1/*
2 *  c 2001 PPC 64 Team, IBM Corp
3 *
4 *      This program is free software; you can redistribute it and/or
5 *      modify it under the terms of the GNU General Public License
6 *      as published by the Free Software Foundation; either version
7 *      2 of the License, or (at your option) any later version.
8 *
9 * scan-log-data driver for PPC64  Todd Inglett <tinglett@vnet.ibm.com>
10 *
11 * When ppc64 hardware fails the service processor dumps internal state
12 * of the system.  After a reboot the operating system can access a dump
13 * of this data using this driver.  A dump exists if the device-tree
14 * /chosen/ibm,scan-log-data property exists.
15 *
16 * This driver exports /proc/powerpc/scan-log-dump which can be read.
17 * The driver supports only sequential reads.
18 *
19 * The driver looks at a write to the driver for the single word "reset".
20 * If given, the driver will reset the scanlog so the platform can free it.
21 */
22
23#include <linux/module.h>
24#include <linux/types.h>
25#include <linux/errno.h>
26#include <linux/proc_fs.h>
27#include <linux/init.h>
28#include <linux/delay.h>
29#include <linux/slab.h>
30#include <asm/uaccess.h>
31#include <asm/rtas.h>
32#include <asm/prom.h>
33
34#define MODULE_VERS "1.0"
35#define MODULE_NAME "scanlog"
36
37/* Status returns from ibm,scan-log-dump */
38#define SCANLOG_COMPLETE 0
39#define SCANLOG_HWERROR -1
40#define SCANLOG_CONTINUE 1
41
42
43static unsigned int ibm_scan_log_dump;			/* RTAS token */
44static unsigned int *scanlog_buffer;			/* The data buffer */
45
46static ssize_t scanlog_read(struct file *file, char __user *buf,
47			    size_t count, loff_t *ppos)
48{
49	unsigned int *data = scanlog_buffer;
50	int status;
51	unsigned long len, off;
52	unsigned int wait_time;
53
54	if (count > RTAS_DATA_BUF_SIZE)
55		count = RTAS_DATA_BUF_SIZE;
56
57	if (count < 1024) {
58		/* This is the min supported by this RTAS call.  Rather
59		 * than do all the buffering we insist the user code handle
60		 * larger reads.  As long as cp works... :)
61		 */
62		printk(KERN_ERR "scanlog: cannot perform a small read (%ld)\n", count);
63		return -EINVAL;
64	}
65
66	if (!access_ok(VERIFY_WRITE, buf, count))
67		return -EFAULT;
68
69	for (;;) {
70		wait_time = 500;	/* default wait if no data */
71		spin_lock(&rtas_data_buf_lock);
72		memcpy(rtas_data_buf, data, RTAS_DATA_BUF_SIZE);
73		status = rtas_call(ibm_scan_log_dump, 2, 1, NULL,
74				   (u32) __pa(rtas_data_buf), (u32) count);
75		memcpy(data, rtas_data_buf, RTAS_DATA_BUF_SIZE);
76		spin_unlock(&rtas_data_buf_lock);
77
78		pr_debug("scanlog: status=%d, data[0]=%x, data[1]=%x, " \
79			 "data[2]=%x\n", status, data[0], data[1], data[2]);
80		switch (status) {
81		    case SCANLOG_COMPLETE:
82			pr_debug("scanlog: hit eof\n");
83			return 0;
84		    case SCANLOG_HWERROR:
85			pr_debug("scanlog: hardware error reading data\n");
86			return -EIO;
87		    case SCANLOG_CONTINUE:
88			/* We may or may not have data yet */
89			len = data[1];
90			off = data[2];
91			if (len > 0) {
92				if (copy_to_user(buf, ((char *)data)+off, len))
93					return -EFAULT;
94				return len;
95			}
96			/* Break to sleep default time */
97			break;
98		    default:
99			/* Assume extended busy */
100			wait_time = rtas_busy_delay_time(status);
101			if (!wait_time) {
102				printk(KERN_ERR "scanlog: unknown error " \
103				       "from rtas: %d\n", status);
104				return -EIO;
105			}
106		}
107		/* Apparently no data yet.  Wait and try again. */
108		msleep_interruptible(wait_time);
109	}
110	/*NOTREACHED*/
111}
112
113static ssize_t scanlog_write(struct file * file, const char __user * buf,
114			     size_t count, loff_t *ppos)
115{
116	char stkbuf[20];
117	int status;
118
119	if (count > 19) count = 19;
120	if (copy_from_user (stkbuf, buf, count)) {
121		return -EFAULT;
122	}
123	stkbuf[count] = 0;
124
125	if (buf) {
126		if (strncmp(stkbuf, "reset", 5) == 0) {
127			pr_debug("scanlog: reset scanlog\n");
128			status = rtas_call(ibm_scan_log_dump, 2, 1, NULL, 0, 0);
129			pr_debug("scanlog: rtas returns %d\n", status);
130		}
131	}
132	return count;
133}
134
135static int scanlog_open(struct inode * inode, struct file * file)
136{
137	unsigned int *data = scanlog_buffer;
138
139	if (data[0] != 0) {
140		/* This imperfect test stops a second copy of the
141		 * data (or a reset while data is being copied)
142		 */
143		return -EBUSY;
144	}
145
146	data[0] = 0;	/* re-init so we restart the scan */
147
148	return 0;
149}
150
151static int scanlog_release(struct inode * inode, struct file * file)
152{
153	unsigned int *data = scanlog_buffer;
154
155	data[0] = 0;
156	return 0;
157}
158
159const struct file_operations scanlog_fops = {
160	.owner		= THIS_MODULE,
161	.read		= scanlog_read,
162	.write		= scanlog_write,
163	.open		= scanlog_open,
164	.release	= scanlog_release,
165	.llseek		= noop_llseek,
166};
167
168static int __init scanlog_init(void)
169{
170	struct proc_dir_entry *ent;
171	int err = -ENOMEM;
172
173	ibm_scan_log_dump = rtas_token("ibm,scan-log-dump");
174	if (ibm_scan_log_dump == RTAS_UNKNOWN_SERVICE)
175		return -ENODEV;
176
177	/* Ideally we could allocate a buffer < 4G */
178	scanlog_buffer = kzalloc(RTAS_DATA_BUF_SIZE, GFP_KERNEL);
179	if (!scanlog_buffer)
180		goto err;
181
182	ent = proc_create("powerpc/rtas/scan-log-dump", S_IRUSR, NULL,
183			  &scanlog_fops);
184	if (!ent)
185		goto err;
186	return 0;
187err:
188	kfree(scanlog_buffer);
189	return err;
190}
191
192static void __exit scanlog_cleanup(void)
193{
194	remove_proc_entry("powerpc/rtas/scan-log-dump", NULL);
195	kfree(scanlog_buffer);
196}
197
198module_init(scanlog_init);
199module_exit(scanlog_cleanup);
200MODULE_LICENSE("GPL");
201