 	teq	r1, #0				@ any current owner?
 	beq	1f				@ no: quit
 	teq	r0, #0				@ any owner?
 	teqne	r1, r2				@ or specified one?
 	bne	1f				@ no: quit

 	@ enable access to CP0 and CP1
 	XSC(mrc	p15, 0, r4, c15, c1, 0)
 	XSC(orr	r4, r4, #0x3)
 	XSC(mcr	p15, 0, r4, c15, c1, 0)
 	PJ4(mrc p15, 0, r4, c1, c0, 2)
 	PJ4(orr	r4, r4, #0xf)
 	PJ4(mcr	p15, 0, r4, c1, c0, 2)

 	mov	r0, #0				@ nothing to load
 	str	r0, [r3]			@ no more current owner
 	mrc	p15, 0, r2, c2, c0, 0
 	mov	r2, r2				@ cpwait
 	bl	concan_save

 	@ disable access to CP0 and CP1
 	XSC(bic	r4, r4, #0x3)
 	XSC(mcr	p15, 0, r4, c15, c1, 0)
 	PJ4(bic	r4, r4, #0xf)
 	PJ4(mcr	p15, 0, r4, c1, c0, 2)

 	mrc	p15, 0, r2, c2, c0, 0
 	mov	r2, r2				@ cpwait

 1:	msr	cpsr_c, ip			@ restore interrupt mode
 	ldmfd	sp!, {r4, pc}

 ENDPROC(iwmmxt_task_disable)

 /*
  * Copy Concan state to given memory address
  *
  * r0 = struct thread_info pointer of target task
  * r1 = memory address where to store Concan state
  *
  * this is called mainly in the creation of signal stack frames
  */

 ENTRY(iwmmxt_task_copy)

 	mrs	ip, cpsr
 	orr	r2, ip, #PSR_I_BIT		@ disable interrupts
 	msr	cpsr_c, r2

 	ldr	r3, =concan_owner
 	add	r2, r0, #TI_IWMMXT_STATE	@ get task Concan save area
 	ldr	r3, [r3]			@ get current Concan owner
 	teq	r2, r3				@ does this task own it...
 	beq	1f

 	@ current Concan values are in the task save area
 	msr	cpsr_c, ip			@ restore interrupt mode
 	mov	r0, r1
 	mov	r1, r2
 	mov	r2, #MMX_SIZE
 	b	memcpy

 1:	@ this task owns Concan regs -- grab a copy from there
 	mov	r0, #0				@ nothing to load
 	mov	r2, #3				@ save all regs
 	mov	r3, lr				@ preserve return address
 	bl	concan_dump
 	msr	cpsr_c, ip			@ restore interrupt mode
 	ret	r3

 ENDPROC(iwmmxt_task_copy)

 /*
  * Restore Concan state from given memory address
  *
  * r0 = struct thread_info pointer of target task
  * r1 = memory address where to get Concan state from
  *
  * this is used to restore Concan state when unwinding a signal stack frame
  */

 ENTRY(iwmmxt_task_restore)

 	mrs	ip, cpsr
 	orr	r2, ip, #PSR_I_BIT		@ disable interrupts
 	msr	cpsr_c, r2

 	ldr	r3, =concan_owner
 	add	r2, r0, #TI_IWMMXT_STATE	@ get task Concan save area
 	ldr	r3, [r3]			@ get current Concan owner
 	bic	r2, r2, #0x7			@ 64-bit alignment
 	teq	r2, r3				@ does this task own it...
 	beq	1f

 	@ this task doesn't own Concan regs -- use its save area
 	msr	cpsr_c, ip			@ restore interrupt mode
 	mov	r0, r2
 	mov	r2, #MMX_SIZE
 	b	memcpy

 1:	@ this task owns Concan regs -- load them directly
 	mov	r0, r1
 	mov	r1, #0				@ don't clear CUP/MUP
 	mov	r3, lr				@ preserve return address
 	bl	concan_load
 	msr	cpsr_c, ip			@ restore interrupt mode
 	ret	r3

 ENDPROC(iwmmxt_task_restore)

 /*
  * Concan handling on task switch
  *
  * r0 = next thread_info pointer
  *
  * Called only from the iwmmxt notifier with task preemption disabled.
  */
 ENTRY(iwmmxt_task_switch)

 	XSC(mrc	p15, 0, r1, c15, c1, 0)
 	PJ4(mrc	p15, 0, r1, c1, c0, 2)
 	@ CP0 and CP1 accessible?
 	XSC(tst	r1, #0x3)
 	PJ4(tst	r1, #0xf)
 	bne	1f				@ yes: block them for next task

 	ldr	r2, =concan_owner
 	add	r3, r0, #TI_IWMMXT_STATE	@ get next task Concan save area
 	ldr	r2, [r2]			@ get current Concan owner
 	teq	r2, r3				@ next task owns it?
 	retne	lr				@ no: leave Concan disabled

 1:	@ flip Concan access
 	XSC(eor	r1, r1, #0x3)
 	XSC(mcr	p15, 0, r1, c15, c1, 0)
 	PJ4(eor r1, r1, #0xf)
 	PJ4(mcr	p15, 0, r1, c1, c0, 2)

 	mrc	p15, 0, r1, c2, c0, 0
 	sub	pc, lr, r1, lsr #32		@ cpwait and return

 ENDPROC(iwmmxt_task_switch)

 /*
  * Remove Concan ownership of given task
  *
  * r0 = struct thread_info pointer
  */
 ENTRY(iwmmxt_task_release)

 	mrs	r2, cpsr
 	orr	ip, r2, #PSR_I_BIT		@ disable interrupts
 	msr	cpsr_c, ip
 	ldr	r3, =concan_owner
 	add	r0, r0, #TI_IWMMXT_STATE	@ get task Concan save area
 	ldr	r1, [r3]			@ get current Concan owner
 	eors	r0, r0, r1			@ if equal...
 	streq	r0, [r3]			@ then clear ownership
 	msr	cpsr_c, r2			@ restore interrupts
 	ret	lr

 ENDPROC(iwmmxt_task_release)

 	.data
 	.align	2
 concan_owner:
 	.word	0
	/* SPDX-License-Identifier: GPL-2.0-only */
	/*
	* linux/arch/arm/kernel/iwmmxt.S
	*
	* XScale iWMMXt (Concan) context switching and handling
	*
	* Initial code:
	* Copyright (c) 2003, Intel Corporation
	*
	* Full lazy switching support, optimizations and more, by Nicolas Pitre
	* Copyright (c) 2003-2004, MontaVista Software, Inc.
	*/

	#include <linux/linkage.h>
	#include <asm/ptrace.h>
	#include <asm/thread_info.h>
	#include <asm/asm-offsets.h>
	#include <asm/assembler.h>
	#include "iwmmxt.h"

	#if defined(CONFIG_CPU_PJ4) \|\| defined(CONFIG_CPU_PJ4B)
	#define PJ4(code...) code
	#define XSC(code...)
	#elif defined(CONFIG_CPU_MOHAWK) \|\| \
	defined(CONFIG_CPU_XSC3) \|\| \
	defined(CONFIG_CPU_XSCALE)
	#define PJ4(code...)
	#define XSC(code...) code
	#else
	#error "Unsupported iWMMXt architecture"
	#endif

	#define MMX_WR0 (0x00)
	#define MMX_WR1 (0x08)
	#define MMX_WR2 (0x10)
	#define MMX_WR3 (0x18)
	#define MMX_WR4 (0x20)
	#define MMX_WR5 (0x28)
	#define MMX_WR6 (0x30)
	#define MMX_WR7 (0x38)
	#define MMX_WR8 (0x40)
	#define MMX_WR9 (0x48)
	#define MMX_WR10 (0x50)
	#define MMX_WR11 (0x58)
	#define MMX_WR12 (0x60)
	#define MMX_WR13 (0x68)
	#define MMX_WR14 (0x70)
	#define MMX_WR15 (0x78)
	#define MMX_WCSSF (0x80)
	#define MMX_WCASF (0x84)
	#define MMX_WCGR0 (0x88)
	#define MMX_WCGR1 (0x8C)
	#define MMX_WCGR2 (0x90)
	#define MMX_WCGR3 (0x94)

	#define MMX_SIZE (0x98)

	.text
	.arm

	/*
	* Lazy switching of Concan coprocessor context
	*
	* r10 = struct thread_info pointer
	* r9 = ret_from_exception
	* lr = undefined instr exit
	*
	* called from prefetch exception handler with interrupts enabled
	*/

	ENTRY(iwmmxt_task_enable)
	inc_preempt_count r10, r3

	XSC(mrc p15, 0, r2, c15, c1, 0)
	PJ4(mrc p15, 0, r2, c1, c0, 2)
	@ CP0 and CP1 accessible?
	XSC(tst r2, #0x3)
	PJ4(tst r2, #0xf)
	bne 4f @ if so no business here
	@ enable access to CP0 and CP1
	XSC(orr r2, r2, #0x3)
	XSC(mcr p15, 0, r2, c15, c1, 0)
	PJ4(orr r2, r2, #0xf)
	PJ4(mcr p15, 0, r2, c1, c0, 2)

	ldr r3, =concan_owner
	add r0, r10, #TI_IWMMXT_STATE @ get task Concan save area
	ldr r2, [sp, #60] @ current task pc value
	ldr r1, [r3] @ get current Concan owner
	str r0, [r3] @ this task now owns Concan regs
	sub r2, r2, #4 @ adjust pc back
	str r2, [sp, #60]

	mrc p15, 0, r2, c2, c0, 0
	mov r2, r2 @ cpwait
	bl concan_save

	#ifdef CONFIG_PREEMPT_COUNT
	get_thread_info r10
	#endif
	4: dec_preempt_count r10, r3
	ret r9 @ normal exit from exception

	concan_save:

	teq r1, #0 @ test for last ownership
	beq concan_load @ no owner, skip save

	tmrc r2, wCon

	@ CUP? wCx
	tst r2, #0x1
	beq 1f

	concan_dump:

	wstrw wCSSF, r1, MMX_WCSSF
	wstrw wCASF, r1, MMX_WCASF
	wstrw wCGR0, r1, MMX_WCGR0
	wstrw wCGR1, r1, MMX_WCGR1
	wstrw wCGR2, r1, MMX_WCGR2
	wstrw wCGR3, r1, MMX_WCGR3

	1: @ MUP? wRn
	tst r2, #0x2
	beq 2f

	wstrd wR0, r1, MMX_WR0
	wstrd wR1, r1, MMX_WR1
	wstrd wR2, r1, MMX_WR2
	wstrd wR3, r1, MMX_WR3
	wstrd wR4, r1, MMX_WR4
	wstrd wR5, r1, MMX_WR5
	wstrd wR6, r1, MMX_WR6
	wstrd wR7, r1, MMX_WR7
	wstrd wR8, r1, MMX_WR8
	wstrd wR9, r1, MMX_WR9
	wstrd wR10, r1, MMX_WR10
	wstrd wR11, r1, MMX_WR11
	wstrd wR12, r1, MMX_WR12
	wstrd wR13, r1, MMX_WR13
	wstrd wR14, r1, MMX_WR14
	wstrd wR15, r1, MMX_WR15

	2: teq r0, #0 @ anything to load?
	reteq lr @ if not, return

	concan_load:

	@ Load wRn
	wldrd wR0, r0, MMX_WR0
	wldrd wR1, r0, MMX_WR1
	wldrd wR2, r0, MMX_WR2
	wldrd wR3, r0, MMX_WR3
	wldrd wR4, r0, MMX_WR4
	wldrd wR5, r0, MMX_WR5
	wldrd wR6, r0, MMX_WR6
	wldrd wR7, r0, MMX_WR7
	wldrd wR8, r0, MMX_WR8
	wldrd wR9, r0, MMX_WR9
	wldrd wR10, r0, MMX_WR10
	wldrd wR11, r0, MMX_WR11
	wldrd wR12, r0, MMX_WR12
	wldrd wR13, r0, MMX_WR13
	wldrd wR14, r0, MMX_WR14
	wldrd wR15, r0, MMX_WR15

	@ Load wCx
	wldrw wCSSF, r0, MMX_WCSSF
	wldrw wCASF, r0, MMX_WCASF
	wldrw wCGR0, r0, MMX_WCGR0
	wldrw wCGR1, r0, MMX_WCGR1
	wldrw wCGR2, r0, MMX_WCGR2
	wldrw wCGR3, r0, MMX_WCGR3

	@ clear CUP/MUP (only if r1 != 0)
	teq r1, #0
	mov r2, #0
	reteq lr

	tmcr wCon, r2
	ret lr

	ENDPROC(iwmmxt_task_enable)

	/*
	* Back up Concan regs to save area and disable access to them
	* (mainly for gdb or sleep mode usage)
	*
	* r0 = struct thread_info pointer of target task or NULL for any
	*/

	ENTRY(iwmmxt_task_disable)

	stmfd sp!, {r4, lr}

	mrs ip, cpsr
	orr r2, ip, #PSR_I_BIT @ disable interrupts
	msr cpsr_c, r2

	ldr r3, =concan_owner
	add r2, r0, #TI_IWMMXT_STATE @ get task Concan save area
	ldr r1, [r3] @ get current Concan owner
	teq r1, #0 @ any current owner?
	beq 1f @ no: quit
	teq r0, #0 @ any owner?
	teqne r1, r2 @ or specified one?
	bne 1f @ no: quit

	@ enable access to CP0 and CP1
	XSC(mrc p15, 0, r4, c15, c1, 0)
	XSC(orr r4, r4, #0x3)
	XSC(mcr p15, 0, r4, c15, c1, 0)
	PJ4(mrc p15, 0, r4, c1, c0, 2)
	PJ4(orr r4, r4, #0xf)
	PJ4(mcr p15, 0, r4, c1, c0, 2)

	mov r0, #0 @ nothing to load
	str r0, [r3] @ no more current owner
	mrc p15, 0, r2, c2, c0, 0
	mov r2, r2 @ cpwait
	bl concan_save

	@ disable access to CP0 and CP1
	XSC(bic r4, r4, #0x3)
	XSC(mcr p15, 0, r4, c15, c1, 0)
	PJ4(bic r4, r4, #0xf)
	PJ4(mcr p15, 0, r4, c1, c0, 2)

	mrc p15, 0, r2, c2, c0, 0
	mov r2, r2 @ cpwait

	1: msr cpsr_c, ip @ restore interrupt mode
	ldmfd sp!, {r4, pc}

	ENDPROC(iwmmxt_task_disable)

	/*
	* Copy Concan state to given memory address
	*
	* r0 = struct thread_info pointer of target task
	* r1 = memory address where to store Concan state
	*
	* this is called mainly in the creation of signal stack frames
	*/

	ENTRY(iwmmxt_task_copy)

	mrs ip, cpsr
	orr r2, ip, #PSR_I_BIT @ disable interrupts
	msr cpsr_c, r2

	ldr r3, =concan_owner
	add r2, r0, #TI_IWMMXT_STATE @ get task Concan save area
	ldr r3, [r3] @ get current Concan owner
	teq r2, r3 @ does this task own it...
	beq 1f

	@ current Concan values are in the task save area
	msr cpsr_c, ip @ restore interrupt mode
	mov r0, r1
	mov r1, r2
	mov r2, #MMX_SIZE
	b memcpy

	1: @ this task owns Concan regs -- grab a copy from there
	mov r0, #0 @ nothing to load
	mov r2, #3 @ save all regs
	mov r3, lr @ preserve return address
	bl concan_dump
	msr cpsr_c, ip @ restore interrupt mode
	ret r3

	ENDPROC(iwmmxt_task_copy)

	/*
	* Restore Concan state from given memory address
	*
	* r0 = struct thread_info pointer of target task
	* r1 = memory address where to get Concan state from
	*
	* this is used to restore Concan state when unwinding a signal stack frame
	*/

	ENTRY(iwmmxt_task_restore)

	mrs ip, cpsr
	orr r2, ip, #PSR_I_BIT @ disable interrupts
	msr cpsr_c, r2

	ldr r3, =concan_owner
	add r2, r0, #TI_IWMMXT_STATE @ get task Concan save area
	ldr r3, [r3] @ get current Concan owner
	bic r2, r2, #0x7 @ 64-bit alignment
	teq r2, r3 @ does this task own it...
	beq 1f

	@ this task doesn't own Concan regs -- use its save area
	msr cpsr_c, ip @ restore interrupt mode
	mov r0, r2
	mov r2, #MMX_SIZE
	b memcpy

	1: @ this task owns Concan regs -- load them directly
	mov r0, r1
	mov r1, #0 @ don't clear CUP/MUP
	mov r3, lr @ preserve return address
	bl concan_load
	msr cpsr_c, ip @ restore interrupt mode
	ret r3

	ENDPROC(iwmmxt_task_restore)

	/*
	* Concan handling on task switch
	*
	* r0 = next thread_info pointer
	*
	* Called only from the iwmmxt notifier with task preemption disabled.
	*/
	ENTRY(iwmmxt_task_switch)

	XSC(mrc p15, 0, r1, c15, c1, 0)
	PJ4(mrc p15, 0, r1, c1, c0, 2)
	@ CP0 and CP1 accessible?
	XSC(tst r1, #0x3)
	PJ4(tst r1, #0xf)
	bne 1f @ yes: block them for next task

	ldr r2, =concan_owner
	add r3, r0, #TI_IWMMXT_STATE @ get next task Concan save area
	ldr r2, [r2] @ get current Concan owner
	teq r2, r3 @ next task owns it?
	retne lr @ no: leave Concan disabled

	1: @ flip Concan access
	XSC(eor r1, r1, #0x3)
	XSC(mcr p15, 0, r1, c15, c1, 0)
	PJ4(eor r1, r1, #0xf)
	PJ4(mcr p15, 0, r1, c1, c0, 2)

	mrc p15, 0, r1, c2, c0, 0
	sub pc, lr, r1, lsr #32 @ cpwait and return

	ENDPROC(iwmmxt_task_switch)

	/*
	* Remove Concan ownership of given task
	*
	* r0 = struct thread_info pointer
	*/
	ENTRY(iwmmxt_task_release)

	mrs r2, cpsr
	orr ip, r2, #PSR_I_BIT @ disable interrupts
	msr cpsr_c, ip
	ldr r3, =concan_owner
	add r0, r0, #TI_IWMMXT_STATE @ get task Concan save area
	ldr r1, [r3] @ get current Concan owner
	eors r0, r0, r1 @ if equal...
	streq r0, [r3] @ then clear ownership
	msr cpsr_c, r2 @ restore interrupts
	ret lr

	ENDPROC(iwmmxt_task_release)

	.data
	.align 2
	concan_owner:
	.word 0