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 /* OPAL in-memory console. Defined in OPAL source at core/console.c */
16 struct memcons {
17 	__be64 magic;
18 #define MEMCONS_MAGIC	0x6630696567726173L
19 	__be64 obuf_phys;
20 	__be64 ibuf_phys;
21 	__be32 obuf_size;
22 	__be32 ibuf_size;
23 	__be32 out_pos;
24 #define MEMCONS_OUT_POS_WRAP	0x80000000u
25 #define MEMCONS_OUT_POS_MASK	0x00ffffffu
26 	__be32 in_prod;
27 	__be32 in_cons;
28 };
29 
30 static struct memcons *opal_memcons = NULL;
31 
32 ssize_t opal_msglog_copy(char *to, loff_t pos, size_t count)
33 {
34 	const char *conbuf;
35 	ssize_t ret;
36 	size_t first_read = 0;
37 	uint32_t out_pos, avail;
38 
39 	if (!opal_memcons)
40 		return -ENODEV;
41 
42 	out_pos = be32_to_cpu(READ_ONCE(opal_memcons->out_pos));
43 
44 	/* Now we've read out_pos, put a barrier in before reading the new
45 	 * data it points to in conbuf. */
46 	smp_rmb();
47 
48 	conbuf = phys_to_virt(be64_to_cpu(opal_memcons->obuf_phys));
49 
50 	/* When the buffer has wrapped, read from the out_pos marker to the end
51 	 * of the buffer, and then read the remaining data as in the un-wrapped
52 	 * case. */
53 	if (out_pos & MEMCONS_OUT_POS_WRAP) {
54 
55 		out_pos &= MEMCONS_OUT_POS_MASK;
56 		avail = be32_to_cpu(opal_memcons->obuf_size) - out_pos;
57 
58 		ret = memory_read_from_buffer(to, count, &pos,
59 				conbuf + out_pos, avail);
60 
61 		if (ret < 0)
62 			goto out;
63 
64 		first_read = ret;
65 		to += first_read;
66 		count -= first_read;
67 		pos -= avail;
68 
69 		if (count <= 0)
70 			goto out;
71 	}
72 
73 	/* Sanity check. The firmware should not do this to us. */
74 	if (out_pos > be32_to_cpu(opal_memcons->obuf_size)) {
75 		pr_err("OPAL: memory console corruption. Aborting read.\n");
76 		return -EINVAL;
77 	}
78 
79 	ret = memory_read_from_buffer(to, count, &pos, conbuf, out_pos);
80 
81 	if (ret < 0)
82 		goto out;
83 
84 	ret += first_read;
85 out:
86 	return ret;
87 }
88 
89 static ssize_t opal_msglog_read(struct file *file, struct kobject *kobj,
90 				struct bin_attribute *bin_attr, char *to,
91 				loff_t pos, size_t count)
92 {
93 	return opal_msglog_copy(to, pos, count);
94 }
95 
96 static struct bin_attribute opal_msglog_attr = {
97 	.attr = {.name = "msglog", .mode = 0400},
98 	.read = opal_msglog_read
99 };
100 
101 void __init opal_msglog_init(void)
102 {
103 	u64 mcaddr;
104 	struct memcons *mc;
105 
106 	if (of_property_read_u64(opal_node, "ibm,opal-memcons", &mcaddr)) {
107 		pr_warn("OPAL: Property ibm,opal-memcons not found, no message log\n");
108 		return;
109 	}
110 
111 	mc = phys_to_virt(mcaddr);
112 	if (!mc) {
113 		pr_warn("OPAL: memory console address is invalid\n");
114 		return;
115 	}
116 
117 	if (be64_to_cpu(mc->magic) != MEMCONS_MAGIC) {
118 		pr_warn("OPAL: memory console version is invalid\n");
119 		return;
120 	}
121 
122 	/* Report maximum size */
123 	opal_msglog_attr.size =  be32_to_cpu(mc->ibuf_size) +
124 		be32_to_cpu(mc->obuf_size);
125 
126 	opal_memcons = mc;
127 }
128 
129 void __init opal_msglog_sysfs_init(void)
130 {
131 	if (!opal_memcons) {
132 		pr_warn("OPAL: message log initialisation failed, not creating sysfs entry\n");
133 		return;
134 	}
135 
136 	if (sysfs_create_bin_file(opal_kobj, &opal_msglog_attr) != 0)
137 		pr_warn("OPAL: sysfs file creation failed\n");
138 }
139