1 /*
2  * Spin Table SMP initialisation
3  *
4  * Copyright (C) 2013 ARM Ltd.
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License version 2 as
8  * published by the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License
16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
17  */
18 
19 #include <linux/delay.h>
20 #include <linux/init.h>
21 #include <linux/of.h>
22 #include <linux/smp.h>
23 #include <linux/types.h>
24 
25 #include <asm/cacheflush.h>
26 #include <asm/cpu_ops.h>
27 #include <asm/cputype.h>
28 #include <asm/io.h>
29 #include <asm/smp_plat.h>
30 
31 extern void secondary_holding_pen(void);
32 volatile unsigned long secondary_holding_pen_release = INVALID_HWID;
33 
34 static phys_addr_t cpu_release_addr[NR_CPUS];
35 
36 /*
37  * Write secondary_holding_pen_release in a way that is guaranteed to be
38  * visible to all observers, irrespective of whether they're taking part
39  * in coherency or not.  This is necessary for the hotplug code to work
40  * reliably.
41  */
42 static void write_pen_release(u64 val)
43 {
44 	void *start = (void *)&secondary_holding_pen_release;
45 	unsigned long size = sizeof(secondary_holding_pen_release);
46 
47 	secondary_holding_pen_release = val;
48 	__flush_dcache_area(start, size);
49 }
50 
51 
52 static int smp_spin_table_cpu_init(struct device_node *dn, unsigned int cpu)
53 {
54 	/*
55 	 * Determine the address from which the CPU is polling.
56 	 */
57 	if (of_property_read_u64(dn, "cpu-release-addr",
58 				 &cpu_release_addr[cpu])) {
59 		pr_err("CPU %d: missing or invalid cpu-release-addr property\n",
60 		       cpu);
61 
62 		return -1;
63 	}
64 
65 	return 0;
66 }
67 
68 static int smp_spin_table_cpu_prepare(unsigned int cpu)
69 {
70 	__le64 __iomem *release_addr;
71 
72 	if (!cpu_release_addr[cpu])
73 		return -ENODEV;
74 
75 	/*
76 	 * The cpu-release-addr may or may not be inside the linear mapping.
77 	 * As ioremap_cache will either give us a new mapping or reuse the
78 	 * existing linear mapping, we can use it to cover both cases. In
79 	 * either case the memory will be MT_NORMAL.
80 	 */
81 	release_addr = ioremap_cache(cpu_release_addr[cpu],
82 				     sizeof(*release_addr));
83 	if (!release_addr)
84 		return -ENOMEM;
85 
86 	/*
87 	 * We write the release address as LE regardless of the native
88 	 * endianess of the kernel. Therefore, any boot-loaders that
89 	 * read this address need to convert this address to the
90 	 * boot-loader's endianess before jumping. This is mandated by
91 	 * the boot protocol.
92 	 */
93 	writeq_relaxed(__pa(secondary_holding_pen), release_addr);
94 	__flush_dcache_area((__force void *)release_addr,
95 			    sizeof(*release_addr));
96 
97 	/*
98 	 * Send an event to wake up the secondary CPU.
99 	 */
100 	sev();
101 
102 	iounmap(release_addr);
103 
104 	return 0;
105 }
106 
107 static int smp_spin_table_cpu_boot(unsigned int cpu)
108 {
109 	/*
110 	 * Update the pen release flag.
111 	 */
112 	write_pen_release(cpu_logical_map(cpu));
113 
114 	/*
115 	 * Send an event, causing the secondaries to read pen_release.
116 	 */
117 	sev();
118 
119 	return 0;
120 }
121 
122 const struct cpu_operations smp_spin_table_ops = {
123 	.name		= "spin-table",
124 	.cpu_init	= smp_spin_table_cpu_init,
125 	.cpu_prepare	= smp_spin_table_cpu_prepare,
126 	.cpu_boot	= smp_spin_table_cpu_boot,
127 };
128