1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/*
3 * Copyright 2018, IBM Corporation.
4 *
5 * This file contains general idle entry/exit functions to save
6 * and restore stack and NVGPRs which allows C code to call idle
7 * states that lose GPRs, and it will return transparently with
8 * SRR1 wakeup reason return value.
9 *
10 * The platform / CPU caller must ensure SPRs and any other non-GPR
11 * state is saved and restored correctly, handle KVM, interrupts, etc.
12 */
13
14#include <asm/ppc_asm.h>
15#include <asm/asm-offsets.h>
16#include <asm/ppc-opcode.h>
17#include <asm/cpuidle.h>
18#include <asm/thread_info.h> /* TLF_NAPPING */
19
20#ifdef CONFIG_PPC_P7_NAP
21/*
22 * Desired PSSCR in r3
23 *
24 * No state will be lost regardless of wakeup mechanism (interrupt or NIA).
25 *
26 * An EC=0 type wakeup will return with a value of 0. SRESET wakeup (which can
27 * happen with xscom SRESET and possibly MCE) may clobber volatiles except LR,
28 * and must blr, to return to caller with r3 set according to caller's expected
29 * return code (for Book3S/64 that is SRR1).
30 */
31_GLOBAL(isa300_idle_stop_noloss)
32 mtspr SPRN_PSSCR,r3
33 PPC_STOP
34 li r3,0
35 blr
36
37/*
38 * Desired PSSCR in r3
39 *
40 * GPRs may be lost, so they are saved here. Wakeup is by interrupt only.
41 * The SRESET wakeup returns to this function's caller by calling
42 * idle_return_gpr_loss with r3 set to desired return value.
43 *
44 * A wakeup without GPR loss may alteratively be handled as in
45 * isa300_idle_stop_noloss and blr directly, as an optimisation.
46 *
47 * The caller is responsible for saving/restoring SPRs, MSR, timebase,
48 * etc.
49 */
50_GLOBAL(isa300_idle_stop_mayloss)
51 mtspr SPRN_PSSCR,r3
52 std r1,PACAR1(r13)
53 mflr r4
54 mfcr r5
55 /*
56 * Use the stack red zone rather than a new frame for saving regs since
57 * in the case of no GPR loss the wakeup code branches directly back to
58 * the caller without deallocating the stack frame first.
59 */
60 std r2,-8*1(r1)
61 std r14,-8*2(r1)
62 std r15,-8*3(r1)
63 std r16,-8*4(r1)
64 std r17,-8*5(r1)
65 std r18,-8*6(r1)
66 std r19,-8*7(r1)
67 std r20,-8*8(r1)
68 std r21,-8*9(r1)
69 std r22,-8*10(r1)
70 std r23,-8*11(r1)
71 std r24,-8*12(r1)
72 std r25,-8*13(r1)
73 std r26,-8*14(r1)
74 std r27,-8*15(r1)
75 std r28,-8*16(r1)
76 std r29,-8*17(r1)
77 std r30,-8*18(r1)
78 std r31,-8*19(r1)
79 std r4,-8*20(r1)
80 std r5,-8*21(r1)
81 /* 168 bytes */
82 PPC_STOP
83 b . /* catch bugs */
84
85/*
86 * Desired return value in r3
87 *
88 * The idle wakeup SRESET interrupt can call this after calling
89 * to return to the idle sleep function caller with r3 as the return code.
90 *
91 * This must not be used if idle was entered via a _noloss function (use
92 * a simple blr instead).
93 */
94_GLOBAL(idle_return_gpr_loss)
95 ld r1,PACAR1(r13)
96 ld r4,-8*20(r1)
97 ld r5,-8*21(r1)
98 mtlr r4
99 mtcr r5
100 /*
101 * KVM nap requires r2 to be saved, rather than just restoring it
102 * from PACATOC. This could be avoided for that less common case
103 * if KVM saved its r2.
104 */
105 ld r2,-8*1(r1)
106 ld r14,-8*2(r1)
107 ld r15,-8*3(r1)
108 ld r16,-8*4(r1)
109 ld r17,-8*5(r1)
110 ld r18,-8*6(r1)
111 ld r19,-8*7(r1)
112 ld r20,-8*8(r1)
113 ld r21,-8*9(r1)
114 ld r22,-8*10(r1)
115 ld r23,-8*11(r1)
116 ld r24,-8*12(r1)
117 ld r25,-8*13(r1)
118 ld r26,-8*14(r1)
119 ld r27,-8*15(r1)
120 ld r28,-8*16(r1)
121 ld r29,-8*17(r1)
122 ld r30,-8*18(r1)
123 ld r31,-8*19(r1)
124 blr
125
126/*
127 * This is the sequence required to execute idle instructions, as
128 * specified in ISA v2.07 (and earlier). MSR[IR] and MSR[DR] must be 0.
129 * We have to store a GPR somewhere, ptesync, then reload it, and create
130 * a false dependency on the result of the load. It doesn't matter which
131 * GPR we store, or where we store it. We have already stored r2 to the
132 * stack at -8(r1) in isa206_idle_insn_mayloss, so use that.
133 */
134#define IDLE_STATE_ENTER_SEQ_NORET(IDLE_INST) \
135 /* Magic NAP/SLEEP/WINKLE mode enter sequence */ \
136 std r2,-8(r1); \
137 ptesync; \
138 ld r2,-8(r1); \
139236: cmpd cr0,r2,r2; \
140 bne 236b; \
141 IDLE_INST; \
142 b . /* catch bugs */
143
144/*
145 * Desired instruction type in r3
146 *
147 * GPRs may be lost, so they are saved here. Wakeup is by interrupt only.
148 * The SRESET wakeup returns to this function's caller by calling
149 * idle_return_gpr_loss with r3 set to desired return value.
150 *
151 * A wakeup without GPR loss may alteratively be handled as in
152 * isa300_idle_stop_noloss and blr directly, as an optimisation.
153 *
154 * The caller is responsible for saving/restoring SPRs, MSR, timebase,
155 * etc.
156 *
157 * This must be called in real-mode (MSR_IDLE).
158 */
159_GLOBAL(isa206_idle_insn_mayloss)
160 std r1,PACAR1(r13)
161 mflr r4
162 mfcr r5
163 /*
164 * Use the stack red zone rather than a new frame for saving regs since
165 * in the case of no GPR loss the wakeup code branches directly back to
166 * the caller without deallocating the stack frame first.
167 */
168 std r2,-8*1(r1)
169 std r14,-8*2(r1)
170 std r15,-8*3(r1)
171 std r16,-8*4(r1)
172 std r17,-8*5(r1)
173 std r18,-8*6(r1)
174 std r19,-8*7(r1)
175 std r20,-8*8(r1)
176 std r21,-8*9(r1)
177 std r22,-8*10(r1)
178 std r23,-8*11(r1)
179 std r24,-8*12(r1)
180 std r25,-8*13(r1)
181 std r26,-8*14(r1)
182 std r27,-8*15(r1)
183 std r28,-8*16(r1)
184 std r29,-8*17(r1)
185 std r30,-8*18(r1)
186 std r31,-8*19(r1)
187 std r4,-8*20(r1)
188 std r5,-8*21(r1)
189 cmpwi r3,PNV_THREAD_NAP
190 bne 1f
191 IDLE_STATE_ENTER_SEQ_NORET(PPC_NAP)
1921: cmpwi r3,PNV_THREAD_SLEEP
193 bne 2f
194 IDLE_STATE_ENTER_SEQ_NORET(PPC_SLEEP)
1952: IDLE_STATE_ENTER_SEQ_NORET(PPC_WINKLE)
196#endif
197
198#ifdef CONFIG_PPC_970_NAP
199_GLOBAL(power4_idle_nap)
200 LOAD_REG_IMMEDIATE(r7, MSR_KERNEL|MSR_EE|MSR_POW)
201 ld r9,PACA_THREAD_INFO(r13)
202 ld r8,TI_LOCAL_FLAGS(r9)
203 ori r8,r8,_TLF_NAPPING
204 std r8,TI_LOCAL_FLAGS(r9)
205 /*
206 * NAPPING bit is set, from this point onward power4_fixup_nap
207 * will cause exceptions to return to power4_idle_nap_return.
208 */
2091: sync
210 isync
211 mtmsrd r7
212 isync
213 b 1b
214
215 .globl power4_idle_nap_return
216power4_idle_nap_return:
217 blr
218#endif
219

source code of linux/arch/powerpc/kernel/idle_book3s.S