xref: /openbmc/linux/arch/xtensa/kernel/coprocessor.S (revision 48ca54e3) 
1/*
2 * arch/xtensa/kernel/coprocessor.S
3 *
4 * Xtensa processor configuration-specific table of coprocessor and
5 * other custom register layout information.
6 *
7 * This file is subject to the terms and conditions of the GNU General Public
8 * License.  See the file "COPYING" in the main directory of this archive
9 * for more details.
10 *
11 * Copyright (C) 2003 - 2007 Tensilica Inc.
12 */
13
14
15#include <linux/linkage.h>
16#include <asm/asm-offsets.h>
17#include <asm/asmmacro.h>
18#include <asm/coprocessor.h>
19#include <asm/current.h>
20#include <asm/regs.h>
21
22/*
23 * Rules for coprocessor state manipulation on SMP:
24 *
25 * - a task may have live coprocessors only on one CPU.
26 *
27 * - whether coprocessor context of task T is live on some CPU is
28 *   denoted by T's thread_info->cpenable.
29 *
30 * - non-zero thread_info->cpenable means that thread_info->cp_owner_cpu
31 *   is valid in the T's thread_info. Zero thread_info->cpenable means that
32 *   coprocessor context is valid in the T's thread_info.
33 *
34 * - if a coprocessor context of task T is live on CPU X, only CPU X changes
35 *   T's thread_info->cpenable, cp_owner_cpu and coprocessor save area.
36 *   This is done by making sure that for the task T with live coprocessor
37 *   on CPU X cpenable SR is 0 when T runs on any other CPU Y.
38 *   When fast_coprocessor exception is taken on CPU Y it goes to the
39 *   C-level do_coprocessor that uses IPI to make CPU X flush T's coprocessors.
40 */
41
42#if XTENSA_HAVE_COPROCESSORS
43
44/*
45 * Macros for lazy context switch.
46 */
47
48#define SAVE_CP_REGS(x)							\
49	.if XTENSA_HAVE_COPROCESSOR(x);					\
50		.align 4;						\
51	.Lsave_cp_regs_cp##x:						\
52		xchal_cp##x##_store a2 a3 a4 a5 a6;			\
53		ret;							\
54	.endif
55
56#define LOAD_CP_REGS(x)							\
57	.if XTENSA_HAVE_COPROCESSOR(x);					\
58		.align 4;						\
59	.Lload_cp_regs_cp##x:						\
60		xchal_cp##x##_load a2 a3 a4 a5 a6;			\
61		ret;							\
62	.endif
63
64#define CP_REGS_TAB(x)							\
65	.if XTENSA_HAVE_COPROCESSOR(x);					\
66		.long .Lsave_cp_regs_cp##x;				\
67		.long .Lload_cp_regs_cp##x;				\
68	.else;								\
69		.long 0, 0;						\
70	.endif;								\
71	.long THREAD_XTREGS_CP##x
72
73#define CP_REGS_TAB_SAVE 0
74#define CP_REGS_TAB_LOAD 4
75#define CP_REGS_TAB_OFFSET 8
76
77	__XTENSA_HANDLER
78
79	SAVE_CP_REGS(0)
80	SAVE_CP_REGS(1)
81	SAVE_CP_REGS(2)
82	SAVE_CP_REGS(3)
83	SAVE_CP_REGS(4)
84	SAVE_CP_REGS(5)
85	SAVE_CP_REGS(6)
86	SAVE_CP_REGS(7)
87
88	LOAD_CP_REGS(0)
89	LOAD_CP_REGS(1)
90	LOAD_CP_REGS(2)
91	LOAD_CP_REGS(3)
92	LOAD_CP_REGS(4)
93	LOAD_CP_REGS(5)
94	LOAD_CP_REGS(6)
95	LOAD_CP_REGS(7)
96
97	.align 4
98.Lcp_regs_jump_table:
99	CP_REGS_TAB(0)
100	CP_REGS_TAB(1)
101	CP_REGS_TAB(2)
102	CP_REGS_TAB(3)
103	CP_REGS_TAB(4)
104	CP_REGS_TAB(5)
105	CP_REGS_TAB(6)
106	CP_REGS_TAB(7)
107
108/*
109 * Entry condition:
110 *
111 *   a0:	trashed, original value saved on stack (PT_AREG0)
112 *   a1:	a1
113 *   a2:	new stack pointer, original in DEPC
114 *   a3:	a3
115 *   depc:	a2, original value saved on stack (PT_DEPC)
116 *   excsave_1:	dispatch table
117 *
118 *   PT_DEPC >= VALID_DOUBLE_EXCEPTION_ADDRESS: double exception, DEPC
119 *	     <  VALID_DOUBLE_EXCEPTION_ADDRESS: regular exception
120 */
121
122ENTRY(fast_coprocessor)
123
124	s32i	a3, a2, PT_AREG3
125
126#ifdef CONFIG_SMP
127	/*
128	 * Check if any coprocessor context is live on another CPU
129	 * and if so go through the C-level coprocessor exception handler
130	 * to flush it to memory.
131	 */
132	GET_THREAD_INFO (a0, a2)
133	l32i	a3, a0, THREAD_CPENABLE
134	beqz	a3, .Lload_local
135
136	/*
137	 * Pairs with smp_wmb in local_coprocessor_release_all
138	 * and with both memws below.
139	 */
140	memw
141	l32i	a3, a0, THREAD_CPU
142	l32i	a0, a0, THREAD_CP_OWNER_CPU
143	beq	a0, a3, .Lload_local
144
145	rsr	a0, ps
146	l32i	a3, a2, PT_AREG3
147	bbci.l	a0, PS_UM_BIT, 1f
148	call0	user_exception
1491:	call0	kernel_exception
150#endif
151
152	/* Save remaining registers a1-a3 and SAR */
153
154.Lload_local:
155	rsr	a3, sar
156	s32i	a1, a2, PT_AREG1
157	s32i	a3, a2, PT_SAR
158	mov	a1, a2
159	rsr	a2, depc
160	s32i	a2, a1, PT_AREG2
161
162	/* The hal macros require up to 4 temporary registers. We use a3..a6. */
163
164	s32i	a4, a1, PT_AREG4
165	s32i	a5, a1, PT_AREG5
166	s32i	a6, a1, PT_AREG6
167	s32i	a7, a1, PT_AREG7
168	s32i	a8, a1, PT_AREG8
169	s32i	a9, a1, PT_AREG9
170	s32i	a10, a1, PT_AREG10
171
172	/* Find coprocessor number. Subtract first CP EXCCAUSE from EXCCAUSE */
173
174	rsr	a3, exccause
175	addi	a3, a3, -EXCCAUSE_COPROCESSOR0_DISABLED
176
177	/* Set corresponding CPENABLE bit -> (sar:cp-index, a3: 1<<cp-index)*/
178
179	ssl	a3			# SAR: 32 - coprocessor_number
180	movi	a2, 1
181	rsr	a0, cpenable
182	sll	a2, a2
183	or	a0, a0, a2
184	wsr	a0, cpenable
185	rsync
186
187	/* Get coprocessor save/load table entry (a7). */
188
189	movi	a7, .Lcp_regs_jump_table
190	addx8	a7, a3, a7
191	addx4	a7, a3, a7
192
193	/* Retrieve previous owner (a8). */
194
195	rsr	a0, excsave1		# exc_table
196	addx4	a0, a3, a0		# entry for CP
197	l32i	a8, a0, EXC_TABLE_COPROCESSOR_OWNER
198
199	/* Set new owner (a9). */
200
201	GET_THREAD_INFO (a9, a1)
202	l32i	a4, a9, THREAD_CPU
203	s32i	a9, a0, EXC_TABLE_COPROCESSOR_OWNER
204	s32i	a4, a9, THREAD_CP_OWNER_CPU
205
206	/*
207	 * Enable coprocessor for the new owner. (a2 = 1 << CP number)
208	 * This can be done before loading context into the coprocessor.
209	 */
210	l32i	a4, a9, THREAD_CPENABLE
211	or	a4, a4, a2
212
213	/*
214	 * Make sure THREAD_CP_OWNER_CPU is in memory before updating
215	 * THREAD_CPENABLE
216	 */
217	memw				# (2)
218	s32i	a4, a9, THREAD_CPENABLE
219
220	beqz	a8, 1f			# skip 'save' if no previous owner
221
222	/* Disable coprocessor for previous owner. (a2 = 1 << CP number) */
223
224	l32i	a10, a8, THREAD_CPENABLE
225	xor	a10, a10, a2
226
227	/* Get context save area and call save routine. */
228
229	l32i	a2, a7, CP_REGS_TAB_OFFSET
230	l32i	a3, a7, CP_REGS_TAB_SAVE
231	add	a2, a2, a8
232	callx0	a3
233
234	/*
235	 * Make sure coprocessor context and THREAD_CP_OWNER_CPU are in memory
236	 * before updating THREAD_CPENABLE
237	 */
238	memw				# (3)
239	s32i	a10, a8, THREAD_CPENABLE
2401:
241	/* Get context save area and call load routine. */
242
243	l32i	a2, a7, CP_REGS_TAB_OFFSET
244	l32i	a3, a7, CP_REGS_TAB_LOAD
245	add	a2, a2, a9
246	callx0	a3
247
248	/* Restore all registers and return from exception handler. */
249
250	l32i	a10, a1, PT_AREG10
251	l32i	a9, a1, PT_AREG9
252	l32i	a8, a1, PT_AREG8
253	l32i	a7, a1, PT_AREG7
254	l32i	a6, a1, PT_AREG6
255	l32i	a5, a1, PT_AREG5
256	l32i	a4, a1, PT_AREG4
257
258	l32i	a0, a1, PT_SAR
259	l32i	a3, a1, PT_AREG3
260	l32i	a2, a1, PT_AREG2
261	wsr	a0, sar
262	l32i	a0, a1, PT_AREG0
263	l32i	a1, a1, PT_AREG1
264
265	rfe
266
267ENDPROC(fast_coprocessor)
268
269	.text
270
271/*
272 * coprocessor_flush(struct thread_info*, index)
273 *                             a2        a3
274 *
275 * Save coprocessor registers for coprocessor 'index'.
276 * The register values are saved to or loaded from the coprocessor area
277 * inside the task_info structure.
278 *
279 * Note that this function doesn't update the coprocessor_owner information!
280 *
281 */
282
283ENTRY(coprocessor_flush)
284
285	abi_entry_default
286
287	movi	a4, .Lcp_regs_jump_table
288	addx8	a4, a3, a4
289	addx4	a3, a3, a4
290	l32i	a4, a3, CP_REGS_TAB_SAVE
291	beqz	a4, 1f
292	l32i	a3, a3, CP_REGS_TAB_OFFSET
293	add	a2, a2, a3
294	mov	a7, a0
295	callx0	a4
296	mov	a0, a7
2971:
298	abi_ret_default
299
300ENDPROC(coprocessor_flush)
301
302#endif /* XTENSA_HAVE_COPROCESSORS */
303