diff options
Diffstat (limited to 'drivers/base/power')
| -rw-r--r-- | drivers/base/power/Makefile | 1 | ||||
| -rw-r--r-- | drivers/base/power/trace.c | 228 |
2 files changed, 229 insertions, 0 deletions
diff --git a/drivers/base/power/Makefile b/drivers/base/power/Makefile index ceeeba2c56c..91f230939c1 100644 --- a/drivers/base/power/Makefile +++ b/drivers/base/power/Makefile @@ -1,5 +1,6 @@ obj-y := shutdown.o obj-$(CONFIG_PM) += main.o suspend.o resume.o runtime.o sysfs.o +obj-$(CONFIG_PM_TRACE) += trace.o ifeq ($(CONFIG_DEBUG_DRIVER),y) EXTRA_CFLAGS += -DDEBUG diff --git a/drivers/base/power/trace.c b/drivers/base/power/trace.c new file mode 100644 index 00000000000..a9ab30fefff --- /dev/null +++ b/drivers/base/power/trace.c @@ -0,0 +1,228 @@ +/* + * drivers/base/power/trace.c + * + * Copyright (C) 2006 Linus Torvalds + * + * Trace facility for suspend/resume problems, when none of the + * devices may be working. + */ + +#include <linux/resume-trace.h> +#include <linux/rtc.h> + +#include <asm/rtc.h> + +#include "power.h" + +/* + * 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) + +#define DEVSEED (7919) + +static unsigned int dev_hash_value; + +static int set_magic_time(unsigned int user, unsigned int file, unsigned int device) +{ + unsigned int n = user + USERHASH*(file + FILEHASH*device); + + // 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 + }; + + 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; +} + +static unsigned int read_magic_time(void) +{ + struct rtc_time time; + unsigned int val; + + 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; +} + +/* + * 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; +} + +void set_trace_device(struct device *dev) +{ + dev_hash_value = hash_string(DEVSEED, dev->bus_id, DEVHASH); +} + +/* + * 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; + + 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); +} + +extern char __tracedata_start, __tracedata_end; +static int show_file_hash(unsigned int value) +{ + int match; + char *tracedata; + + 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; +} + +static int show_dev_hash(unsigned int value) +{ + int match = 0; + struct list_head * entry = dpm_active.prev; + + 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; +} + +static unsigned int hash_value_early_read; + +static int early_resume_init(void) +{ + hash_value_early_read = read_magic_time(); + return 0; +} + +static int late_resume_init(void) +{ + unsigned int val = hash_value_early_read; + unsigned int user, file, dev; + + user = val % USERHASH; + val = val / USERHASH; + file = val % FILEHASH; + val = val / FILEHASH; + dev = val /* % DEVHASH */; + + printk(" Magic number: %d:%d:%d\n", user, file, dev); + show_file_hash(file); + show_dev_hash(dev); + return 0; +} + +core_initcall(early_resume_init); +late_initcall(late_resume_init); |