linux-kernel - RE: [PATCH 2/5] Clocksource: Flextimer: Use internal clocksource read API.

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Date:	Thu, 4 Sep 2014 08:43:28 +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>,
	"Dongsheng.Wang@...escale.com" <Dongsheng.Wang@...escale.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2/5] Clocksource: Flextimer: Use internal clocksource read
 API.

> >
> > Since the FTM will be in BE mode on LS1 platform, but will be in LE mode
> > On LS2 platform.
> >
> > And ftm_clocksource_read_up() will adapt to this different.
> 
> You are missing the point. Why do you want a conditional in a hot
> path? You know at init time whether the thing is BE or LE, so you can
> have separate functions for BE/LE or whatever and register that with
> clocksource_mmio_init(). i.e.
> 
>      if (be)
>      	clocksource_mmio_init(....., cs_read_be);
>      else if (le)
>      	clocksource_mmio_init(....., cs_read_le);
>      else if (magic)
>      	clocksource_mmio_init(....., cs_read_magic);
> 

There already has the following access interfaces:

static inline u32 ftm_readl(void __iomem *addr)
{
        if (priv->big_endian)
                return ioread32be(addr);
        else
                return ioread32(addr);
}

static inline void ftm_writel(u32 val, void __iomem *addr)
{
        if (priv->big_endian)
                iowrite32be(val, addr);
        else
                iowrite32(val, addr);
}

So I added the following code:

static cycle_t ftm_clocksource_read_up(struct clocksource *c)
{
        return ftm_readl(priv->clksrc_base + FTM_CNT) & 0xffff;
}

clocksource_mmio_init(.....,ftm_clocksource_read_up);

Is this okay ?

Thanks,

BRs
Xiubo


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