linux-kernel - Re: [PATCH v5 1/8] clk: divider: switch to GENMASK()

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Date:	Wed, 22 Jul 2015 16:03:25 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	linux-kernel@...r.kernel.org, Sascha Hauer <kernel@...gutronix.de>,
	Peter De Schrijver <pdeschrijver@...dia.com>,
	Tero Kristo <t-kristo@...com>,
	Russell King <linux@....linux.org.uk>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>
Subject: Re: [PATCH v5 1/8] clk: divider: switch to GENMASK()

On Tue, 2015-07-21 at 16:48 -0700, Stephen Boyd wrote:
> On 07/13, Andy Shevchenko wrote:
> > Convert the code to use GENMASK() helper instead of div_mask() 
> > macro.
> > 
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > ---
> >  drivers/clk/clk-divider.c | 18 ++++++++----------
> >  1 file changed, 8 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c
> > index 706b578..3bde790 100644
> > --- a/drivers/clk/clk-divider.c
> > +++ b/drivers/clk/clk-divider.c
> > @@ -30,8 +30,6 @@
> >  
> 
> #include <linux/bitops.h> ?

In clk-provider.h? It already is using BIT() macro. That's why I didn't
add the header inclusion.

> 
> > @@ -391,10 +389,10 @@ static int clk_divider_set_rate(struct clk_hw 
> > *hw, unsigned long rate,
> >  		spin_lock_irqsave(divider->lock, flags);
> >  
> >  	if (divider->flags & CLK_DIVIDER_HIWORD_MASK) {
> > -		val = div_mask(divider->width) << (divider->shift 
> > + 16);
> > +		val = GENMASK(divider->width - 1, 0) << (divider
> > ->shift + 16);
> >  	} else {
> >  		val = clk_readl(divider->reg);
> > -		val &= ~(div_mask(divider->width) << divider
> > ->shift);
> > +		val &= ~(GENMASK(divider->width - 1, 0) << divider
> > ->shift);
> 
> Shouldn't this be doing the shift in the GENMASK?

It shouldn't. I checked an assembly and it's far complex from the
proposed form.

> 
> 	start = divider->width - 1 + divider->shift;
> 	end = divider->shift;
> 
> 	...
> 
> 		val &= ~GENMASK(start, end);
> 

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy
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