diff options
| -rw-r--r-- | init/calibrate.c | 73 |
1 files changed, 40 insertions, 33 deletions
diff --git a/init/calibrate.c b/init/calibrate.c index 24fe022c55f..b71643a7aca 100644 --- a/init/calibrate.c +++ b/init/calibrate.c @@ -119,10 +119,47 @@ 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_converge(void) { - unsigned long ticks, loopbit; + unsigned long lpj, ticks, loopbit; int lps_precision = LPS_PREC; + + lpj = (1<<12); + while ((lpj <<= 1) != 0) { + /* wait for "start of" clock tick */ + ticks = jiffies; + while (ticks == jiffies) + /* nothing */; + /* Go .. */ + ticks = jiffies; + __delay(lpj); + ticks = jiffies - ticks; + if (ticks) + break; + } + + /* + * Do a binary approximation to get lpj set to + * equal one clock (up to lps_precision bits) + */ + lpj >>= 1; + loopbit = lpj; + while (lps_precision-- && (loopbit >>= 1)) { + lpj |= loopbit; + ticks = jiffies; + while (ticks == jiffies) + /* nothing */; + ticks = jiffies; + __delay(lpj); + if (jiffies != ticks) /* longer than 1 tick */ + lpj &= ~loopbit; + } + + return lpj; +} + +void __cpuinit calibrate_delay(void) +{ static bool printed; if (preset_lpj) { @@ -139,39 +176,9 @@ void __cpuinit calibrate_delay(void) pr_info("Calibrating delay using timer " "specific routine.. "); } else { - loops_per_jiffy = (1<<12); - if (!printed) pr_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 = calibrate_delay_converge(); } if (!printed) pr_cont("%lu.%02lu BogoMIPS (lpj=%lu)\n", |