linux-kernel - Re: [PATCH v5 21/29] nios2: Time keeping

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Message-ID: <alpine.DEB.2.11.1410281614390.5308@nanos>
Date:	Tue, 28 Oct 2014 16:15:48 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Ley Foon Tan <lftan@...era.com>
cc:	Arnd Bergmann <arnd@...db.de>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Chung-Lin Tang <cltang@...esourcery.com>
Subject: Re: [PATCH v5 21/29] nios2: Time keeping

On Tue, 28 Oct 2014, Ley Foon Tan wrote:
> On Sel, 2014-10-28 at 10:23 +0100, Arnd Bergmann wrote:
> > On Tuesday 28 October 2014 10:46:29 Ley Foon Tan wrote:
> > > On Sun, Oct 26, 2014 at 5:10 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> > > > On Fri, 24 Oct 2014, Ley Foon Tan wrote:
> > > >> +#ifndef _ASM_NIOS2_TIMEX_H
> > > >> +#define _ASM_NIOS2_TIMEX_H
> > > >> +
> > > >> +typedef unsigned long cycles_t;
> > > >> +
> > > >> +extern cycles_t get_cycles(void);
> > > >> +
> > > >> +#define ARCH_HAS_READ_CURRENT_TIMER
> > > >
> > > > Why does NIOS need that? Does it have a hardware implementation
> > > > dependent clock frequency which needs to be calibrated at boot time?
> > > This is suggestion from Arnd to use read_current_timer instead of using
> > > expensive delay loop calibration during boot.
> > 
> > My mistake, sorry. I think the right way is to define
> > calibrate_delay_is_known() rather than read_current_timer(), I was
> > getting confused by the ARM implementation that does both.
> Hi Arnd,
> No problem, I can change that. But, seem that we don't need to have
> calibrate_delay_is_known() as well. We can just set "lpj_fine" variable,
> arm64 uses this.

Please do so and resend the result so I can have another look and add
my reviewed tag then.

Thanks,

	tglx
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