diff options
Diffstat (limited to 'packages/linux/ixp4xx-kernel/2.6.16/85-timer.patch')
| -rw-r--r-- | packages/linux/ixp4xx-kernel/2.6.16/85-timer.patch | 280 |
1 files changed, 280 insertions, 0 deletions
diff --git a/packages/linux/ixp4xx-kernel/2.6.16/85-timer.patch b/packages/linux/ixp4xx-kernel/2.6.16/85-timer.patch new file mode 100644 index 0000000000..3ee670f1e9 --- /dev/null +++ b/packages/linux/ixp4xx-kernel/2.6.16/85-timer.patch @@ -0,0 +1,280 @@ + arch/arm/mach-ixp4xx/common.c | 165 +++++++++++++++++++++++++++++++++--- + arch/arm/mach-ixp4xx/nslu2-setup.c | 5 + + include/asm-arm/arch-ixp4xx/nslu2.h | 5 - + include/asm-arm/arch-ixp4xx/timex.h | 23 +++-- + 4 files changed, 176 insertions(+), 22 deletions(-) + +--- linux-nslu2.orig/arch/arm/mach-ixp4xx/common.c 2006-02-06 20:37:01.000000000 +0100 ++++ linux-nslu2/arch/arm/mach-ixp4xx/common.c 2006-02-06 22:34:55.000000000 +0100 +@@ -241,36 +241,165 @@ void __init ixp4xx_init_irq(void) + * IXP4xx timer tick + * We use OS timer1 on the CPU for the timer tick and the timestamp + * counter as a source of real clock ticks to account for missed jiffies. ++ * ++ * 'CLOCK_TICK_RATE' is the nominal number of internal ticks per second, ++ * this is significantly greater than the actual number on any ixp4xx ++ * board. Neither this nor 'LATCH' are required by this code because ++ * the only requirement is to generate HZ timer_tick calls per second. + *************************************************************************/ ++#if TICK_NSEC * HZ != 1000000000 ++ /* This will cause the jiffies to drift unnecessarily. */ ++# error CLOCK_TICK_RATE should be a multiple of HZ for this code ++#endif ++ ++/* These are the control registers for the interrupt handler, they must ++ * only be read and written by the interrupt handler and by the init ++ * method (which sets them to 0). ++ */ ++static volatile u32 last_timer_time; ++static volatile int accumulated_error; ++ ++/* Most ixp4xx boards have 66.6666MHz crystals, so default to this, reset ++ * this from the board level code if required. The following variables ++ * must be *written* only by set_board_tick_rate ++ */ ++static u32 board_tick_rate; ++static u32 board_tick_per_1000; /* board_tick_rate/1000 */ ++static u32 timer_count; ++ ++/* The following symbol may be written to change the current tick rate, ++ * it is read by the interrupt handler and used to reload the timer. ++ * The 'real' value (the one in use) is 'board_tick_rate' above. ++ * NOTE: this can be tweaked to match the actual crystal on a particular ++ * machine. ++ */ ++volatile u32 ixp4xx_board_tick_rate = 66666600; ++EXPORT_SYMBOL(ixp4xx_board_tick_rate); ++ ++/* The set API may run asynchronously in the presence of interrupts, ++ * everything it does it is both atomic and complete (notice that it ++ * doesn't change any of the 'volatile' values). The mathematics in ++ * here require the following values. Changing the board tick rate ++ * implies an unknown error in the current timestamp tick count. ++ */ ++#if IXP4XX_OST_RELOAD_MASK != 3 || IXP4XX_OST_ENABLE != 1 ++# error unexpected value for timer reload mask ++#endif ++static void set_board_tick_rate(u32 rate) { ++ u32 reload; ++ ++ /* Store the two effectively informational rate values, the ++ * error calculation is (rate - count*HZ) (above), and rate ++ * is changed first, this can cause a temporary error which ++ * will be corrected on the next interrupt. ++ */ ++ board_tick_rate = rate; ++ board_tick_per_1000 = (rate+500)/1000; ++ ++ /* Calculate the correct value to load into the timer countdown ++ * register, the low two bits must be b01 (to enable the timer). ++ * Select the top bits to be as close to the desired value as ++ * possible. ++ * ++ * First find the best value, regardless of the low two bits - ++ * this is the value used in the interrupt calculation even though ++ * it cannot necessarily be set into the register. ++ */ ++ timer_count = (rate + (HZ/2))/HZ; ++ ++ /* Now the timer_ticks are being generated at this rate, calculate ++ * an appropriate value for the register. This stores a 30 bit ++ * value which gives a period of 4*x+1, we want: ++ * ++ * 4*x+1 = board_tick_rate/HZ ++ * ++ * This needs to be rounded to the closest 4*HZ value: ++ * ++ * x = ((board_tick_rate-HZ) + (4*HZ)/2) / 4*HZ ++ * x = (board_tick_rate+HZ) / (4*HZ); ++ */ ++ reload = (board_tick_rate + HZ) / HZ; ++ reload = (reload & ~IXP4XX_OST_RELOAD_MASK) | IXP4XX_OST_ENABLE; ++ *IXP4XX_OSRT1 = reload; + +-static unsigned volatile last_jiffy_time; ++ /* If the clock is drifing, look in syslog: */ ++ printk(KERN_INFO "IXP4xx: FREQ=%d COUNT=%d\n", rate, reload); ++} + +-#define CLOCK_TICKS_PER_USEC ((CLOCK_TICK_RATE + USEC_PER_SEC/2) / USEC_PER_SEC) ++/* This returns the time in timer ticks since the 'last_timer_time' ++ * recorded above. Use this to avoid arithmetic errors because of ++ * the overflow when the timer wraps. ++ */ ++static inline u32 ixp4xx_timer_delta(void) ++{ ++ return *IXP4XX_OSTS - last_timer_time; ++} + + /* IRQs are disabled before entering here from do_gettimeofday() */ + static unsigned long ixp4xx_gettimeoffset(void) + { +- u32 elapsed; +- +- elapsed = *IXP4XX_OSTS - last_jiffy_time; ++ /* Return the offset of the current time from the last time ++ * timer tick in microseconds. This is only used for the ++ * gettimeofday call. ++ * ++ * The result of this API is at most about 20000 (for a 50Hz ++ * HZ - 20000 uS/tick), the input delta is at most about ++ * 1.3M - 21 bits. ++ */ ++ u32 delta = ixp4xx_timer_delta(); /* About 21 bits max */ ++ /* return delta * 1000000 / board_tick_rate; */ ++ return (delta * 1000 + board_tick_per_1000/2) / board_tick_per_1000; ++} + +- return elapsed / CLOCK_TICKS_PER_USEC; ++/* This is the correct adjustment to the counter to compensate for an ++ * error iff timer_count-1 <= exact_count <= timer_count+1 ++ */ ++static inline int adjustment(int error) { ++ if (error >= HZ) ++ return 1; ++ else if (error <= -HZ) ++ return -1; ++ return 0; + } + + static irqreturn_t ixp4xx_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs) + { ++ u32 rate; ++ u32 count; ++ int error; ++ + write_seqlock(&xtime_lock); + + /* Clear Pending Interrupt by writing '1' to it */ + *IXP4XX_OSST = IXP4XX_OSST_TIMER_1_PEND; + ++ /* If the board tick rate has been changed update the cached ++ * value. ++ */ ++ if (ixp4xx_board_tick_rate != board_tick_rate) { ++ set_board_tick_rate(ixp4xx_board_tick_rate); ++ accumulated_error = 0; ++ } ++ + /* + * Catch up with the real idea of time ++ * ++ * board_tick_rate: actual ixp4xx ticks/second, read-only ++ * accumulated_error: aggregate error/tick * HZ, read/write ++ * timer_count: best ixp4xx ticks per timer_tick, read-only + */ +- while ((*IXP4XX_OSTS - last_jiffy_time) > LATCH) { ++ rate = board_tick_rate; ++ error = accumulated_error; ++ count = timer_count; ++ do { ++ u32 adjusted_count = count + adjustment(error); ++ if (ixp4xx_timer_delta() < adjusted_count) ++ break; + timer_tick(regs); +- last_jiffy_time += LATCH; +- } ++ last_timer_time += adjusted_count; ++ error += rate - adjusted_count*HZ; ++ } while (1); ++ accumulated_error = error; + + write_sequnlock(&xtime_lock); + +@@ -283,17 +412,30 @@ static struct irqaction ixp4xx_timer_irq + .handler = ixp4xx_timer_interrupt, + }; + ++u32 ixp4xx_get_board_tick_rate(void) { ++ return board_tick_rate; ++} ++ ++EXPORT_SYMBOL(ixp4xx_get_board_tick_rate); ++ ++void ixp4xx_set_board_tick_rate(u32 rate) { ++ ixp4xx_board_tick_rate = rate; ++} ++ ++EXPORT_SYMBOL(ixp4xx_set_board_tick_rate); ++ + static void __init ixp4xx_timer_init(void) + { + /* Clear Pending Interrupt by writing '1' to it */ + *IXP4XX_OSST = IXP4XX_OSST_TIMER_1_PEND; + + /* Setup the Timer counter value */ +- *IXP4XX_OSRT1 = (LATCH & ~IXP4XX_OST_RELOAD_MASK) | IXP4XX_OST_ENABLE; ++ set_board_tick_rate(ixp4xx_board_tick_rate); + + /* Reset time-stamp counter */ + *IXP4XX_OSTS = 0; +- last_jiffy_time = 0; ++ last_timer_time = 0; ++ accumulated_error = 0; + + /* Connect the interrupt handler and enable the interrupt */ + setup_irq(IRQ_IXP4XX_TIMER1, &ixp4xx_timer_irq); +@@ -356,4 +498,3 @@ void __init ixp4xx_sys_init(void) + printk("IXP4xx: Using %luMiB expansion bus window size\n", + ixp4xx_exp_bus_size >> 20); + } +- +--- linux-nslu2.orig/arch/arm/mach-ixp4xx/nslu2-setup.c 2006-02-06 22:31:04.000000000 +0100 ++++ linux-nslu2/arch/arm/mach-ixp4xx/nslu2-setup.c 2006-02-06 22:34:55.000000000 +0100 +@@ -119,6 +119,11 @@ static void nslu2_power_off(void) + + static void __init nslu2_init(void) + { ++ /* The NSLU2 has a 33MHz crystal on board - 1.01% different ++ * from the typical value. ++ */ ++ ixp4xx_set_board_tick_rate(66000000); ++ + ixp4xx_sys_init(); + + pm_power_off = nslu2_power_off; +--- linux-nslu2.orig/include/asm-arm/arch-ixp4xx/nslu2.h 2006-02-06 20:37:38.000000000 +0100 ++++ linux-nslu2/include/asm-arm/arch-ixp4xx/nslu2.h 2006-02-06 22:34:55.000000000 +0100 +@@ -35,11 +35,6 @@ + #define NSLU2_PCI_INTD_PIN 8 + + +-/* NSLU2 Timer */ +-#define NSLU2_FREQ 66000000 +-#define NSLU2_CLOCK_TICK_RATE (((NSLU2_FREQ / HZ & ~IXP4XX_OST_RELOAD_MASK) + 1) * HZ) +-#define NSLU2_CLOCK_TICKS_PER_USEC ((NSLU2_CLOCK_TICK_RATE + USEC_PER_SEC/2) / USEC_PER_SEC) +- + /* GPIO */ + + #define NSLU2_GPIO0 0 +--- linux-nslu2.orig/include/asm-arm/arch-ixp4xx/timex.h 2006-01-25 19:12:27.000000000 +0100 ++++ linux-nslu2/include/asm-arm/arch-ixp4xx/timex.h 2006-02-06 22:34:55.000000000 +0100 +@@ -6,10 +6,23 @@ + #include <asm/hardware.h> + + /* +- * We use IXP425 General purpose timer for our timer needs, it runs at +- * 66.66... MHz. We do a convulted calculation of CLOCK_TICK_RATE b/c the +- * timer register ignores the bottom 2 bits of the LATCH value. ++ * In linux/timex.h 'LATCH' is defined as CLOCK_TICK_RATE/HZ and ++ * is the number of internal counts per timer interrupt. Thus ++ * CLOCK_TICK_RATE is LATCH*HZ. ++ * ++ * The actual values of these numbers do not matter, because they ++ * are only used to calculate ACTHZ (rate/latch as a 24.8 fixed ++ * point number), so the value here gives a LATCH of 1 and pretty ++ * much guarantees to flush out any off-by-one errors. ++ * ++ * ACTHZ is equal to HZ, because CLOCK_TICK_RATE is a multiple of ++ * HZ, this is checked in the ixp4xx/common.c code. + */ +-#define FREQ 66666666 +-#define CLOCK_TICK_RATE (((FREQ / HZ & ~IXP4XX_OST_RELOAD_MASK) + 1) * HZ) ++#define CLOCK_TICK_RATE HZ + ++/* The following allow the exact board tick rate to be set and ++ * discovered. The value should be exactly twice the frequency ++ * (in Hz) of the onboard crystal. ++ */ ++extern u32 ixp4xx_get_board_tick_rate(void); ++extern void ixp4xx_set_board_tick_rate(u32 new_rate); |