/* * fpu.c - save/restore of Floating Point Unit Registers on task switch * * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #include <linux/sched.h>#include <asm/switch_to.h> /* * To save/restore FPU regs, simplest scheme would use LR/SR insns. * However since SR serializes the pipeline, an alternate "hack" can be used * which uses the FPU Exchange insn (DEXCL) to r/w FPU regs. * * Store to 64bit dpfp1 reg from a pair of core regs: *   dexcl1 0, r1, r0  ; where r1:r0 is the 64 bit val * * Read from dpfp1 into pair of core regs (w/o clobbering dpfp1) *   mov_s    r3, 0 *   daddh11  r1, r3, r3   ; get "hi" into r1 (dpfp1 unchanged) *   dexcl1   r0, r1, r3   ; get "low" into r0 (dpfp1 low clobbered) *   dexcl1    0, r1, r0   ; restore dpfp1 to orig value * * However we can tweak the read, so that read-out of outgoing task's FPU regs * and write of incoming task's regs happen in one shot. So all the work is * done before context switch */ void fpu_save_restore(struct task_struct *prev, struct task_struct *next){	unsigned int *saveto = &prev->thread.fpu.aux_dpfp[0].l;	unsigned int *readfrom = &next->thread.fpu.aux_dpfp[0].l; 	const unsigned int zero = 0; 	__asm__ __volatile__(		"daddh11  %0, %2, %2\n"		"dexcl1   %1, %3, %4\n"		: "=&r" (*(saveto + 1)), /* early clobber must here */		  "=&r" (*(saveto))		: "r" (zero), "r" (*(readfrom + 1)), "r" (*(readfrom))	); 	__asm__ __volatile__(		"daddh22  %0, %2, %2\n"		"dexcl2   %1, %3, %4\n"		: "=&r"(*(saveto + 3)),	/* early clobber must here */		  "=&r"(*(saveto + 2))		: "r" (zero), "r" (*(readfrom + 3)), "r" (*(readfrom + 2))	);}