1 /*
2 * PowerNV OPAL in-memory console interface
3 *
4 * Copyright 2014 IBM Corp.
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12 #include <asm/io.h>
13 #include <asm/opal.h>
14 #include <linux/debugfs.h>
15 #include <linux/of.h>
16 #include <linux/types.h>
17 #include <asm/barrier.h>
18
19 /* OPAL in-memory console. Defined in OPAL source at core/console.c */
20 struct memcons {
21 __be64 magic;
22 #define MEMCONS_MAGIC 0x6630696567726173L
23 __be64 obuf_phys;
24 __be64 ibuf_phys;
25 __be32 obuf_size;
26 __be32 ibuf_size;
27 __be32 out_pos;
28 #define MEMCONS_OUT_POS_WRAP 0x80000000u
29 #define MEMCONS_OUT_POS_MASK 0x00ffffffu
30 __be32 in_prod;
31 __be32 in_cons;
32 };
33
opal_msglog_read(struct file * file,struct kobject * kobj,struct bin_attribute * bin_attr,char * to,loff_t pos,size_t count)34 static ssize_t opal_msglog_read(struct file *file, struct kobject *kobj,
35 struct bin_attribute *bin_attr, char *to,
36 loff_t pos, size_t count)
37 {
38 struct memcons *mc = bin_attr->private;
39 const char *conbuf;
40 ssize_t ret;
41 size_t first_read = 0;
42 uint32_t out_pos, avail;
43
44 if (!mc)
45 return -ENODEV;
46
47 out_pos = be32_to_cpu(ACCESS_ONCE(mc->out_pos));
48
49 /* Now we've read out_pos, put a barrier in before reading the new
50 * data it points to in conbuf. */
51 smp_rmb();
52
53 conbuf = phys_to_virt(be64_to_cpu(mc->obuf_phys));
54
55 /* When the buffer has wrapped, read from the out_pos marker to the end
56 * of the buffer, and then read the remaining data as in the un-wrapped
57 * case. */
58 if (out_pos & MEMCONS_OUT_POS_WRAP) {
59
60 out_pos &= MEMCONS_OUT_POS_MASK;
61 avail = be32_to_cpu(mc->obuf_size) - out_pos;
62
63 ret = memory_read_from_buffer(to, count, &pos,
64 conbuf + out_pos, avail);
65
66 if (ret < 0)
67 goto out;
68
69 first_read = ret;
70 to += first_read;
71 count -= first_read;
72 pos -= avail;
73
74 if (count <= 0)
75 goto out;
76 }
77
78 /* Sanity check. The firmware should not do this to us. */
79 if (out_pos > be32_to_cpu(mc->obuf_size)) {
80 pr_err("OPAL: memory console corruption. Aborting read.\n");
81 return -EINVAL;
82 }
83
84 ret = memory_read_from_buffer(to, count, &pos, conbuf, out_pos);
85
86 if (ret < 0)
87 goto out;
88
89 ret += first_read;
90 out:
91 return ret;
92 }
93
94 static struct bin_attribute opal_msglog_attr = {
95 .attr = {.name = "msglog", .mode = 0400},
96 .read = opal_msglog_read
97 };
98
opal_msglog_init(void)99 void __init opal_msglog_init(void)
100 {
101 u64 mcaddr;
102 struct memcons *mc;
103
104 if (of_property_read_u64(opal_node, "ibm,opal-memcons", &mcaddr)) {
105 pr_warn("OPAL: Property ibm,opal-memcons not found, no message log\n");
106 return;
107 }
108
109 mc = phys_to_virt(mcaddr);
110 if (!mc) {
111 pr_warn("OPAL: memory console address is invalid\n");
112 return;
113 }
114
115 if (be64_to_cpu(mc->magic) != MEMCONS_MAGIC) {
116 pr_warn("OPAL: memory console version is invalid\n");
117 return;
118 }
119
120 opal_msglog_attr.private = mc;
121
122 if (sysfs_create_bin_file(opal_kobj, &opal_msglog_attr) != 0)
123 pr_warn("OPAL: sysfs file creation failed\n");
124 }
125