2 * PowerNV OPAL in-memory console interface
4 * Copyright 2014 IBM Corp.
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.
14 #include <linux/debugfs.h>
16 #include <linux/types.h>
17 #include <asm/barrier.h>
19 /* OPAL in-memory console. Defined in OPAL source at core/console.c */
22 #define MEMCONS_MAGIC 0x6630696567726173L
28 #define MEMCONS_OUT_POS_WRAP 0x80000000u
29 #define MEMCONS_OUT_POS_MASK 0x00ffffffu
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)
38 struct memcons *mc = bin_attr->private;
40 size_t ret, first_read = 0;
41 uint32_t out_pos, avail;
46 out_pos = be32_to_cpu(ACCESS_ONCE(mc->out_pos));
48 /* Now we've read out_pos, put a barrier in before reading the new
49 * data it points to in conbuf. */
52 conbuf = phys_to_virt(be64_to_cpu(mc->obuf_phys));
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
57 if (out_pos & MEMCONS_OUT_POS_WRAP) {
59 out_pos &= MEMCONS_OUT_POS_MASK;
60 avail = be32_to_cpu(mc->obuf_size) - out_pos;
62 ret = memory_read_from_buffer(to, count, &pos,
63 conbuf + out_pos, avail);
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");
80 ret = memory_read_from_buffer(to, count, &pos, conbuf, out_pos);
90 static struct bin_attribute opal_msglog_attr = {
91 .attr = {.name = "msglog", .mode = 0444},
92 .read = opal_msglog_read
95 void __init opal_msglog_init(void)
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");
105 mc = phys_to_virt(mcaddr);
107 pr_warn("OPAL: memory console address is invalid\n");
111 if (be64_to_cpu(mc->magic) != MEMCONS_MAGIC) {
112 pr_warn("OPAL: memory console version is invalid\n");
116 opal_msglog_attr.private = mc;
118 if (sysfs_create_bin_file(opal_kobj, &opal_msglog_attr) != 0)
119 pr_warn("OPAL: sysfs file creation failed\n");