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From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <JBeulich@suse.com>,
	xen-devel <xen-devel@lists.xenproject.org>
Cc: Dario Faggioli <dario.faggioli@citrix.com>,
	Joao Martins <joao.m.martins@oracle.com>
Subject: Re: [PATCH 4/8] x86/time: calibrate TSC against platform timer
Date: Mon, 20 Jun 2016 15:20:53 +0100	[thread overview]
Message-ID: <6412dddf-5702-c84f-e922-13f6d1081536@citrix.com> (raw)
In-Reply-To: <576149E202000078000F53A1@prv-mh.provo.novell.com>

On 15/06/16 11:28, Jan Beulich wrote:
> --- a/xen/arch/x86/i8259.c
> +++ b/xen/arch/x86/i8259.c
> @@ -359,12 +359,7 @@ void __init init_IRQ(void)
>  
>      apic_intr_init();
>  
> -    /* Set the clock to HZ Hz */
> -#define CLOCK_TICK_RATE 1193182 /* crystal freq (Hz) */
> -#define LATCH (((CLOCK_TICK_RATE)+(HZ/2))/HZ)
> -    outb_p(0x34, PIT_MODE);        /* binary, mode 2, LSB/MSB, ch 0 */
> -    outb_p(LATCH & 0xff, PIT_CH0); /* LSB */
> -    outb(LATCH >> 8, PIT_CH0);     /* MSB */
> +    preinit_pit();

This highlights the fact that we have two unconditional calls to
preinit_pit() during startup, which is one too many.

init_IRQ() is called rather earlier than early_time_init(), but I can't
spot anything inbetween the two calls which would require the PIT to be
set up.  AFAICT, it is safe to just drop the preinit_pit() call here.

> @@ -340,7 +348,8 @@ static struct platform_timesource __init
>      .frequency = CLOCK_TICK_RATE,
>      .read_counter = read_pit_count,
>      .counter_bits = 32,
> -    .init = init_pit
> +    .init = init_pit,
> +    .resume = resume_pit

Please add a redundant comma at the end, to reduce the next diff to
change this block.

~Andrew

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  reply	other threads:[~2016-06-20 14:20 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-15  9:50 [PATCH 0/8] x86/time: improve cross-CPU clock monotonicity (and more) Jan Beulich
2016-06-15 10:26 ` [PATCH 1/8] " Jan Beulich
2016-06-15 10:32   ` Jan Beulich
2016-06-15 22:51   ` Joao Martins
2016-06-16  8:27     ` Jan Beulich
2016-06-16 20:27       ` Joao Martins
2016-06-17  7:32         ` Jan Beulich
2016-06-21 12:05           ` Joao Martins
2016-06-21 12:28             ` Jan Beulich
2016-06-21 13:57               ` Joao Martins
2016-08-02 19:30   ` Andrew Cooper
2016-06-15 10:26 ` [PATCH 2/8] x86: also generate assembler usable equates for synthesized features Jan Beulich
2016-06-20 12:50   ` Andrew Cooper
2016-06-15 10:27 ` [PATCH 3/8] x86/time: introduce and use rdtsc_ordered() Jan Beulich
2016-06-20 12:59   ` Andrew Cooper
2016-06-20 13:06     ` Jan Beulich
2016-06-20 13:07       ` Andrew Cooper
2016-07-11 11:39     ` Dario Faggioli
2016-06-15 10:28 ` [PATCH 4/8] x86/time: calibrate TSC against platform timer Jan Beulich
2016-06-20 14:20   ` Andrew Cooper [this message]
2016-06-20 15:19     ` Jan Beulich
2016-08-02 19:25       ` Andrew Cooper
2016-08-03  9:32         ` Jan Beulich
2016-06-15 10:28 ` [PATCH 5/8] x86/time: correctly honor late clearing of TSC related feature flags Jan Beulich
2016-06-20 14:32   ` Andrew Cooper
2016-06-20 15:20     ` Jan Beulich
2016-07-04 15:39       ` Andrew Cooper
2016-07-04 15:53         ` Jan Beulich
2016-08-02 19:08           ` Andrew Cooper
2016-08-03  9:43             ` Jan Beulich
2016-08-31 13:42               ` Andrew Cooper
2016-08-31 14:03                 ` Jan Beulich
2016-06-15 10:29 ` [PATCH 6/8] x86/time: support 32-bit wide ACPI PM timer Jan Beulich
2016-07-04 15:40   ` Andrew Cooper
2016-06-15 10:30 ` [PATCH 7/8] x86/time: fold recurring code Jan Beulich
2016-07-04 15:43   ` Andrew Cooper
2016-06-15 10:30 ` [PATCH 8/8] x86/time: group time stamps into a structure Jan Beulich
2016-07-04 15:57   ` Andrew Cooper
2016-07-01  7:44 ` Ping: [PATCH 0/8] x86/time: improve cross-CPU clock monotonicity (and more) Jan Beulich

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