From: Aubrey Li <aubrey.intel@gmail.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Li, Aubrey" <aubrey.li@linux.intel.com>,
"Lendacky, Thomas" <Thomas.Lendacky@amd.com>,
Daniel Drake <drake@endlessm.com>,
"x86@kernel.org" <x86@kernel.org>,
"H . Peter Anvin" <hpa@zytor.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Endless Linux Upstreaming Team <linux@endlessm.com>,
Jiri Slaby <jslaby@suse.cz>
Subject: Re: [PATCH] x86/apic: Handle missing global clockevent gracefully
Date: Mon, 12 Aug 2019 20:59:42 +0800 [thread overview]
Message-ID: <CAERHkrttXdZhZHZs+JasZU6a2kEb1vc6KB25+LbpQycenJZpOg@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1908121423040.7324@nanos.tec.linutronix.de>
On Mon, Aug 12, 2019 at 8:25 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Mon, 12 Aug 2019, Li, Aubrey wrote:
> > On 2019/8/9 20:54, Thomas Gleixner wrote:
> > > + local_irq_disable();
> > > /*
> > > * Setup the APIC counter to maximum. There is no way the lapic
> > > * can underflow in the 100ms detection time frame
> > > */
> > > __setup_APIC_LVTT(0xffffffff, 0, 0);
> > >
> > > - /* Let the interrupts run */
> > > - local_irq_enable();
> > > + /*
> > > + * Methods to terminate the calibration loop:
> > > + * 1) Global clockevent if available (jiffies)
> > > + * 2) TSC if available and frequency is known
> > > + */
> > > + jif_start = READ_ONCE(jiffies);
> > > +
> > > + if (tsc_khz) {
> > > + tsc_start = rdtsc();
> > > + tsc_perj = div_u64((u64)tsc_khz * 1000, HZ);
> > > + }
> > > +
> > > + while (lapic_cal_loops <= LAPIC_CAL_LOOPS) {
> >
> > Is this loop still meaningful, can we just invoke the handler twice
> > before and after the tick?
>
> And that solves what?
>
I meant, can we do this one time?
- lapic_cal_t1 = read APIC counter
- /* Wait for a tick to elapse */
- lapic_cal_t2 = read APIC counter
I'm not clear why we still need this loop, to use the
existing lapic_cal_handler()?
Thanks,
-Aubrey
next prev parent reply other threads:[~2019-08-12 12:59 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-01 6:24 setup_boot_APIC_clock() NULL dereference during early boot on reduced hardware platforms Daniel Drake
2019-08-01 7:16 ` Aubrey Li
2019-08-01 7:35 ` Thomas Gleixner
2019-08-01 7:56 ` Aubrey Li
2019-08-01 8:13 ` Thomas Gleixner
2019-08-01 8:21 ` Li, Aubrey
2019-08-01 10:13 ` Thomas Gleixner
2019-08-01 15:44 ` Lendacky, Thomas
2019-08-08 20:36 ` Thomas Gleixner
2019-08-08 21:01 ` Lendacky, Thomas
2019-08-08 21:08 ` Thomas Gleixner
2019-08-08 21:36 ` Lendacky, Thomas
2019-08-09 12:54 ` [PATCH] x86/apic: Handle missing global clockevent gracefully Thomas Gleixner
2019-08-09 12:59 ` Jiri Slaby
2019-08-09 13:58 ` Lendacky, Thomas
2019-08-09 19:40 ` Thomas Gleixner
2019-08-12 6:16 ` Daniel Drake
2019-08-12 7:03 ` Jiri Slaby
2019-08-15 5:02 ` Daniel Drake
2019-08-12 7:46 ` Li, Aubrey
2019-08-12 12:24 ` Thomas Gleixner
2019-08-12 12:59 ` Aubrey Li [this message]
2019-08-12 17:11 ` Thomas Gleixner
2019-08-19 10:37 ` [tip:x86/urgent] " tip-bot for Thomas Gleixner
2019-08-01 9:00 ` setup_boot_APIC_clock() NULL dereference during early boot on reduced hardware platforms Daniel Drake
2019-08-01 10:17 ` Thomas Gleixner
2019-08-01 7:27 ` Thomas Gleixner
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