i386 HPET code

From: john stultz (johnstul_at_us.ibm.com)
Date: 02/03/05

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    To: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Date:	Wed, 02 Feb 2005 18:05:05 -0800

    Hey Venkatesh,
            I've been looking into a bug where i386 2.6 kernels do not boot on IBM
    e325s if HPET_TIMER is enabled (hpet=disable works around the issue).
    When running x86-64 kernels, the issue isn't seen. It appears that after
    the hpet is enabled, we stop receiving timer ticks. I've not played on
    any other HPET enabled systems, nor have I looked at the HPET spec, so
    I'm not sure if this is a hardware issue or not.

    The following patch, which uses the x86-64 code for
    hpet_timer_stop_set_go() seems to fix the issue.

    Your thoughts?

    thanks
    -john

    ===== arch/i386/kernel/time_hpet.c 1.10 vs edited =====
    --- 1.10/arch/i386/kernel/time_hpet.c 2004-11-02 06:40:42 -08:00
    +++ edited/arch/i386/kernel/time_hpet.c 2005-02-02 17:59:27 -08:00
    @@ -64,29 +64,30 @@
     {
             unsigned int cfg;
     
    - /*
    - * Stop the timers and reset the main counter.
    - */
    +/*
    + * Stop the timers and reset the main counter.
    + */
    +
             cfg = hpet_readl(HPET_CFG);
    - cfg &= ~HPET_CFG_ENABLE;
    + cfg &= ~(HPET_CFG_ENABLE | HPET_CFG_LEGACY);
             hpet_writel(cfg, HPET_CFG);
             hpet_writel(0, HPET_COUNTER);
             hpet_writel(0, HPET_COUNTER + 4);
     
    - /*
    - * Set up timer 0, as periodic with first interrupt to happen at
    - * hpet_tick, and period also hpet_tick.
    - */
    - cfg = hpet_readl(HPET_T0_CFG);
    - cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC |
    - HPET_TN_SETVAL | HPET_TN_32BIT;
    - hpet_writel(cfg, HPET_T0_CFG);
    - hpet_writel(tick, HPET_T0_CMP);
    +/*
    + * 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 |
    + HPET_TN_32BIT, HPET_T0_CFG);
    + hpet_writel(hpet_tick, HPET_T0_CMP);
    + hpet_writel(hpet_tick, HPET_T0_CMP); /* AK: why twice? */
    +
    +/*
    + * Go!
    + */
     
    - /*
    - * Go!
    - */
    - cfg = hpet_readl(HPET_CFG);
             cfg |= HPET_CFG_ENABLE | HPET_CFG_LEGACY;
             hpet_writel(cfg, HPET_CFG);
     

    -
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