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 	size_t ret, first_read = 0;
41 	uint32_t out_pos, avail;
42 
43 	if (!mc)
44 		return -ENODEV;
45 
46 	out_pos = be32_to_cpu(ACCESS_ONCE(mc->out_pos));
47 
48 	/* Now we've read out_pos, put a barrier in before reading the new
49 	 * data it points to in conbuf. */
50 	smp_rmb();
51 
52 	conbuf = phys_to_virt(be64_to_cpu(mc->obuf_phys));
53 
54 	/* When the buffer has wrapped, read from the out_pos marker to the end
55 	 * of the buffer, and then read the remaining data as in the un-wrapped
56 	 * case. */
57 	if (out_pos & MEMCONS_OUT_POS_WRAP) {
58 
59 		out_pos &= MEMCONS_OUT_POS_MASK;
60 		avail = be32_to_cpu(mc->obuf_size) - out_pos;
61 
62 		ret = memory_read_from_buffer(to, count, &pos,
63 				conbuf + out_pos, avail);
64 
65 		if (ret < 0)
66 			goto out;
67 
68 		first_read = ret;
69 		to += first_read;
70 		count -= first_read;
71 		pos -= avail;
72 	}
73 
74 	/* Sanity check. The firmware should not do this to us. */
75 	if (out_pos > be32_to_cpu(mc->obuf_size)) {
76 		pr_err("OPAL: memory console corruption. Aborting read.\n");
77 		return -EINVAL;
78 	}
79 
80 	ret = memory_read_from_buffer(to, count, &pos, conbuf, out_pos);
81 
82 	if (ret < 0)
83 		goto out;
84 
85 	ret += first_read;
86 out:
87 	return ret;
88 }
89 
90 static struct bin_attribute opal_msglog_attr = {
91 	.attr = {.name = "msglog", .mode = 0444},
92 	.read = opal_msglog_read
93 };
94 
95 void __init opal_msglog_init(void)
96 {
97 	u64 mcaddr;
98 	struct memcons *mc;
99 
100 	if (of_property_read_u64(opal_node, "ibm,opal-memcons", &mcaddr)) {
101 		pr_warn("OPAL: Property ibm,opal-memcons not found, no message log\n");
102 		return;
103 	}
104 
105 	mc = phys_to_virt(mcaddr);
106 	if (!mc) {
107 		pr_warn("OPAL: memory console address is invalid\n");
108 		return;
109 	}
110 
111 	if (be64_to_cpu(mc->magic) != MEMCONS_MAGIC) {
112 		pr_warn("OPAL: memory console version is invalid\n");
113 		return;
114 	}
115 
116 	opal_msglog_attr.private = mc;
117 
118 	if (sysfs_create_bin_file(opal_kobj, &opal_msglog_attr) != 0)
119 		pr_warn("OPAL: sysfs file creation failed\n");
120 }
121