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#include "powernv.h"
16
17/* OPAL in-memory console. Defined in OPAL source at core/console.c */
18struct memcons {
19	__be64 magic;
20#define MEMCONS_MAGIC	0x6630696567726173L
21	__be64 obuf_phys;
22	__be64 ibuf_phys;
23	__be32 obuf_size;
24	__be32 ibuf_size;
25	__be32 out_pos;
26#define MEMCONS_OUT_POS_WRAP	0x80000000u
27#define MEMCONS_OUT_POS_MASK	0x00ffffffu
28	__be32 in_prod;
29	__be32 in_cons;
30};
31
32static struct memcons *opal_memcons = NULL;
33
34ssize_t memcons_copy(struct memcons *mc, char *to, loff_t pos, size_t count)
35{
36	const char *conbuf;
37	ssize_t ret;
38	size_t first_read = 0;
39	uint32_t out_pos, avail;
40
41	if (!mc)
42		return -ENODEV;
43
44	out_pos = be32_to_cpu(READ_ONCE(mc->out_pos));
45
46	/* Now we've read out_pos, put a barrier in before reading the new
47	 * data it points to in conbuf. */
48	smp_rmb();
49
50	conbuf = phys_to_virt(be64_to_cpu(mc->obuf_phys));
51
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
54	 * case. */
55	if (out_pos & MEMCONS_OUT_POS_WRAP) {
56
57		out_pos &= MEMCONS_OUT_POS_MASK;
58		avail = be32_to_cpu(mc->obuf_size) - out_pos;
59
60		ret = memory_read_from_buffer(to, count, &pos,
61				conbuf + out_pos, avail);
62
63		if (ret < 0)
64			goto out;
65
66		first_read = ret;
67		to += first_read;
68		count -= first_read;
69		pos -= avail;
70
71		if (count <= 0)
72			goto out;
73	}
74
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");
78		return -EINVAL;
79	}
80
81	ret = memory_read_from_buffer(to, count, &pos, conbuf, out_pos);
82
83	if (ret < 0)
84		goto out;
85
86	ret += first_read;
87out:
88	return ret;
89}
90
91ssize_t opal_msglog_copy(char *to, loff_t pos, size_t count)
92{
93	return memcons_copy(opal_memcons, to, pos, count);
94}
95
96static 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)
99{
100	return opal_msglog_copy(to, pos, count);
101}
102
103static struct bin_attribute opal_msglog_attr = {
104	.attr = {.name = "msglog", .mode = 0400},
105	.read = opal_msglog_read
106};
107
108struct memcons *__init memcons_init(struct device_node *node, const char *mc_prop_name)
109{
110	u64 mcaddr;
111	struct memcons *mc;
112
113	if (of_property_read_u64(node, mc_prop_name, &mcaddr)) {
114		pr_warn("%s property not found, no message log\n",
115			mc_prop_name);
116		goto out_err;
117	}
118
119	mc = phys_to_virt(mcaddr);
120	if (!mc) {
121		pr_warn("memory console address is invalid\n");
122		goto out_err;
123	}
124
125	if (be64_to_cpu(mc->magic) != MEMCONS_MAGIC) {
126		pr_warn("memory console version is invalid\n");
127		goto out_err;
128	}
129
130	return mc;
131
132out_err:
133	return NULL;
134}
135
136u32 __init memcons_get_size(struct memcons *mc)
137{
138	return be32_to_cpu(mc->ibuf_size) + be32_to_cpu(mc->obuf_size);
139}
140
141void __init opal_msglog_init(void)
142{
143	opal_memcons = memcons_init(opal_node, "ibm,opal-memcons");
144	if (!opal_memcons) {
145		pr_warn("OPAL: memcons failed to load from ibm,opal-memcons\n");
146		return;
147	}
148
149	opal_msglog_attr.size = memcons_get_size(opal_memcons);
150}
151
152void __init opal_msglog_sysfs_init(void)
153{
154	if (!opal_memcons) {
155		pr_warn("OPAL: message log initialisation failed, not creating sysfs entry\n");
156		return;
157	}
158
159	if (sysfs_create_bin_file(opal_kobj, &opal_msglog_attr) != 0)
160		pr_warn("OPAL: sysfs file creation failed\n");
161}
162