opal-msglog.c

  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				const 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 __ro_after_init = {
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}