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82 lines
2.4 KiB
82 lines
2.4 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* fpu.c - save/restore of Floating Point Unit Registers on task switch |
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* |
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) |
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*/ |
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#include <linux/sched.h> |
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#include <asm/fpu.h> |
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#ifdef CONFIG_ISA_ARCOMPACT |
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/* |
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* To save/restore FPU regs, simplest scheme would use LR/SR insns. |
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* However since SR serializes the pipeline, an alternate "hack" can be used |
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* which uses the FPU Exchange insn (DEXCL) to r/w FPU regs. |
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* |
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* Store to 64bit dpfp1 reg from a pair of core regs: |
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* dexcl1 0, r1, r0 ; where r1:r0 is the 64 bit val |
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* |
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* Read from dpfp1 into pair of core regs (w/o clobbering dpfp1) |
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* mov_s r3, 0 |
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* daddh11 r1, r3, r3 ; get "hi" into r1 (dpfp1 unchanged) |
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* dexcl1 r0, r1, r3 ; get "low" into r0 (dpfp1 low clobbered) |
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* dexcl1 0, r1, r0 ; restore dpfp1 to orig value |
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* |
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* However we can tweak the read, so that read-out of outgoing task's FPU regs |
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* and write of incoming task's regs happen in one shot. So all the work is |
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* done before context switch |
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*/ |
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void fpu_save_restore(struct task_struct *prev, struct task_struct *next) |
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{ |
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unsigned int *saveto = &prev->thread.fpu.aux_dpfp[0].l; |
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unsigned int *readfrom = &next->thread.fpu.aux_dpfp[0].l; |
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const unsigned int zero = 0; |
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__asm__ __volatile__( |
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"daddh11 %0, %2, %2\n" |
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"dexcl1 %1, %3, %4\n" |
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: "=&r" (*(saveto + 1)), /* early clobber must here */ |
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"=&r" (*(saveto)) |
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: "r" (zero), "r" (*(readfrom + 1)), "r" (*(readfrom)) |
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); |
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__asm__ __volatile__( |
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"daddh22 %0, %2, %2\n" |
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"dexcl2 %1, %3, %4\n" |
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: "=&r"(*(saveto + 3)), /* early clobber must here */ |
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"=&r"(*(saveto + 2)) |
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: "r" (zero), "r" (*(readfrom + 3)), "r" (*(readfrom + 2)) |
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); |
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} |
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#else |
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void fpu_init_task(struct pt_regs *regs) |
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{ |
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const unsigned int fwe = 0x80000000; |
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/* default rounding mode */ |
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write_aux_reg(ARC_REG_FPU_CTRL, 0x100); |
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/* Initialize to zero: setting requires FWE be set */ |
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write_aux_reg(ARC_REG_FPU_STATUS, fwe); |
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} |
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void fpu_save_restore(struct task_struct *prev, struct task_struct *next) |
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{ |
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struct arc_fpu *save = &prev->thread.fpu; |
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struct arc_fpu *restore = &next->thread.fpu; |
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const unsigned int fwe = 0x80000000; |
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save->ctrl = read_aux_reg(ARC_REG_FPU_CTRL); |
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save->status = read_aux_reg(ARC_REG_FPU_STATUS); |
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write_aux_reg(ARC_REG_FPU_CTRL, restore->ctrl); |
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write_aux_reg(ARC_REG_FPU_STATUS, (fwe | restore->status)); |
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} |
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#endif
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