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>
17 /* OPAL in-memory console. Defined in OPAL source at core/console.c */
20 #define MEMCONS_MAGIC 0x6630696567726173L
26 #define MEMCONS_OUT_POS_WRAP 0x80000000u
27 #define MEMCONS_OUT_POS_MASK 0x00ffffffu
32 static struct memcons *opal_memcons = NULL;
34 ssize_t memcons_copy(struct memcons *mc, char *to, loff_t pos, size_t count)
38 size_t first_read = 0;
39 uint32_t out_pos, avail;
44 out_pos = be32_to_cpu(READ_ONCE(mc->out_pos));
46 /* Now we've read out_pos, put a barrier in before reading the new
47 * data it points to in conbuf. */
50 conbuf = phys_to_virt(be64_to_cpu(mc->obuf_phys));
52 /* When the buffer has wrapped, read from the out_pos marker to the end
53 * of the buffer, and then read the remaining data as in the un-wrapped
55 if (out_pos & MEMCONS_OUT_POS_WRAP) {
57 out_pos &= MEMCONS_OUT_POS_MASK;
58 avail = be32_to_cpu(mc->obuf_size) - out_pos;
60 ret = memory_read_from_buffer(to, count, &pos,
61 conbuf + out_pos, avail);
75 /* Sanity check. The firmware should not do this to us. */
76 if (out_pos > be32_to_cpu(mc->obuf_size)) {
77 pr_err("OPAL: memory console corruption. Aborting read.\n");
81 ret = memory_read_from_buffer(to, count, &pos, conbuf, out_pos);
91 ssize_t opal_msglog_copy(char *to, loff_t pos, size_t count)
93 return memcons_copy(opal_memcons, to, pos, count);
96 static ssize_t opal_msglog_read(struct file *file, struct kobject *kobj,
97 struct bin_attribute *bin_attr, char *to,
98 loff_t pos, size_t count)
100 return opal_msglog_copy(to, pos, count);
103 static struct bin_attribute opal_msglog_attr = {
104 .attr = {.name = "msglog", .mode = 0400},
105 .read = opal_msglog_read
108 struct memcons *__init memcons_init(struct device_node *node, const char *mc_prop_name)
113 if (of_property_read_u64(node, mc_prop_name, &mcaddr)) {
114 pr_warn("%s property not found, no message log\n",
119 mc = phys_to_virt(mcaddr);
121 pr_warn("memory console address is invalid\n");
125 if (be64_to_cpu(mc->magic) != MEMCONS_MAGIC) {
126 pr_warn("memory console version is invalid\n");
136 u32 __init memcons_get_size(struct memcons *mc)
138 return be32_to_cpu(mc->ibuf_size) + be32_to_cpu(mc->obuf_size);
141 void __init opal_msglog_init(void)
143 opal_memcons = memcons_init(opal_node, "ibm,opal-memcons");
145 pr_warn("OPAL: memcons failed to load from ibm,opal-memcons\n");
149 opal_msglog_attr.size = memcons_get_size(opal_memcons);
152 void __init opal_msglog_sysfs_init(void)
155 pr_warn("OPAL: message log initialisation failed, not creating sysfs entry\n");
159 if (sysfs_create_bin_file(opal_kobj, &opal_msglog_attr) != 0)
160 pr_warn("OPAL: sysfs file creation failed\n");