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 
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 = 0444},
96 	.read = opal_msglog_read
97 };
98 
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