xref: /openbmc/linux/arch/loongarch/kernel/kfpu.c (revision 2478e4b7)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2023 Loongson Technology Corporation Limited
4  */
5 
6 #include <linux/cpu.h>
7 #include <linux/init.h>
8 #include <asm/fpu.h>
9 #include <asm/smp.h>
10 
11 static unsigned int euen_mask = CSR_EUEN_FPEN;
12 
13 /*
14  * The critical section between kernel_fpu_begin() and kernel_fpu_end()
15  * is non-reentrant. It is the caller's responsibility to avoid reentrance.
16  * See drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c as an example.
17  */
18 static DEFINE_PER_CPU(bool, in_kernel_fpu);
19 static DEFINE_PER_CPU(unsigned int, euen_current);
20 
kernel_fpu_begin(void)21 void kernel_fpu_begin(void)
22 {
23 	unsigned int *euen_curr;
24 
25 	preempt_disable();
26 
27 	WARN_ON(this_cpu_read(in_kernel_fpu));
28 
29 	this_cpu_write(in_kernel_fpu, true);
30 	euen_curr = this_cpu_ptr(&euen_current);
31 
32 	*euen_curr = csr_xchg32(euen_mask, euen_mask, LOONGARCH_CSR_EUEN);
33 
34 #ifdef CONFIG_CPU_HAS_LASX
35 	if (*euen_curr & CSR_EUEN_LASXEN)
36 		_save_lasx(&current->thread.fpu);
37 	else
38 #endif
39 #ifdef CONFIG_CPU_HAS_LSX
40 	if (*euen_curr & CSR_EUEN_LSXEN)
41 		_save_lsx(&current->thread.fpu);
42 	else
43 #endif
44 	if (*euen_curr & CSR_EUEN_FPEN)
45 		_save_fp(&current->thread.fpu);
46 
47 	write_fcsr(LOONGARCH_FCSR0, 0);
48 }
49 EXPORT_SYMBOL_GPL(kernel_fpu_begin);
50 
kernel_fpu_end(void)51 void kernel_fpu_end(void)
52 {
53 	unsigned int *euen_curr;
54 
55 	WARN_ON(!this_cpu_read(in_kernel_fpu));
56 
57 	euen_curr = this_cpu_ptr(&euen_current);
58 
59 #ifdef CONFIG_CPU_HAS_LASX
60 	if (*euen_curr & CSR_EUEN_LASXEN)
61 		_restore_lasx(&current->thread.fpu);
62 	else
63 #endif
64 #ifdef CONFIG_CPU_HAS_LSX
65 	if (*euen_curr & CSR_EUEN_LSXEN)
66 		_restore_lsx(&current->thread.fpu);
67 	else
68 #endif
69 	if (*euen_curr & CSR_EUEN_FPEN)
70 		_restore_fp(&current->thread.fpu);
71 
72 	*euen_curr = csr_xchg32(*euen_curr, euen_mask, LOONGARCH_CSR_EUEN);
73 
74 	this_cpu_write(in_kernel_fpu, false);
75 
76 	preempt_enable();
77 }
78 EXPORT_SYMBOL_GPL(kernel_fpu_end);
79 
init_euen_mask(void)80 static int __init init_euen_mask(void)
81 {
82 	if (cpu_has_lsx)
83 		euen_mask |= CSR_EUEN_LSXEN;
84 
85 	if (cpu_has_lasx)
86 		euen_mask |= CSR_EUEN_LASXEN;
87 
88 	return 0;
89 }
90 arch_initcall(init_euen_mask);
91