diff options
Diffstat (limited to 'packages/linux/linux-2.6.22.6/ts72xx/ep93xx-timer-accuracy.diff')
| -rw-r--r-- | packages/linux/linux-2.6.22.6/ts72xx/ep93xx-timer-accuracy.diff | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/packages/linux/linux-2.6.22.6/ts72xx/ep93xx-timer-accuracy.diff b/packages/linux/linux-2.6.22.6/ts72xx/ep93xx-timer-accuracy.diff new file mode 100644 index 0000000000..8254153b69 --- /dev/null +++ b/packages/linux/linux-2.6.22.6/ts72xx/ep93xx-timer-accuracy.diff @@ -0,0 +1,59 @@ + +The ep93xx has a weird timer tick base (983.04 kHz.) This experimental +patch tries to increase time of day accuracy by keeping the number of +ticks until the next jiffy in a fractional value representation. + +Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org> + +Index: linux-2.6.22/arch/arm/mach-ep93xx/core.c +=================================================================== +--- linux-2.6.22.orig/arch/arm/mach-ep93xx/core.c ++++ linux-2.6.22/arch/arm/mach-ep93xx/core.c +@@ -94,19 +94,32 @@ void __init ep93xx_map_io(void) + * track of lost jiffies. + */ + static unsigned int last_jiffy_time; ++static unsigned int next_jiffy_time; ++static unsigned int accumulator; + +-#define TIMER4_TICKS_PER_JIFFY ((CLOCK_TICK_RATE + (HZ/2)) / HZ) ++#define TIMER4_TICKS_PER_JIFFY (983040 / HZ) ++#define TIMER4_TICKS_MOD_JIFFY (983040 % HZ) ++ ++static int after_eq(unsigned long a, unsigned long b) ++{ ++ return ((signed long)(a - b)) >= 0; ++} + + static int ep93xx_timer_interrupt(int irq, void *dev_id) + { + write_seqlock(&xtime_lock); + + __raw_writel(1, EP93XX_TIMER1_CLEAR); +- while ((signed long) +- (__raw_readl(EP93XX_TIMER4_VALUE_LOW) - last_jiffy_time) +- >= TIMER4_TICKS_PER_JIFFY) { +- last_jiffy_time += TIMER4_TICKS_PER_JIFFY; ++ while (after_eq(__raw_readl(EP93XX_TIMER4_VALUE_LOW), next_jiffy_time)) { + timer_tick(); ++ ++ last_jiffy_time = next_jiffy_time; ++ next_jiffy_time += TIMER4_TICKS_PER_JIFFY; ++ accumulator += TIMER4_TICKS_MOD_JIFFY; ++ if (accumulator >= HZ) { ++ next_jiffy_time++; ++ accumulator -= HZ; ++ } + } + + write_sequnlock(&xtime_lock); +Index: linux-2.6.22/include/asm-arm/arch-ep93xx/timex.h +=================================================================== +--- linux-2.6.22.orig/include/asm-arm/arch-ep93xx/timex.h ++++ linux-2.6.22/include/asm-arm/arch-ep93xx/timex.h +@@ -2,4 +2,4 @@ + * linux/include/asm-arm/arch-ep93xx/timex.h + */ + +-#define CLOCK_TICK_RATE 983040 ++#define CLOCK_TICK_RATE (1000 * HZ) |