1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * arch/arm/mach-spear13xx/platsmp.c
4 *
5 * based upon linux/arch/arm/mach-realview/platsmp.c
6 *
7 * Copyright (C) 2012 ST Microelectronics Ltd.
8 * Shiraz Hashim <shiraz.linux.kernel@gmail.com>
9 */
10
11 #include <linux/delay.h>
12 #include <linux/jiffies.h>
13 #include <linux/io.h>
14 #include <linux/smp.h>
15 #include <asm/cacheflush.h>
16 #include <asm/smp_scu.h>
17 #include "spear.h"
18 #include "generic.h"
19
20 /* XXX spear_pen_release is cargo culted code - DO NOT COPY XXX */
21 volatile int spear_pen_release = -1;
22
23 /*
24 * XXX CARGO CULTED CODE - DO NOT COPY XXX
25 *
26 * Write spear_pen_release in a way that is guaranteed to be visible to
27 * all observers, irrespective of whether they're taking part in coherency
28 * or not. This is necessary for the hotplug code to work reliably.
29 */
30 static void spear_write_pen_release(int val)
31 {
32 spear_pen_release = val;
33 smp_wmb();
34 sync_cache_w(&spear_pen_release);
35 }
36
37 static DEFINE_SPINLOCK(boot_lock);
38
39 static void __iomem *scu_base = IOMEM(VA_SCU_BASE);
40
41 static void spear13xx_secondary_init(unsigned int cpu)
42 {
43 /*
44 * let the primary processor know we're out of the
45 * pen, then head off into the C entry point
46 */
47 spear_write_pen_release(-1);
48
49 /*
50 * Synchronise with the boot thread.
51 */
52 spin_lock(&boot_lock);
53 spin_unlock(&boot_lock);
54 }
55
56 static int spear13xx_boot_secondary(unsigned int cpu, struct task_struct *idle)
57 {
58 unsigned long timeout;
59
60 /*
61 * set synchronisation state between this boot processor
62 * and the secondary one
63 */
64 spin_lock(&boot_lock);
65
66 /*
67 * The secondary processor is waiting to be released from
68 * the holding pen - release it, then wait for it to flag
69 * that it has been released by resetting spear_pen_release.
70 *
71 * Note that "spear_pen_release" is the hardware CPU ID, whereas
72 * "cpu" is Linux's internal ID.
73 */
74 spear_write_pen_release(cpu);
75
76 timeout = jiffies + (1 * HZ);
77 while (time_before(jiffies, timeout)) {
78 smp_rmb();
79 if (spear_pen_release == -1)
80 break;
81
82 udelay(10);
83 }
84
85 /*
86 * now the secondary core is starting up let it run its
87 * calibrations, then wait for it to finish
88 */
89 spin_unlock(&boot_lock);
90
91 return spear_pen_release != -1 ? -ENOSYS : 0;
92 }
93
94 /*
95 * Initialise the CPU possible map early - this describes the CPUs
96 * which may be present or become present in the system.
97 */
98 static void __init spear13xx_smp_init_cpus(void)
99 {
100 unsigned int i, ncores = scu_get_core_count(scu_base);
101
102 if (ncores > nr_cpu_ids) {
103 pr_warn("SMP: %u cores greater than maximum (%u), clipping\n",
104 ncores, nr_cpu_ids);
105 ncores = nr_cpu_ids;
106 }
107
108 for (i = 0; i < ncores; i++)
109 set_cpu_possible(i, true);
110 }
111
112 static void __init spear13xx_smp_prepare_cpus(unsigned int max_cpus)
113 {
114
115 scu_enable(scu_base);
116
117 /*
118 * Write the address of secondary startup into the system-wide location
119 * (presently it is in SRAM). The BootMonitor waits until it receives a
120 * soft interrupt, and then the secondary CPU branches to this address.
121 */
122 __raw_writel(__pa_symbol(spear13xx_secondary_startup), SYS_LOCATION);
123 }
124
125 const struct smp_operations spear13xx_smp_ops __initconst = {
126 .smp_init_cpus = spear13xx_smp_init_cpus,
127 .smp_prepare_cpus = spear13xx_smp_prepare_cpus,
128 .smp_secondary_init = spear13xx_secondary_init,
129 .smp_boot_secondary = spear13xx_boot_secondary,
130 #ifdef CONFIG_HOTPLUG_CPU
131 .cpu_die = spear13xx_cpu_die,
132 #endif
133 };
134
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