xref: /openbmc/linux/arch/mips/include/asm/fpu.h (revision 0661cb2a)
1 /* SPDX-License-Identifier: GPL-2.0-or-later */
2 /*
3  * Copyright (C) 2002 MontaVista Software Inc.
4  * Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
5  */
6 #ifndef _ASM_FPU_H
7 #define _ASM_FPU_H
8 
9 #include <linux/sched.h>
10 #include <linux/sched/task_stack.h>
11 #include <linux/ptrace.h>
12 #include <linux/thread_info.h>
13 #include <linux/bitops.h>
14 
15 #include <asm/mipsregs.h>
16 #include <asm/cpu.h>
17 #include <asm/cpu-features.h>
18 #include <asm/fpu_emulator.h>
19 #include <asm/hazards.h>
20 #include <asm/ptrace.h>
21 #include <asm/processor.h>
22 #include <asm/current.h>
23 #include <asm/msa.h>
24 
25 #ifdef CONFIG_MIPS_MT_FPAFF
26 #include <asm/mips_mt.h>
27 #endif
28 
29 /*
30  * This enum specifies a mode in which we want the FPU to operate, for cores
31  * which implement the Status.FR bit. Note that the bottom bit of the value
32  * purposefully matches the desired value of the Status.FR bit.
33  */
34 enum fpu_mode {
35 	FPU_32BIT = 0,		/* FR = 0 */
36 	FPU_64BIT,		/* FR = 1, FRE = 0 */
37 	FPU_AS_IS,
38 	FPU_HYBRID,		/* FR = 1, FRE = 1 */
39 
40 #define FPU_FR_MASK		0x1
41 };
42 
43 #ifdef CONFIG_MIPS_FP_SUPPORT
44 
45 extern void _save_fp(struct task_struct *);
46 extern void _restore_fp(struct task_struct *);
47 
48 #define __disable_fpu()							\
49 do {									\
50 	clear_c0_status(ST0_CU1);					\
51 	disable_fpu_hazard();						\
52 } while (0)
53 
54 static inline int __enable_fpu(enum fpu_mode mode)
55 {
56 	int fr;
57 
58 	switch (mode) {
59 	case FPU_AS_IS:
60 		/* just enable the FPU in its current mode */
61 		set_c0_status(ST0_CU1);
62 		enable_fpu_hazard();
63 		return 0;
64 
65 	case FPU_HYBRID:
66 		if (!cpu_has_fre)
67 			return SIGFPE;
68 
69 		/* set FRE */
70 		set_c0_config5(MIPS_CONF5_FRE);
71 		goto fr_common;
72 
73 	case FPU_64BIT:
74 #if !(defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_CPU_MIPSR5) || \
75       defined(CONFIG_CPU_MIPSR6) || defined(CONFIG_64BIT))
76 		/* we only have a 32-bit FPU */
77 		return SIGFPE;
78 #endif
79 		/* fallthrough */
80 	case FPU_32BIT:
81 		if (cpu_has_fre) {
82 			/* clear FRE */
83 			clear_c0_config5(MIPS_CONF5_FRE);
84 		}
85 fr_common:
86 		/* set CU1 & change FR appropriately */
87 		fr = (int)mode & FPU_FR_MASK;
88 		change_c0_status(ST0_CU1 | ST0_FR, ST0_CU1 | (fr ? ST0_FR : 0));
89 		enable_fpu_hazard();
90 
91 		/* check FR has the desired value */
92 		if (!!(read_c0_status() & ST0_FR) == !!fr)
93 			return 0;
94 
95 		/* unsupported FR value */
96 		__disable_fpu();
97 		return SIGFPE;
98 
99 	default:
100 		BUG();
101 	}
102 
103 	return SIGFPE;
104 }
105 
106 #define clear_fpu_owner()	clear_thread_flag(TIF_USEDFPU)
107 
108 static inline int __is_fpu_owner(void)
109 {
110 	return test_thread_flag(TIF_USEDFPU);
111 }
112 
113 static inline int is_fpu_owner(void)
114 {
115 	return cpu_has_fpu && __is_fpu_owner();
116 }
117 
118 static inline int __own_fpu(void)
119 {
120 	enum fpu_mode mode;
121 	int ret;
122 
123 	if (test_thread_flag(TIF_HYBRID_FPREGS))
124 		mode = FPU_HYBRID;
125 	else
126 		mode = !test_thread_flag(TIF_32BIT_FPREGS);
127 
128 	ret = __enable_fpu(mode);
129 	if (ret)
130 		return ret;
131 
132 	KSTK_STATUS(current) |= ST0_CU1;
133 	if (mode == FPU_64BIT || mode == FPU_HYBRID)
134 		KSTK_STATUS(current) |= ST0_FR;
135 	else /* mode == FPU_32BIT */
136 		KSTK_STATUS(current) &= ~ST0_FR;
137 
138 	set_thread_flag(TIF_USEDFPU);
139 	return 0;
140 }
141 
142 static inline int own_fpu_inatomic(int restore)
143 {
144 	int ret = 0;
145 
146 	if (cpu_has_fpu && !__is_fpu_owner()) {
147 		ret = __own_fpu();
148 		if (restore && !ret)
149 			_restore_fp(current);
150 	}
151 	return ret;
152 }
153 
154 static inline int own_fpu(int restore)
155 {
156 	int ret;
157 
158 	preempt_disable();
159 	ret = own_fpu_inatomic(restore);
160 	preempt_enable();
161 	return ret;
162 }
163 
164 static inline void lose_fpu_inatomic(int save, struct task_struct *tsk)
165 {
166 	if (is_msa_enabled()) {
167 		if (save) {
168 			save_msa(tsk);
169 			tsk->thread.fpu.fcr31 =
170 					read_32bit_cp1_register(CP1_STATUS);
171 		}
172 		disable_msa();
173 		clear_tsk_thread_flag(tsk, TIF_USEDMSA);
174 		__disable_fpu();
175 	} else if (is_fpu_owner()) {
176 		if (save)
177 			_save_fp(tsk);
178 		__disable_fpu();
179 	} else {
180 		/* FPU should not have been left enabled with no owner */
181 		WARN(read_c0_status() & ST0_CU1,
182 		     "Orphaned FPU left enabled");
183 	}
184 	KSTK_STATUS(tsk) &= ~ST0_CU1;
185 	clear_tsk_thread_flag(tsk, TIF_USEDFPU);
186 }
187 
188 static inline void lose_fpu(int save)
189 {
190 	preempt_disable();
191 	lose_fpu_inatomic(save, current);
192 	preempt_enable();
193 }
194 
195 /**
196  * init_fp_ctx() - Initialize task FP context
197  * @target: The task whose FP context should be initialized.
198  *
199  * Initializes the FP context of the target task to sane default values if that
200  * target task does not already have valid FP context. Once the context has
201  * been initialized, the task will be marked as having used FP & thus having
202  * valid FP context.
203  *
204  * Returns: true if context is initialized, else false.
205  */
206 static inline bool init_fp_ctx(struct task_struct *target)
207 {
208 	/* If FP has been used then the target already has context */
209 	if (tsk_used_math(target))
210 		return false;
211 
212 	/* Begin with data registers set to all 1s... */
213 	memset(&target->thread.fpu.fpr, ~0, sizeof(target->thread.fpu.fpr));
214 
215 	/* FCSR has been preset by `mips_set_personality_nan'.  */
216 
217 	/*
218 	 * Record that the target has "used" math, such that the context
219 	 * just initialised, and any modifications made by the caller,
220 	 * aren't discarded.
221 	 */
222 	set_stopped_child_used_math(target);
223 
224 	return true;
225 }
226 
227 static inline void save_fp(struct task_struct *tsk)
228 {
229 	if (cpu_has_fpu)
230 		_save_fp(tsk);
231 }
232 
233 static inline void restore_fp(struct task_struct *tsk)
234 {
235 	if (cpu_has_fpu)
236 		_restore_fp(tsk);
237 }
238 
239 static inline union fpureg *get_fpu_regs(struct task_struct *tsk)
240 {
241 	if (tsk == current) {
242 		preempt_disable();
243 		if (is_fpu_owner())
244 			_save_fp(current);
245 		preempt_enable();
246 	}
247 
248 	return tsk->thread.fpu.fpr;
249 }
250 
251 #else /* !CONFIG_MIPS_FP_SUPPORT */
252 
253 /*
254  * When FP support is disabled we provide only a minimal set of stub functions
255  * to avoid callers needing to care too much about CONFIG_MIPS_FP_SUPPORT.
256  */
257 
258 static inline int __enable_fpu(enum fpu_mode mode)
259 {
260 	return SIGILL;
261 }
262 
263 static inline void __disable_fpu(void)
264 {
265 	/* no-op */
266 }
267 
268 
269 static inline int is_fpu_owner(void)
270 {
271 	return 0;
272 }
273 
274 static inline void clear_fpu_owner(void)
275 {
276 	/* no-op */
277 }
278 
279 static inline int own_fpu_inatomic(int restore)
280 {
281 	return SIGILL;
282 }
283 
284 static inline int own_fpu(int restore)
285 {
286 	return SIGILL;
287 }
288 
289 static inline void lose_fpu_inatomic(int save, struct task_struct *tsk)
290 {
291 	/* no-op */
292 }
293 
294 static inline void lose_fpu(int save)
295 {
296 	/* no-op */
297 }
298 
299 static inline bool init_fp_ctx(struct task_struct *target)
300 {
301 	return false;
302 }
303 
304 /*
305  * The following functions should only be called in paths where we know that FP
306  * support is enabled, typically a path where own_fpu() or __enable_fpu() have
307  * returned successfully. When CONFIG_MIPS_FP_SUPPORT=n it is known at compile
308  * time that this should never happen, so calls to these functions should be
309  * optimized away & never actually be emitted.
310  */
311 
312 extern void save_fp(struct task_struct *tsk)
313 	__compiletime_error("save_fp() should not be called when CONFIG_MIPS_FP_SUPPORT=n");
314 
315 extern void _save_fp(struct task_struct *)
316 	__compiletime_error("_save_fp() should not be called when CONFIG_MIPS_FP_SUPPORT=n");
317 
318 extern void restore_fp(struct task_struct *tsk)
319 	__compiletime_error("restore_fp() should not be called when CONFIG_MIPS_FP_SUPPORT=n");
320 
321 extern void _restore_fp(struct task_struct *)
322 	__compiletime_error("_restore_fp() should not be called when CONFIG_MIPS_FP_SUPPORT=n");
323 
324 extern union fpureg *get_fpu_regs(struct task_struct *tsk)
325 	__compiletime_error("get_fpu_regs() should not be called when CONFIG_MIPS_FP_SUPPORT=n");
326 
327 #endif /* !CONFIG_MIPS_FP_SUPPORT */
328 #endif /* _ASM_FPU_H */
329