xref: /openbmc/linux/arch/arm/vfp/vfphw.S (revision c4a11bf4) 
1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 *  linux/arch/arm/vfp/vfphw.S
4 *
5 *  Copyright (C) 2004 ARM Limited.
6 *  Written by Deep Blue Solutions Limited.
7 *
8 * This code is called from the kernel's undefined instruction trap.
9 * r9 holds the return address for successful handling.
10 * lr holds the return address for unrecognised instructions.
11 * r10 points at the start of the private FP workspace in the thread structure
12 * sp points to a struct pt_regs (as defined in include/asm/proc/ptrace.h)
13 */
14#include <linux/init.h>
15#include <linux/linkage.h>
16#include <asm/thread_info.h>
17#include <asm/vfpmacros.h>
18#include <linux/kern_levels.h>
19#include <asm/assembler.h>
20#include <asm/asm-offsets.h>
21
22	.macro	DBGSTR, str
23#ifdef DEBUG
24	stmfd	sp!, {r0-r3, ip, lr}
25	ldr	r0, =1f
26	bl	_printk
27	ldmfd	sp!, {r0-r3, ip, lr}
28
29	.pushsection .rodata, "a"
301:	.ascii	KERN_DEBUG "VFP: \str\n"
31	.byte	0
32	.previous
33#endif
34	.endm
35
36	.macro  DBGSTR1, str, arg
37#ifdef DEBUG
38	stmfd	sp!, {r0-r3, ip, lr}
39	mov	r1, \arg
40	ldr	r0, =1f
41	bl	_printk
42	ldmfd	sp!, {r0-r3, ip, lr}
43
44	.pushsection .rodata, "a"
451:	.ascii	KERN_DEBUG "VFP: \str\n"
46	.byte	0
47	.previous
48#endif
49	.endm
50
51	.macro  DBGSTR3, str, arg1, arg2, arg3
52#ifdef DEBUG
53	stmfd	sp!, {r0-r3, ip, lr}
54	mov	r3, \arg3
55	mov	r2, \arg2
56	mov	r1, \arg1
57	ldr	r0, =1f
58	bl	_printk
59	ldmfd	sp!, {r0-r3, ip, lr}
60
61	.pushsection .rodata, "a"
621:	.ascii	KERN_DEBUG "VFP: \str\n"
63	.byte	0
64	.previous
65#endif
66	.endm
67
68
69@ VFP hardware support entry point.
70@
71@  r0  = instruction opcode (32-bit ARM or two 16-bit Thumb)
72@  r2  = PC value to resume execution after successful emulation
73@  r9  = normal "successful" return address
74@  r10 = vfp_state union
75@  r11 = CPU number
76@  lr  = unrecognised instruction return address
77@  IRQs enabled.
78ENTRY(vfp_support_entry)
79	DBGSTR3	"instr %08x pc %08x state %p", r0, r2, r10
80
81	.fpu	vfpv2
82	VFPFMRX	r1, FPEXC		@ Is the VFP enabled?
83	DBGSTR1	"fpexc %08x", r1
84	tst	r1, #FPEXC_EN
85	bne	look_for_VFP_exceptions	@ VFP is already enabled
86
87	DBGSTR1 "enable %x", r10
88	ldr	r3, vfp_current_hw_state_address
89	orr	r1, r1, #FPEXC_EN	@ user FPEXC has the enable bit set
90	ldr	r4, [r3, r11, lsl #2]	@ vfp_current_hw_state pointer
91	bic	r5, r1, #FPEXC_EX	@ make sure exceptions are disabled
92	cmp	r4, r10			@ this thread owns the hw context?
93#ifndef CONFIG_SMP
94	@ For UP, checking that this thread owns the hw context is
95	@ sufficient to determine that the hardware state is valid.
96	beq	vfp_hw_state_valid
97
98	@ On UP, we lazily save the VFP context.  As a different
99	@ thread wants ownership of the VFP hardware, save the old
100	@ state if there was a previous (valid) owner.
101
102	VFPFMXR	FPEXC, r5		@ enable VFP, disable any pending
103					@ exceptions, so we can get at the
104					@ rest of it
105
106	DBGSTR1	"save old state %p", r4
107	cmp	r4, #0			@ if the vfp_current_hw_state is NULL
108	beq	vfp_reload_hw		@ then the hw state needs reloading
109	VFPFSTMIA r4, r5		@ save the working registers
110	VFPFMRX	r5, FPSCR		@ current status
111#ifndef CONFIG_CPU_FEROCEON
112	tst	r1, #FPEXC_EX		@ is there additional state to save?
113	beq	1f
114	VFPFMRX	r6, FPINST		@ FPINST (only if FPEXC.EX is set)
115	tst	r1, #FPEXC_FP2V		@ is there an FPINST2 to read?
116	beq	1f
117	VFPFMRX	r8, FPINST2		@ FPINST2 if needed (and present)
1181:
119#endif
120	stmia	r4, {r1, r5, r6, r8}	@ save FPEXC, FPSCR, FPINST, FPINST2
121vfp_reload_hw:
122
123#else
124	@ For SMP, if this thread does not own the hw context, then we
125	@ need to reload it.  No need to save the old state as on SMP,
126	@ we always save the state when we switch away from a thread.
127	bne	vfp_reload_hw
128
129	@ This thread has ownership of the current hardware context.
130	@ However, it may have been migrated to another CPU, in which
131	@ case the saved state is newer than the hardware context.
132	@ Check this by looking at the CPU number which the state was
133	@ last loaded onto.
134	ldr	ip, [r10, #VFP_CPU]
135	teq	ip, r11
136	beq	vfp_hw_state_valid
137
138vfp_reload_hw:
139	@ We're loading this threads state into the VFP hardware. Update
140	@ the CPU number which contains the most up to date VFP context.
141	str	r11, [r10, #VFP_CPU]
142
143	VFPFMXR	FPEXC, r5		@ enable VFP, disable any pending
144					@ exceptions, so we can get at the
145					@ rest of it
146#endif
147
148	DBGSTR1	"load state %p", r10
149	str	r10, [r3, r11, lsl #2]	@ update the vfp_current_hw_state pointer
150					@ Load the saved state back into the VFP
151	VFPFLDMIA r10, r5		@ reload the working registers while
152					@ FPEXC is in a safe state
153	ldmia	r10, {r1, r5, r6, r8}	@ load FPEXC, FPSCR, FPINST, FPINST2
154#ifndef CONFIG_CPU_FEROCEON
155	tst	r1, #FPEXC_EX		@ is there additional state to restore?
156	beq	1f
157	VFPFMXR	FPINST, r6		@ restore FPINST (only if FPEXC.EX is set)
158	tst	r1, #FPEXC_FP2V		@ is there an FPINST2 to write?
159	beq	1f
160	VFPFMXR	FPINST2, r8		@ FPINST2 if needed (and present)
1611:
162#endif
163	VFPFMXR	FPSCR, r5		@ restore status
164
165@ The context stored in the VFP hardware is up to date with this thread
166vfp_hw_state_valid:
167	tst	r1, #FPEXC_EX
168	bne	process_exception	@ might as well handle the pending
169					@ exception before retrying branch
170					@ out before setting an FPEXC that
171					@ stops us reading stuff
172	VFPFMXR	FPEXC, r1		@ Restore FPEXC last
173	sub	r2, r2, #4		@ Retry current instruction - if Thumb
174	str	r2, [sp, #S_PC]		@ mode it's two 16-bit instructions,
175					@ else it's one 32-bit instruction, so
176					@ always subtract 4 from the following
177					@ instruction address.
178	dec_preempt_count_ti r10, r4
179	ret	r9			@ we think we have handled things
180
181
182look_for_VFP_exceptions:
183	@ Check for synchronous or asynchronous exception
184	tst	r1, #FPEXC_EX | FPEXC_DEX
185	bne	process_exception
186	@ On some implementations of the VFP subarch 1, setting FPSCR.IXE
187	@ causes all the CDP instructions to be bounced synchronously without
188	@ setting the FPEXC.EX bit
189	VFPFMRX	r5, FPSCR
190	tst	r5, #FPSCR_IXE
191	bne	process_exception
192
193	tst	r5, #FPSCR_LENGTH_MASK
194	beq	skip
195	orr	r1, r1, #FPEXC_DEX
196	b	process_exception
197skip:
198
199	@ Fall into hand on to next handler - appropriate coproc instr
200	@ not recognised by VFP
201
202	DBGSTR	"not VFP"
203	dec_preempt_count_ti r10, r4
204	ret	lr
205
206process_exception:
207	DBGSTR	"bounce"
208	mov	r2, sp			@ nothing stacked - regdump is at TOS
209	mov	lr, r9			@ setup for a return to the user code.
210
211	@ Now call the C code to package up the bounce to the support code
212	@   r0 holds the trigger instruction
213	@   r1 holds the FPEXC value
214	@   r2 pointer to register dump
215	b	VFP_bounce		@ we have handled this - the support
216					@ code will raise an exception if
217					@ required. If not, the user code will
218					@ retry the faulted instruction
219ENDPROC(vfp_support_entry)
220
221ENTRY(vfp_save_state)
222	@ Save the current VFP state
223	@ r0 - save location
224	@ r1 - FPEXC
225	DBGSTR1	"save VFP state %p", r0
226	VFPFSTMIA r0, r2		@ save the working registers
227	VFPFMRX	r2, FPSCR		@ current status
228	tst	r1, #FPEXC_EX		@ is there additional state to save?
229	beq	1f
230	VFPFMRX	r3, FPINST		@ FPINST (only if FPEXC.EX is set)
231	tst	r1, #FPEXC_FP2V		@ is there an FPINST2 to read?
232	beq	1f
233	VFPFMRX	r12, FPINST2		@ FPINST2 if needed (and present)
2341:
235	stmia	r0, {r1, r2, r3, r12}	@ save FPEXC, FPSCR, FPINST, FPINST2
236	ret	lr
237ENDPROC(vfp_save_state)
238
239	.align
240vfp_current_hw_state_address:
241	.word	vfp_current_hw_state
242
243	.macro	tbl_branch, base, tmp, shift
244#ifdef CONFIG_THUMB2_KERNEL
245	adr	\tmp, 1f
246	add	\tmp, \tmp, \base, lsl \shift
247	ret	\tmp
248#else
249	add	pc, pc, \base, lsl \shift
250	mov	r0, r0
251#endif
2521:
253	.endm
254
255ENTRY(vfp_get_float)
256	tbl_branch r0, r3, #3
257	.fpu	vfpv2
258	.irp	dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
2591:	vmov	r0, s\dr
260	ret	lr
261	.org	1b + 8
262	.endr
263	.irp	dr,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
2641:	vmov	r0, s\dr
265	ret	lr
266	.org	1b + 8
267	.endr
268ENDPROC(vfp_get_float)
269
270ENTRY(vfp_put_float)
271	tbl_branch r1, r3, #3
272	.fpu	vfpv2
273	.irp	dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
2741:	vmov	s\dr, r0
275	ret	lr
276	.org	1b + 8
277	.endr
278	.irp	dr,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
2791:	vmov	s\dr, r0
280	ret	lr
281	.org	1b + 8
282	.endr
283ENDPROC(vfp_put_float)
284
285ENTRY(vfp_get_double)
286	tbl_branch r0, r3, #3
287	.fpu	vfpv2
288	.irp	dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
2891:	vmov	r0, r1, d\dr
290	ret	lr
291	.org	1b + 8
292	.endr
293#ifdef CONFIG_VFPv3
294	@ d16 - d31 registers
295	.fpu	vfpv3
296	.irp	dr,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
2971:	vmov	r0, r1, d\dr
298	ret	lr
299	.org	1b + 8
300	.endr
301#endif
302
303	@ virtual register 16 (or 32 if VFPv3) for compare with zero
304	mov	r0, #0
305	mov	r1, #0
306	ret	lr
307ENDPROC(vfp_get_double)
308
309ENTRY(vfp_put_double)
310	tbl_branch r2, r3, #3
311	.fpu	vfpv2
312	.irp	dr,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
3131:	vmov	d\dr, r0, r1
314	ret	lr
315	.org	1b + 8
316	.endr
317#ifdef CONFIG_VFPv3
318	.fpu	vfpv3
319	@ d16 - d31 registers
320	.irp	dr,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31
3211:	vmov	d\dr, r0, r1
322	ret	lr
323	.org	1b + 8
324	.endr
325#endif
326ENDPROC(vfp_put_double)
327