Re: [PATCH] x86/HPET: don't disable interrupt delivery right after setting it up

[Malcolm Crossley <malcolm.crossley@citrix.com>]

On 27/09/12 15:40, Jan Beulich wrote:
> We shouldn't clear HPET_TN_FSB right after we (indirectly, via
> request_irq()) enabled it for the channels we intend to use for
> broadcasts.
>
> This fixes a regression introduced by c/s 25103:0b0e42dc4f0a.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> ---
> This fixes the MWAIT idle driver problem on the box that I was able to
> (artificially) reproduce it with. Hence I subsequently intend to revert
> 25960:6bf8b882df8f, but I'm not intending to do this before getting a
> push there.
>
> I'm surprised that this didn't hit anyone so far with the ACPI-based
> idle driver...
Good catch Jan, Does this fix need backporting to Xen 4.2 and 4.1?
> --- 2012-09-21.orig/xen/arch/x86/hpet.c	2012-09-27 16:10:35.000000000 +0200
> +++ 2012-09-21/xen/arch/x86/hpet.c	2012-09-27 16:10:07.000000000 +0200
> @@ -533,7 +533,7 @@ void __init hpet_broadcast_init(void)
>       {
>           /* set HPET Tn as oneshot */
>           cfg = hpet_read32(HPET_Tn_CFG(hpet_events[i].idx));
> -        cfg &= ~(HPET_TN_LEVEL | HPET_TN_PERIODIC | HPET_TN_FSB);
> +        cfg &= ~(HPET_TN_LEVEL | HPET_TN_PERIODIC);
>           cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
>           hpet_write32(cfg, HPET_Tn_CFG(hpet_events[i].idx));
>   
> @@ -590,7 +590,7 @@ void hpet_broadcast_resume(void)
>   
>           /* set HPET Tn as oneshot */
>           cfg = hpet_read32(HPET_Tn_CFG(hpet_events[i].idx));
> -        cfg &= ~(HPET_TN_LEVEL | HPET_TN_PERIODIC | HPET_TN_FSB);
> +        cfg &= ~(HPET_TN_LEVEL | HPET_TN_PERIODIC);
>           cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
>           hpet_write32(cfg, HPET_Tn_CFG(hpet_events[i].idx));
>   
>