xref: /openbmc/linux/arch/arm/mach-spear/platsmp.c (revision c164620a)
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  */
spear_write_pen_release(int val)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 
spear13xx_secondary_init(unsigned int cpu)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 
spear13xx_boot_secondary(unsigned int cpu,struct task_struct * idle)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  */
spear13xx_smp_init_cpus(void)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 
spear13xx_smp_prepare_cpus(unsigned int max_cpus)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