linux-kernel - RE: [PATCH v2] clocksource: Add BE APIs support for clocksource counter reading.

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Date:	Tue, 30 Sep 2014 02:12:37 +0000
From:	"Li.Xiubo@...escale.com" <Li.Xiubo@...escale.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
	"john.stultz@...aro.org" <john.stultz@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] clocksource: Add BE APIs support for clocksource
 counter reading.

Hi,

> Subject: RE: [PATCH v2] clocksource: Add BE APIs support for clocksource
> counter reading.
> 
> On Sun, 28 Sep 2014, Li.Xiubo@...escale.com wrote:
> > > Subject: Re: [PATCH v2] clocksource: Add BE APIs support for clocksource
> > > counter reading.
> > >
> > > On Fri, 26 Sep 2014, Xiubo Li wrote:
> > > > For now I just added  _be() support using ioread{16,32}be.
> > > > And i have a check of the clocksource drivers, didn't find anyone
> > > > using LE mode on one BE SoC, so _le() APIs is not needed.
> > >
> > > Nonsense. The existing clocksource_mmio accessor function are
> > > providing LE access independent of the CPU endianess. So we don't need
> > > an _le() API simply because we have it already.
> > >
> > > >  cycle_t clocksource_mmio_readl_up(struct clocksource *c)
> > > >  {
> > > > -	return (cycle_t)readl_relaxed(to_mmio_clksrc(c)->reg);
> > > > +	return (cycle_t)ioread32(to_mmio_clksrc(c)->reg);
> > >
> > > And how exactly is this change related to adding BE support?
> > >
> >
> > Actually not very much, since the _be() APIs are using ioread{16,32}be(),
> > so I think using ioread{16,32}() will be less odd to having two different
> > accessors here.
> >
> > Wouldn't this be more unified somehow ?
> 
> Changing existing code wants to be a separate patch with a proper
> changelog and a proper argument WHY it needs to be changed in the
> first place.
> 
> So please provide that separate patch first with a VERY REASONABLE
> explanation in the changelog WHY the existing readl_relaxed() should
> be replaced by ioread32().
> 

Okay, I will follow your advice.

Thanks,

BRs
Xiubo




> Thanks,
> 
> 	tglx
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