linux-kernel - Re: [PATCH 2/8] clocksource: sun4i: Add clocksource and sched clock drivers

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Date:	Thu, 27 Jun 2013 19:21:44 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Baruch Siach <baruch@...s.co.il>
Cc:	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Emilio Lopez <emilio@...pez.com.ar>,
	linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com,
	sunny@...winnertech.com, shuge@...winnertech.com,
	kevin@...winnertech.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/8] clocksource: sun4i: Add clocksource and sched clock
 drivers

Hi Baruch,

On Thu, Jun 27, 2013 at 12:46:49PM +0300, Baruch Siach wrote:
> On Thu, Jun 27, 2013 at 11:35:58AM +0200, Maxime Ripard wrote:
> > On Thu, Jun 27, 2013 at 09:02:34AM +0300, Baruch Siach wrote:
> > > On Wed, Jun 26, 2013 at 11:16:55PM +0200, Maxime Ripard wrote:
> > > > +static u32 sun4i_timer_sched_read(void)
> > > 
> > > You commit message mentions "64 bits free running counter", but this one only 
> > > returns 32 bit.
> > 
> > Yeah, the callback setup by setup_sched_clock is supposed to be
> > returning a u32, and clocksource_mmio_init only accepts up to 32 bits as
> > well, so I'm only using the lower 32bits of this 64 bits counter.
> > 
> > I'll amend the commit log to state this.
> 
> But using 64 bit counter for sched_clock is much easier that using 32 bit one. 

Easier in what aspect? Both API looks similar.

> You can either wait for the rest of Stephen's patch set 
> (http://thread.gmane.org/gmane.linux.ports.arm.msm/4092) before adding 64 bit, 
> or you can just make the trivial change to the now generic sched_clock code.

I'll wait for the Stephen's patches to be merged then, and add support
for 64bits counters to clocksource_mmio_init.

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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