1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * SMP support for BPA machines.
4 *
5 * Dave Engebretsen, Peter Bergner, and
6 * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
7 *
8 * Plus various changes from other IBM teams...
9 */
10
11 #undef DEBUG
12
13 #include <linux/kernel.h>
14 #include <linux/sched.h>
15 #include <linux/smp.h>
16 #include <linux/interrupt.h>
17 #include <linux/delay.h>
18 #include <linux/init.h>
19 #include <linux/spinlock.h>
20 #include <linux/cache.h>
21 #include <linux/err.h>
22 #include <linux/device.h>
23 #include <linux/cpu.h>
24 #include <linux/pgtable.h>
25
26 #include <asm/ptrace.h>
27 #include <linux/atomic.h>
28 #include <asm/irq.h>
29 #include <asm/page.h>
30 #include <asm/io.h>
31 #include <asm/prom.h>
32 #include <asm/smp.h>
33 #include <asm/paca.h>
34 #include <asm/machdep.h>
35 #include <asm/cputable.h>
36 #include <asm/firmware.h>
37 #include <asm/rtas.h>
38 #include <asm/cputhreads.h>
39 #include <asm/code-patching.h>
40
41 #include "interrupt.h"
42 #include <asm/udbg.h>
43
44 #ifdef DEBUG
45 #define DBG(fmt...) udbg_printf(fmt)
46 #else
47 #define DBG(fmt...)
48 #endif
49
50 /*
51 * The Primary thread of each non-boot processor was started from the OF client
52 * interface by prom_hold_cpus and is spinning on secondary_hold_spinloop.
53 */
54 static cpumask_t of_spin_map;
55
56 /**
57 * smp_startup_cpu() - start the given cpu
58 *
59 * At boot time, there is nothing to do for primary threads which were
60 * started from Open Firmware. For anything else, call RTAS with the
61 * appropriate start location.
62 *
63 * Returns:
64 * 0 - failure
65 * 1 - success
66 */
smp_startup_cpu(unsigned int lcpu)67 static inline int smp_startup_cpu(unsigned int lcpu)
68 {
69 int status;
70 unsigned long start_here =
71 __pa(ppc_function_entry(generic_secondary_smp_init));
72 unsigned int pcpu;
73 int start_cpu;
74
75 if (cpumask_test_cpu(lcpu, &of_spin_map))
76 /* Already started by OF and sitting in spin loop */
77 return 1;
78
79 pcpu = get_hard_smp_processor_id(lcpu);
80
81 /* Fixup atomic count: it exited inside IRQ handler. */
82 task_thread_info(paca_ptrs[lcpu]->__current)->preempt_count = 0;
83
84 /*
85 * If the RTAS start-cpu token does not exist then presume the
86 * cpu is already spinning.
87 */
88 start_cpu = rtas_token("start-cpu");
89 if (start_cpu == RTAS_UNKNOWN_SERVICE)
90 return 1;
91
92 status = rtas_call(start_cpu, 3, 1, NULL, pcpu, start_here, lcpu);
93 if (status != 0) {
94 printk(KERN_ERR "start-cpu failed: %i\n", status);
95 return 0;
96 }
97
98 return 1;
99 }
100
smp_cell_setup_cpu(int cpu)101 static void smp_cell_setup_cpu(int cpu)
102 {
103 if (cpu != boot_cpuid)
104 iic_setup_cpu();
105
106 /*
107 * change default DABRX to allow user watchpoints
108 */
109 mtspr(SPRN_DABRX, DABRX_KERNEL | DABRX_USER);
110 }
111
smp_cell_kick_cpu(int nr)112 static int smp_cell_kick_cpu(int nr)
113 {
114 if (nr < 0 || nr >= nr_cpu_ids)
115 return -EINVAL;
116
117 if (!smp_startup_cpu(nr))
118 return -ENOENT;
119
120 /*
121 * The processor is currently spinning, waiting for the
122 * cpu_start field to become non-zero After we set cpu_start,
123 * the processor will continue on to secondary_start
124 */
125 paca_ptrs[nr]->cpu_start = 1;
126
127 return 0;
128 }
129
130 static struct smp_ops_t bpa_iic_smp_ops = {
131 .message_pass = iic_message_pass,
132 .probe = iic_request_IPIs,
133 .kick_cpu = smp_cell_kick_cpu,
134 .setup_cpu = smp_cell_setup_cpu,
135 .cpu_bootable = smp_generic_cpu_bootable,
136 };
137
138 /* This is called very early */
smp_init_cell(void)139 void __init smp_init_cell(void)
140 {
141 int i;
142
143 DBG(" -> smp_init_cell()\n");
144
145 smp_ops = &bpa_iic_smp_ops;
146
147 /* Mark threads which are still spinning in hold loops. */
148 if (cpu_has_feature(CPU_FTR_SMT)) {
149 for_each_present_cpu(i) {
150 if (cpu_thread_in_core(i) == 0)
151 cpumask_set_cpu(i, &of_spin_map);
152 }
153 } else
154 cpumask_copy(&of_spin_map, cpu_present_mask);
155
156 cpumask_clear_cpu(boot_cpuid, &of_spin_map);
157
158 /* Non-lpar has additional take/give timebase */
159 if (rtas_token("freeze-time-base") != RTAS_UNKNOWN_SERVICE) {
160 smp_ops->give_timebase = rtas_give_timebase;
161 smp_ops->take_timebase = rtas_take_timebase;
162 }
163
164 DBG(" <- smp_init_cell()\n");
165 }
166
