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Add some basic resume trace facilities
Considering that there isn't a lot of hw we can depend on during resume, this is about as good as it gets. This is x86-only for now, although the basic concept (and most of the code) will certainly work on almost any platform. Signed-off-by: Linus Torvalds <[email protected]>
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Jun 24, 2006
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/* | ||
* drivers/base/power/trace.c | ||
* | ||
* Copyright (C) 2006 Linus Torvalds | ||
* | ||
* Trace facility for suspend/resume problems, when none of the | ||
* devices may be working. | ||
*/ | ||
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#include <linux/resume-trace.h> | ||
#include <linux/rtc.h> | ||
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#include <asm/rtc.h> | ||
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#include "power.h" | ||
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/* | ||
* Horrid, horrid, horrid. | ||
* | ||
* It turns out that the _only_ piece of hardware that actually | ||
* keeps its value across a hard boot (and, more importantly, the | ||
* POST init sequence) is literally the realtime clock. | ||
* | ||
* Never mind that an RTC chip has 114 bytes (and often a whole | ||
* other bank of an additional 128 bytes) of nice SRAM that is | ||
* _designed_ to keep data - the POST will clear it. So we literally | ||
* can just use the few bytes of actual time data, which means that | ||
* we're really limited. | ||
* | ||
* It means, for example, that we can't use the seconds at all | ||
* (since the time between the hang and the boot might be more | ||
* than a minute), and we'd better not depend on the low bits of | ||
* the minutes either. | ||
* | ||
* There are the wday fields etc, but I wouldn't guarantee those | ||
* are dependable either. And if the date isn't valid, either the | ||
* hw or POST will do strange things. | ||
* | ||
* So we're left with: | ||
* - year: 0-99 | ||
* - month: 0-11 | ||
* - day-of-month: 1-28 | ||
* - hour: 0-23 | ||
* - min: (0-30)*2 | ||
* | ||
* Giving us a total range of 0-16128000 (0xf61800), ie less | ||
* than 24 bits of actual data we can save across reboots. | ||
* | ||
* And if your box can't boot in less than three minutes, | ||
* you're screwed. | ||
* | ||
* Now, almost 24 bits of data is pitifully small, so we need | ||
* to be pretty dense if we want to use it for anything nice. | ||
* What we do is that instead of saving off nice readable info, | ||
* we save off _hashes_ of information that we can hopefully | ||
* regenerate after the reboot. | ||
* | ||
* In particular, this means that we might be unlucky, and hit | ||
* a case where we have a hash collision, and we end up not | ||
* being able to tell for certain exactly which case happened. | ||
* But that's hopefully unlikely. | ||
* | ||
* What we do is to take the bits we can fit, and split them | ||
* into three parts (16*997*1009 = 16095568), and use the values | ||
* for: | ||
* - 0-15: user-settable | ||
* - 0-996: file + line number | ||
* - 0-1008: device | ||
*/ | ||
#define USERHASH (16) | ||
#define FILEHASH (997) | ||
#define DEVHASH (1009) | ||
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#define DEVSEED (7919) | ||
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static unsigned int dev_hash_value; | ||
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static int set_magic_time(unsigned int user, unsigned int file, unsigned int device) | ||
{ | ||
unsigned int n = user + USERHASH*(file + FILEHASH*device); | ||
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// June 7th, 2006 | ||
static struct rtc_time time = { | ||
.tm_sec = 0, | ||
.tm_min = 0, | ||
.tm_hour = 0, | ||
.tm_mday = 7, | ||
.tm_mon = 5, // June - counting from zero | ||
.tm_year = 106, | ||
.tm_wday = 3, | ||
.tm_yday = 160, | ||
.tm_isdst = 1 | ||
}; | ||
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time.tm_year = (n % 100); | ||
n /= 100; | ||
time.tm_mon = (n % 12); | ||
n /= 12; | ||
time.tm_mday = (n % 28) + 1; | ||
n /= 28; | ||
time.tm_hour = (n % 24); | ||
n /= 24; | ||
time.tm_min = (n % 20) * 3; | ||
n /= 20; | ||
set_rtc_time(&time); | ||
return n ? -1 : 0; | ||
} | ||
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static unsigned int read_magic_time(void) | ||
{ | ||
struct rtc_time time; | ||
unsigned int val; | ||
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get_rtc_time(&time); | ||
printk("Time: %2d:%02d:%02d Date: %02d/%02d/%02d\n", | ||
time.tm_hour, time.tm_min, time.tm_sec, | ||
time.tm_mon, time.tm_mday, time.tm_year); | ||
val = time.tm_year; /* 100 years */ | ||
if (val > 100) | ||
val -= 100; | ||
val += time.tm_mon * 100; /* 12 months */ | ||
val += (time.tm_mday-1) * 100 * 12; /* 28 month-days */ | ||
val += time.tm_hour * 100 * 12 * 28; /* 24 hours */ | ||
val += (time.tm_min / 3) * 100 * 12 * 28 * 24; /* 20 3-minute intervals */ | ||
return val; | ||
} | ||
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/* | ||
* This is just the sdbm hash function with a user-supplied | ||
* seed and final size parameter. | ||
*/ | ||
static unsigned int hash_string(unsigned int seed, const char *data, unsigned int mod) | ||
{ | ||
unsigned char c; | ||
while ((c = *data++) != 0) { | ||
seed = (seed << 16) + (seed << 6) - seed + c; | ||
} | ||
return seed % mod; | ||
} | ||
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void set_trace_device(struct device *dev) | ||
{ | ||
dev_hash_value = hash_string(DEVSEED, dev->bus_id, DEVHASH); | ||
} | ||
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/* | ||
* We could just take the "tracedata" index into the .tracedata | ||
* section instead. Generating a hash of the data gives us a | ||
* chance to work across kernel versions, and perhaps more | ||
* importantly it also gives us valid/invalid check (ie we will | ||
* likely not give totally bogus reports - if the hash matches, | ||
* it's not any guarantee, but it's a high _likelihood_ that | ||
* the match is valid). | ||
*/ | ||
void generate_resume_trace(void *tracedata, unsigned int user) | ||
{ | ||
unsigned short lineno = *(unsigned short *)tracedata; | ||
const char *file = *(const char **)(tracedata + 2); | ||
unsigned int user_hash_value, file_hash_value; | ||
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user_hash_value = user % USERHASH; | ||
file_hash_value = hash_string(lineno, file, FILEHASH); | ||
set_magic_time(user_hash_value, file_hash_value, dev_hash_value); | ||
} | ||
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extern char __tracedata_start, __tracedata_end; | ||
static int show_file_hash(unsigned int value) | ||
{ | ||
int match; | ||
char *tracedata; | ||
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match = 0; | ||
for (tracedata = &__tracedata_start ; tracedata < &__tracedata_end ; tracedata += 6) { | ||
unsigned short lineno = *(unsigned short *)tracedata; | ||
const char *file = *(const char **)(tracedata + 2); | ||
unsigned int hash = hash_string(lineno, file, FILEHASH); | ||
if (hash != value) | ||
continue; | ||
printk(" hash matches %s:%u\n", file, lineno); | ||
match++; | ||
} | ||
return match; | ||
} | ||
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static int show_dev_hash(unsigned int value) | ||
{ | ||
int match = 0; | ||
struct list_head * entry = dpm_active.prev; | ||
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while (entry != &dpm_active) { | ||
struct device * dev = to_device(entry); | ||
unsigned int hash = hash_string(DEVSEED, dev->bus_id, DEVHASH); | ||
if (hash == value) { | ||
printk(" hash matches device %s\n", dev->bus_id); | ||
match++; | ||
} | ||
entry = entry->prev; | ||
} | ||
return match; | ||
} | ||
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static unsigned int hash_value_early_read; | ||
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static int early_resume_init(void) | ||
{ | ||
hash_value_early_read = read_magic_time(); | ||
return 0; | ||
} | ||
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static int late_resume_init(void) | ||
{ | ||
unsigned int val = hash_value_early_read; | ||
unsigned int user, file, dev; | ||
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user = val % USERHASH; | ||
val = val / USERHASH; | ||
file = val % FILEHASH; | ||
val = val / FILEHASH; | ||
dev = val /* % DEVHASH */; | ||
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printk(" Magic number: %d:%d:%d\n", user, file, dev); | ||
show_file_hash(file); | ||
show_dev_hash(dev); | ||
return 0; | ||
} | ||
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core_initcall(early_resume_init); | ||
late_initcall(late_resume_init); |
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Original file line number | Diff line number | Diff line change |
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#ifndef RESUME_TRACE_H | ||
#define RESUME_TRACE_H | ||
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#ifdef CONFIG_PM_TRACE | ||
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struct device; | ||
extern void set_trace_device(struct device *); | ||
extern void generate_resume_trace(void *tracedata, unsigned int user); | ||
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#define TRACE_DEVICE(dev) set_trace_device(dev) | ||
#define TRACE_RESUME(user) do { \ | ||
void *tracedata; \ | ||
asm volatile("movl $1f,%0\n" \ | ||
".section .tracedata,\"a\"\n" \ | ||
"1:\t.word %c1\n" \ | ||
"\t.long %c2\n" \ | ||
".previous" \ | ||
:"=r" (tracedata) \ | ||
: "i" (__LINE__), "i" (__FILE__)); \ | ||
generate_resume_trace(tracedata, user); \ | ||
} while (0) | ||
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#else | ||
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#define TRACE_DEVICE(dev) do { } while (0) | ||
#define TRACE_RESUME(dev) do { } while (0) | ||
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#endif | ||
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#endif |
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