1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * PowerNV OPAL in-memory console interface
4  *
5  * Copyright 2014 IBM Corp.
6  */
7 
8 #include <asm/io.h>
9 #include <asm/opal.h>
10 #include <linux/debugfs.h>
11 #include <linux/of.h>
12 #include <linux/types.h>
13 #include <asm/barrier.h>
14 
15 #include "powernv.h"
16 
17 /* OPAL in-memory console. Defined in OPAL source at core/console.c */
18 struct memcons {
19 	__be64 magic;
20 #define MEMCONS_MAGIC	0x6630696567726173L
21 	__be64 obuf_phys;
22 	__be64 ibuf_phys;
23 	__be32 obuf_size;
24 	__be32 ibuf_size;
25 	__be32 out_pos;
26 #define MEMCONS_OUT_POS_WRAP	0x80000000u
27 #define MEMCONS_OUT_POS_MASK	0x00ffffffu
28 	__be32 in_prod;
29 	__be32 in_cons;
30 };
31 
32 static struct memcons *opal_memcons = NULL;
33 
34 ssize_t memcons_copy(struct memcons *mc, char *to, loff_t pos, size_t count)
35 {
36 	const char *conbuf;
37 	ssize_t ret;
38 	size_t first_read = 0;
39 	uint32_t out_pos, avail;
40 
41 	if (!mc)
42 		return -ENODEV;
43 
44 	out_pos = be32_to_cpu(READ_ONCE(mc->out_pos));
45 
46 	/* Now we've read out_pos, put a barrier in before reading the new
47 	 * data it points to in conbuf. */
48 	smp_rmb();
49 
50 	conbuf = phys_to_virt(be64_to_cpu(mc->obuf_phys));
51 
52 	/* When the buffer has wrapped, read from the out_pos marker to the end
53 	 * of the buffer, and then read the remaining data as in the un-wrapped
54 	 * case. */
55 	if (out_pos & MEMCONS_OUT_POS_WRAP) {
56 
57 		out_pos &= MEMCONS_OUT_POS_MASK;
58 		avail = be32_to_cpu(mc->obuf_size) - out_pos;
59 
60 		ret = memory_read_from_buffer(to, count, &pos,
61 				conbuf + out_pos, avail);
62 
63 		if (ret < 0)
64 			goto out;
65 
66 		first_read = ret;
67 		to += first_read;
68 		count -= first_read;
69 		pos -= avail;
70 
71 		if (count <= 0)
72 			goto out;
73 	}
74 
75 	/* Sanity check. The firmware should not do this to us. */
76 	if (out_pos > be32_to_cpu(mc->obuf_size)) {
77 		pr_err("OPAL: memory console corruption. Aborting read.\n");
78 		return -EINVAL;
79 	}
80 
81 	ret = memory_read_from_buffer(to, count, &pos, conbuf, out_pos);
82 
83 	if (ret < 0)
84 		goto out;
85 
86 	ret += first_read;
87 out:
88 	return ret;
89 }
90 
91 ssize_t opal_msglog_copy(char *to, loff_t pos, size_t count)
92 {
93 	return memcons_copy(opal_memcons, to, pos, count);
94 }
95 
96 static ssize_t opal_msglog_read(struct file *file, struct kobject *kobj,
97 				struct bin_attribute *bin_attr, char *to,
98 				loff_t pos, size_t count)
99 {
100 	return opal_msglog_copy(to, pos, count);
101 }
102 
103 static struct bin_attribute opal_msglog_attr = {
104 	.attr = {.name = "msglog", .mode = 0400},
105 	.read = opal_msglog_read
106 };
107 
108 struct memcons *memcons_init(struct device_node *node, const char *mc_prop_name)
109 {
110 	u64 mcaddr;
111 	struct memcons *mc;
112 
113 	if (of_property_read_u64(node, mc_prop_name, &mcaddr)) {
114 		pr_warn("%s property not found, no message log\n",
115 			mc_prop_name);
116 		goto out_err;
117 	}
118 
119 	mc = phys_to_virt(mcaddr);
120 	if (!mc) {
121 		pr_warn("memory console address is invalid\n");
122 		goto out_err;
123 	}
124 
125 	if (be64_to_cpu(mc->magic) != MEMCONS_MAGIC) {
126 		pr_warn("memory console version is invalid\n");
127 		goto out_err;
128 	}
129 
130 	return mc;
131 
132 out_err:
133 	return NULL;
134 }
135 
136 u32 memcons_get_size(struct memcons *mc)
137 {
138 	return be32_to_cpu(mc->ibuf_size) + be32_to_cpu(mc->obuf_size);
139 }
140 
141 void __init opal_msglog_init(void)
142 {
143 	opal_memcons = memcons_init(opal_node, "ibm,opal-memcons");
144 	if (!opal_memcons) {
145 		pr_warn("OPAL: memcons failed to load from ibm,opal-memcons\n");
146 		return;
147 	}
148 
149 	opal_msglog_attr.size = memcons_get_size(opal_memcons);
150 }
151 
152 void __init opal_msglog_sysfs_init(void)
153 {
154 	if (!opal_memcons) {
155 		pr_warn("OPAL: message log initialisation failed, not creating sysfs entry\n");
156 		return;
157 	}
158 
159 	if (sysfs_create_bin_file(opal_kobj, &opal_msglog_attr) != 0)
160 		pr_warn("OPAL: sysfs file creation failed\n");
161 }
162