On Tue, Apr 19, 2005 at 06:41:00PM -0700, john stultz wrote:
> Andrew, All,
> Currently the x86-64 HPET code assumes the entire HPET implementation
> from the spec is present. This breaks on boxes that do not implement the
> optional legacy timer replacement functionality portion of the spec.
>
> This patch fixes this issue, allowing x86-64 systems that cannot use the
> HPET for the timer interrupt and RTC to still use the HPET as a time
> source. I've tested this patch on a system systems without HPET, with
> HPET but without legacy timer replacement, as well as HPET with legacy
> timer replacement.
>
> I'm currently working on a similar patch for i386.
You should it get reviewed by Vojtech who wrote the original x86-64 HPET
code.
-Andi
>
> Please consider for your tree.
>
> thanks
> -john
>
> Changelog:
> A0: First sent to lkml
> A1: Implemented suggestions from Venkatesh
> A2: Whitespace cleanup.
>
> linux-2.6.12-rc2_hpet-nolegacy-fix_A2.patch
> ===========================================
> diff -Nru a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
> --- a/arch/x86_64/kernel/time.c 2005-04-19 18:28:49 -07:00
> +++ b/arch/x86_64/kernel/time.c 2005-04-19 18:28:49 -07:00
> @@ -60,6 +60,7 @@
> unsigned int cpu_khz; /* TSC clocks /
> usec, not used here */
> static unsigned long hpet_period; /* fsecs / HPET clock */
> unsigned long hpet_tick; /* HPET clocks /
> interrupt */
> +static int hpet_use_timer;
> unsigned long vxtime_hz = PIT_TICK_RATE;
> int report_lost_ticks; /* command line option
> */
> unsigned long long monotonic_base;
> @@ -297,7 +298,7 @@
>
> last_offset = vxtime.last;
> base = monotonic_base;
> - this_offset = hpet_readl(HPET_T0_CMP) - hpet_tick;
> + this_offset = hpet_readl(HPET_COUNTER);
>
> } while (read_seqretry(&xtime_lock, seq));
> offset = (this_offset - last_offset);
> @@ -373,7 +374,14 @@
>
> write_seqlock(&xtime_lock);
>
> - if (vxtime.hpet_address) {
> + if (vxtime.hpet_address)
> + offset = hpet_readl(HPET_COUNTER);
> +
> + if (hpet_use_timer) {
> + /* if we're using the hpet timer functionality,
> + * we can more accurately know the counter value
> + * when the timer interrupt occured.
> + */
> offset = hpet_readl(HPET_T0_CMP) - hpet_tick;
> delay = hpet_readl(HPET_COUNTER) - offset;
> } else {
> @@ -794,17 +802,18 @@
> * Set up timer 0, as periodic with first interrupt to happen at hpet_tick,
> * and period also hpet_tick.
> */
> -
> - hpet_writel(HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL |
> + if (hpet_use_timer) {
> + hpet_writel(HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL |
> HPET_TN_32BIT, HPET_T0_CFG);
> - hpet_writel(hpet_tick, HPET_T0_CMP);
> - hpet_writel(hpet_tick, HPET_T0_CMP); /* AK: why twice? */
> -
> + hpet_writel(hpet_tick, HPET_T0_CMP);
> + hpet_writel(hpet_tick, HPET_T0_CMP); /* AK: why twice? */
> + cfg |= HPET_CFG_LEGACY;
> + }
> /*
> * Go!
> */
>
> - cfg |= HPET_CFG_ENABLE | HPET_CFG_LEGACY;
> + cfg |= HPET_CFG_ENABLE;
> hpet_writel(cfg, HPET_CFG);
>
> return 0;
> @@ -825,8 +834,7 @@
>
> id = hpet_readl(HPET_ID);
>
> - if (!(id & HPET_ID_VENDOR) || !(id & HPET_ID_NUMBER) ||
> - !(id & HPET_ID_LEGSUP))
> + if (!(id & HPET_ID_VENDOR) || !(id & HPET_ID_NUMBER))
> return -1;
>
> hpet_period = hpet_readl(HPET_PERIOD);
> @@ -836,6 +844,8 @@
> hpet_tick = (1000000000L * (USEC_PER_SEC / HZ) + hpet_period / 2) /
> hpet_period;
>
> + hpet_use_timer = (id & HPET_ID_LEGSUP);
> +
> return hpet_timer_stop_set_go(hpet_tick);
> }
>
> @@ -892,9 +902,11 @@
> set_normalized_timespec(&wall_to_monotonic,
> -xtime.tv_sec, -xtime.tv_nsec);
>
> - if (!hpet_init()) {
> + if (!hpet_init())
> vxtime_hz = (1000000000000000L + hpet_period / 2) /
> hpet_period;
> +
> + if (hpet_use_timer) {
> cpu_khz = hpet_calibrate_tsc();
> timename = "HPET";
> } else {
> @@ -940,12 +952,12 @@
> if (oem_force_hpet_timer())
> notsc = 1;
> if (vxtime.hpet_address && notsc) {
> - timetype = "HPET";
> + timetype = hpet_use_timer ? "HPET" : "PIT/HPET";
> vxtime.last = hpet_readl(HPET_T0_CMP) - hpet_tick;
> vxtime.mode = VXTIME_HPET;
> do_gettimeoffset = do_gettimeoffset_hpet;
> } else {
> - timetype = vxtime.hpet_address ? "HPET/TSC" : "PIT/TSC";
> + timetype = hpet_use_timer ? "HPET/TSC" : "PIT/TSC";
> vxtime.mode = VXTIME_TSC;
> }
>
>
>
-
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