From 2b91d7ba805279f3f871f95d5d49c6c1b7d6b879 Mon Sep 17 00:00:00 2001 From: Zheng Da Date: Mon, 12 Jul 2010 09:47:31 +0200 Subject: Use Linux's udelay and ndelay. It's not very precise to implement udelay and ndelay with loops in the user space, but should be enough. --- libdde_linux26/lib/src/init/calibrate.c | 182 ++++++++++++++++++++++++++++++++ 1 file changed, 182 insertions(+) create mode 100644 libdde_linux26/lib/src/init/calibrate.c (limited to 'libdde_linux26/lib/src/init') diff --git a/libdde_linux26/lib/src/init/calibrate.c b/libdde_linux26/lib/src/init/calibrate.c new file mode 100644 index 00000000..aede8e53 --- /dev/null +++ b/libdde_linux26/lib/src/init/calibrate.c @@ -0,0 +1,182 @@ +/* calibrate.c: default delay calibration + * + * Excised from init/main.c + * Copyright (C) 1991, 1992 Linus Torvalds + */ + +#include +#include +#include +#include +#include +#include + +unsigned long loops_per_jiffy = (1<<12); +EXPORT_SYMBOL(loops_per_jiffy); + +unsigned long lpj_fine; +unsigned long preset_lpj; +static int __init lpj_setup(char *str) +{ + preset_lpj = simple_strtoul(str,NULL,0); + return 1; +} + +__setup("lpj=", lpj_setup); + +#ifdef ARCH_HAS_READ_CURRENT_TIMER + +/* This routine uses the read_current_timer() routine and gets the + * loops per jiffy directly, instead of guessing it using delay(). + * Also, this code tries to handle non-maskable asynchronous events + * (like SMIs) + */ +#define DELAY_CALIBRATION_TICKS ((HZ < 100) ? 1 : (HZ/100)) +#define MAX_DIRECT_CALIBRATION_RETRIES 5 + +static unsigned long __cpuinit calibrate_delay_direct(void) +{ + unsigned long pre_start, start, post_start; + unsigned long pre_end, end, post_end; + unsigned long start_jiffies; + unsigned long timer_rate_min, timer_rate_max; + unsigned long good_timer_sum = 0; + unsigned long good_timer_count = 0; + int i; + + if (read_current_timer(&pre_start) < 0 ) + return 0; + + /* + * A simple loop like + * while ( jiffies < start_jiffies+1) + * start = read_current_timer(); + * will not do. As we don't really know whether jiffy switch + * happened first or timer_value was read first. And some asynchronous + * event can happen between these two events introducing errors in lpj. + * + * So, we do + * 1. pre_start <- When we are sure that jiffy switch hasn't happened + * 2. check jiffy switch + * 3. start <- timer value before or after jiffy switch + * 4. post_start <- When we are sure that jiffy switch has happened + * + * Note, we don't know anything about order of 2 and 3. + * Now, by looking at post_start and pre_start difference, we can + * check whether any asynchronous event happened or not + */ + + for (i = 0; i < MAX_DIRECT_CALIBRATION_RETRIES; i++) { + pre_start = 0; + read_current_timer(&start); + start_jiffies = jiffies; + while (jiffies <= (start_jiffies + 1)) { + pre_start = start; + read_current_timer(&start); + } + read_current_timer(&post_start); + + pre_end = 0; + end = post_start; + while (jiffies <= + (start_jiffies + 1 + DELAY_CALIBRATION_TICKS)) { + pre_end = end; + read_current_timer(&end); + } + read_current_timer(&post_end); + + timer_rate_max = (post_end - pre_start) / + DELAY_CALIBRATION_TICKS; + timer_rate_min = (pre_end - post_start) / + DELAY_CALIBRATION_TICKS; + + /* + * If the upper limit and lower limit of the timer_rate is + * >= 12.5% apart, redo calibration. + */ + if (pre_start != 0 && pre_end != 0 && + (timer_rate_max - timer_rate_min) < (timer_rate_max >> 3)) { + good_timer_count++; + good_timer_sum += timer_rate_max; + } + } + + if (good_timer_count) + return (good_timer_sum/good_timer_count); + + printk(KERN_WARNING "calibrate_delay_direct() failed to get a good " + "estimate for loops_per_jiffy.\nProbably due to long platform interrupts. Consider using \"lpj=\" boot option.\n"); + return 0; +} +#else +static unsigned long __cpuinit calibrate_delay_direct(void) {return 0;} +#endif + +/* + * This is the number of bits of precision for the loops_per_jiffy. Each + * bit takes on average 1.5/HZ seconds. This (like the original) is a little + * better than 1% + * For the boot cpu we can skip the delay calibration and assign it a value + * calculated based on the timer frequency. + * For the rest of the CPUs we cannot assume that the timer frequency is same as + * the cpu frequency, hence do the calibration for those. + */ +#define LPS_PREC 8 + +void __cpuinit calibrate_delay(void) +{ + unsigned long ticks, loopbit; + int lps_precision = LPS_PREC; + + if (preset_lpj) { + loops_per_jiffy = preset_lpj; + printk(KERN_INFO + "Calibrating delay loop (skipped) preset value.. "); + } else if ((smp_processor_id() == 0) && lpj_fine) { + loops_per_jiffy = lpj_fine; + printk(KERN_INFO + "Calibrating delay loop (skipped), " + "value calculated using timer frequency.. "); + } else if ((loops_per_jiffy = calibrate_delay_direct()) != 0) { + printk(KERN_INFO + "Calibrating delay using timer specific routine.. "); + } else { + loops_per_jiffy = (1<<12); + + printk(KERN_INFO "Calibrating delay loop... "); + while ((loops_per_jiffy <<= 1) != 0) { + /* wait for "start of" clock tick */ + ticks = jiffies; + while (ticks == jiffies) + /* nothing */; + /* Go .. */ + ticks = jiffies; + __delay(loops_per_jiffy); + ticks = jiffies - ticks; + if (ticks) + break; + } + + /* + * Do a binary approximation to get loops_per_jiffy set to + * equal one clock (up to lps_precision bits) + */ + loops_per_jiffy >>= 1; + loopbit = loops_per_jiffy; + while (lps_precision-- && (loopbit >>= 1)) { + loops_per_jiffy |= loopbit; + ticks = jiffies; + while (ticks == jiffies) + /* nothing */; + ticks = jiffies; + __delay(loops_per_jiffy); + if (jiffies != ticks) /* longer than 1 tick */ + loops_per_jiffy &= ~loopbit; + } + } + printk(KERN_CONT "%lu.%02lu BogoMIPS (lpj=%lu)\n", + loops_per_jiffy/(500000/HZ), + (loops_per_jiffy/(5000/HZ)) % 100, loops_per_jiffy); +} + +core_initcall(calibrate_delay); -- cgit v1.2.3 From 91af4ed54bbdb3a2cae9606eb69ebbaddff5602c Mon Sep 17 00:00:00 2001 From: Zheng Da Date: Mon, 12 Jul 2010 22:46:28 +0200 Subject: calibrate the delay loop several times. It's necessary when we do it in the user space, as that the CPU switches to other processes and the result is too imprecise. --- libdde_linux26/lib/src/init/calibrate.c | 78 ++++++++++++++++++++------------- 1 file changed, 48 insertions(+), 30 deletions(-) (limited to 'libdde_linux26/lib/src/init') diff --git a/libdde_linux26/lib/src/init/calibrate.c b/libdde_linux26/lib/src/init/calibrate.c index aede8e53..687da473 100644 --- a/libdde_linux26/lib/src/init/calibrate.c +++ b/libdde_linux26/lib/src/init/calibrate.c @@ -123,11 +123,50 @@ static unsigned long __cpuinit calibrate_delay_direct(void) {return 0;} */ #define LPS_PREC 8 -void __cpuinit calibrate_delay(void) +static unsigned long __cpuinit calibrate_delay_estimate(void) { unsigned long ticks, loopbit; int lps_precision = LPS_PREC; + int loops_per_jiffy; + + loops_per_jiffy = (1<<12); + + while ((loops_per_jiffy <<= 1) != 0) { + /* wait for "start of" clock tick */ + ticks = jiffies; + while (ticks == jiffies) + /* nothing */; + /* Go .. */ + ticks = jiffies; + __delay(loops_per_jiffy); + ticks = jiffies - ticks; + if (ticks) + break; + } + + /* + * Do a binary approximation to get loops_per_jiffy set to + * equal one clock (up to lps_precision bits) + */ + loops_per_jiffy >>= 1; + loopbit = loops_per_jiffy; + while (lps_precision-- && (loopbit >>= 1)) { + loops_per_jiffy |= loopbit; + ticks = jiffies; + while (ticks == jiffies) + /* nothing */; + ticks = jiffies; + __delay(loops_per_jiffy); + if (jiffies != ticks) /* longer than 1 tick */ + loops_per_jiffy &= ~loopbit; + } + return loops_per_jiffy; +} +#define NRETRIES 3 + +void __cpuinit calibrate_delay(void) +{ if (preset_lpj) { loops_per_jiffy = preset_lpj; printk(KERN_INFO @@ -141,38 +180,17 @@ void __cpuinit calibrate_delay(void) printk(KERN_INFO "Calibrating delay using timer specific routine.. "); } else { - loops_per_jiffy = (1<<12); + int i; + unsigned long result; printk(KERN_INFO "Calibrating delay loop... "); - while ((loops_per_jiffy <<= 1) != 0) { - /* wait for "start of" clock tick */ - ticks = jiffies; - while (ticks == jiffies) - /* nothing */; - /* Go .. */ - ticks = jiffies; - __delay(loops_per_jiffy); - ticks = jiffies - ticks; - if (ticks) - break; - } - - /* - * Do a binary approximation to get loops_per_jiffy set to - * equal one clock (up to lps_precision bits) - */ - loops_per_jiffy >>= 1; - loopbit = loops_per_jiffy; - while (lps_precision-- && (loopbit >>= 1)) { - loops_per_jiffy |= loopbit; - ticks = jiffies; - while (ticks == jiffies) - /* nothing */; - ticks = jiffies; - __delay(loops_per_jiffy); - if (jiffies != ticks) /* longer than 1 tick */ - loops_per_jiffy &= ~loopbit; + loops_per_jiffy = 0; + for (i = 0; i < NRETRIES; i++) { + result = calibrate_delay_estimate(); + if (result > loops_per_jiffy) + loops_per_jiffy = result; } + } printk(KERN_CONT "%lu.%02lu BogoMIPS (lpj=%lu)\n", loops_per_jiffy/(500000/HZ), -- cgit v1.2.3 From 723bd9a23048317687b7e6d76ec223f6f8457c85 Mon Sep 17 00:00:00 2001 From: Zheng Da Date: Mon, 12 Jul 2010 22:50:57 +0200 Subject: not export the symbol loops_per_jiffy. --- libdde_linux26/lib/src/init/calibrate.c | 1 - 1 file changed, 1 deletion(-) (limited to 'libdde_linux26/lib/src/init') diff --git a/libdde_linux26/lib/src/init/calibrate.c b/libdde_linux26/lib/src/init/calibrate.c index 687da473..ceb6c5e8 100644 --- a/libdde_linux26/lib/src/init/calibrate.c +++ b/libdde_linux26/lib/src/init/calibrate.c @@ -12,7 +12,6 @@ #include unsigned long loops_per_jiffy = (1<<12); -EXPORT_SYMBOL(loops_per_jiffy); unsigned long lpj_fine; unsigned long preset_lpj; -- cgit v1.2.3 From bb9fd2bd8ff770a003daaf14b8336da490fb19ed Mon Sep 17 00:00:00 2001 From: Zheng Da Date: Mon, 12 Jul 2010 22:52:36 +0200 Subject: use TSC to implement delay. --- libdde_linux26/lib/src/init/calibrate.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'libdde_linux26/lib/src/init') diff --git a/libdde_linux26/lib/src/init/calibrate.c b/libdde_linux26/lib/src/init/calibrate.c index ceb6c5e8..36747582 100644 --- a/libdde_linux26/lib/src/init/calibrate.c +++ b/libdde_linux26/lib/src/init/calibrate.c @@ -43,6 +43,11 @@ static unsigned long __cpuinit calibrate_delay_direct(void) unsigned long good_timer_count = 0; int i; + /* TODO It's not a very good place to call this function + * as TSC is very platform-dependant but calibrate_delay_direct + * isn't that much. */ + use_tsc_delay (); + if (read_current_timer(&pre_start) < 0 ) return 0; -- cgit v1.2.3