1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * PowerNV OPAL in-memory console interface
5 * Copyright 2014 IBM Corp.
10 #include <linux/debugfs.h>
12 #include <linux/types.h>
13 #include <asm/barrier.h>
15 /* OPAL in-memory console. Defined in OPAL source at core/console.c */
18 #define MEMCONS_MAGIC 0x6630696567726173L
24 #define MEMCONS_OUT_POS_WRAP 0x80000000u
25 #define MEMCONS_OUT_POS_MASK 0x00ffffffu
30 static struct memcons *opal_memcons = NULL;
32 ssize_t memcons_copy(struct memcons *mc, char *to, loff_t pos, size_t count)
36 size_t first_read = 0;
37 uint32_t out_pos, avail;
42 out_pos = be32_to_cpu(READ_ONCE(mc->out_pos));
44 /* Now we've read out_pos, put a barrier in before reading the new
45 * data it points to in conbuf. */
48 conbuf = phys_to_virt(be64_to_cpu(mc->obuf_phys));
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
53 if (out_pos & MEMCONS_OUT_POS_WRAP) {
55 out_pos &= MEMCONS_OUT_POS_MASK;
56 avail = be32_to_cpu(mc->obuf_size) - out_pos;
58 ret = memory_read_from_buffer(to, count, &pos,
59 conbuf + out_pos, avail);
73 /* Sanity check. The firmware should not do this to us. */
74 if (out_pos > be32_to_cpu(mc->obuf_size)) {
75 pr_err("OPAL: memory console corruption. Aborting read.\n");
79 ret = memory_read_from_buffer(to, count, &pos, conbuf, out_pos);
89 ssize_t opal_msglog_copy(char *to, loff_t pos, size_t count)
91 return memcons_copy(opal_memcons, to, pos, count);
94 static ssize_t opal_msglog_read(struct file *file, struct kobject *kobj,
95 struct bin_attribute *bin_attr, char *to,
96 loff_t pos, size_t count)
98 return opal_msglog_copy(to, pos, count);
101 static struct bin_attribute opal_msglog_attr = {
102 .attr = {.name = "msglog", .mode = 0400},
103 .read = opal_msglog_read
106 struct memcons *memcons_init(struct device_node *node, const char *mc_prop_name)
111 if (of_property_read_u64(node, mc_prop_name, &mcaddr)) {
112 pr_warn("%s property not found, no message log\n",
117 mc = phys_to_virt(mcaddr);
119 pr_warn("memory console address is invalid\n");
123 if (be64_to_cpu(mc->magic) != MEMCONS_MAGIC) {
124 pr_warn("memory console version is invalid\n");
134 u32 memcons_get_size(struct memcons *mc)
136 return be32_to_cpu(mc->ibuf_size) + be32_to_cpu(mc->obuf_size);
139 void __init opal_msglog_init(void)
141 opal_memcons = memcons_init(opal_node, "ibm,opal-memcons");
143 pr_warn("OPAL: memcons failed to load from ibm,opal-memcons\n");
147 opal_msglog_attr.size = memcons_get_size(opal_memcons);
150 void __init opal_msglog_sysfs_init(void)
153 pr_warn("OPAL: message log initialisation failed, not creating sysfs entry\n");
157 if (sysfs_create_bin_file(opal_kobj, &opal_msglog_attr) != 0)
158 pr_warn("OPAL: sysfs file creation failed\n");