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From: andrew@lunn.ch (Andrew Lunn)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/5] clk: mvebu: Add core-divider clock
Date: Thu, 26 Sep 2013 17:56:56 +0200	[thread overview]
Message-ID: <20130926155656.GF18244@lunn.ch> (raw)
In-Reply-To: <20130926151240.GB4583@localhost>

> > > +	/* Valid ratio are 1:4, 1:5, 1:6 and 1:8 */
> > > +	u32 div;
> > > +
> > > +	div = *parent_rate / rate;
> > > +	if (div <= 4)
> > > +	   div = 4;
> > > +	   else if (div <= 5)
> > > +	   	div = 5;
> > > +		else if (div <= 6)
> > > +		     div = 6;
> > > +		     else
> > > +			div = 8;
> > > +
> > > +	return *parent_rate / div;
> > > +}
> > 
> > This looks odd. Is not the following clearer?
> > 
> > 	div = *parent_rate / rate;
> > 	if (div < 5)
> > 	   div = 4;
> > 	   else if (div > 6)
> > 		div = 8;
> > 
> 
> Mmmm... no, it's not at all clearer to me.
> IMHO, the original construction explicitly show the possible ratios:
> 
> 	/* If it's smaller than or equal to 4, set to 4 */
> 	if (div <= 4)
> 		div = 4;
> 
> 	/* Otherwise, if it's between 4 and 5, set to 5 */
> 	else if (div <= 5)
> 	 	div = 5;

If div was a float or double, i would probably agree. But its a u32.
It cannot be between 4 and 5. It must be 5. So it becomes

 	if (div <= 4)
 		div = 4;
        else if (div == 5)
	        div = 5;
        else if (div == 6)
                div = 6
        else 
	    div = 8

Those two middle statements look odd to me...

      Andrew

WARNING: multiple messages have this Message-ID (diff)
From: Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>
To: Ezequiel Garcia
	<ezequiel.garcia-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
Cc: Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>,
	linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	Jason Cooper <jason-NLaQJdtUoK4Be96aLqz0jA@public.gmane.org>,
	Mike Turquette
	<mturquette-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
	Emilio Lopez <elopez93-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Gregory Clement
	<gregory.clement-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>,
	Lior Amsalem <alior-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
	Thomas Petazzoni
	<thomas.petazzoni-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>,
	Tawfik Bayouk <tawfik-eYqpPyKDWXRBDgjK7y7TUQ@public.gmane.org>,
	devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH 1/5] clk: mvebu: Add core-divider clock
Date: Thu, 26 Sep 2013 17:56:56 +0200	[thread overview]
Message-ID: <20130926155656.GF18244@lunn.ch> (raw)
In-Reply-To: <20130926151240.GB4583@localhost>

> > > +	/* Valid ratio are 1:4, 1:5, 1:6 and 1:8 */
> > > +	u32 div;
> > > +
> > > +	div = *parent_rate / rate;
> > > +	if (div <= 4)
> > > +	   div = 4;
> > > +	   else if (div <= 5)
> > > +	   	div = 5;
> > > +		else if (div <= 6)
> > > +		     div = 6;
> > > +		     else
> > > +			div = 8;
> > > +
> > > +	return *parent_rate / div;
> > > +}
> > 
> > This looks odd. Is not the following clearer?
> > 
> > 	div = *parent_rate / rate;
> > 	if (div < 5)
> > 	   div = 4;
> > 	   else if (div > 6)
> > 		div = 8;
> > 
> 
> Mmmm... no, it's not at all clearer to me.
> IMHO, the original construction explicitly show the possible ratios:
> 
> 	/* If it's smaller than or equal to 4, set to 4 */
> 	if (div <= 4)
> 		div = 4;
> 
> 	/* Otherwise, if it's between 4 and 5, set to 5 */
> 	else if (div <= 5)
> 	 	div = 5;

If div was a float or double, i would probably agree. But its a u32.
It cannot be between 4 and 5. It must be 5. So it becomes

 	if (div <= 4)
 		div = 4;
        else if (div == 5)
	        div = 5;
        else if (div == 6)
                div = 6
        else 
	    div = 8

Those two middle statements look odd to me...

      Andrew
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  reply	other threads:[~2013-09-26 15:56 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-09-25 21:28 [PATCH 0/5] Add Core Divider clock support for Armada 370/XP Ezequiel Garcia
2013-09-25 21:28 ` Ezequiel Garcia
2013-09-25 21:28 ` [PATCH 1/5] clk: mvebu: Add core-divider clock Ezequiel Garcia
2013-09-25 21:28 ` [PATCH 2/5] ARM: mvebu: Add Core Divider clock device-tree binding Ezequiel Garcia
2013-09-25 21:28   ` Ezequiel Garcia
2013-09-25 21:28 ` [PATCH 3/5] ARM: mvebu: Add a 2 GHz fixed-clock Armada 370/XP Ezequiel Garcia
2013-09-25 21:28 ` [PATCH 4/5] ARM: mvebu: Add the core-divider clock to " Ezequiel Garcia
2013-09-25 21:28 ` [PATCH 5/5] ARM: mvebu: Add NAND " Ezequiel Garcia
2013-09-25 21:37 ` [PATCH 0/5] Add Core Divider clock support for " Ezequiel Garcia
2013-09-25 21:37   ` Ezequiel Garcia
2013-09-26  7:38   ` Gregory CLEMENT
2013-09-26  7:38     ` Gregory CLEMENT
2013-09-26 15:26     ` Ezequiel Garcia
2013-09-26 15:26       ` Ezequiel Garcia
2013-09-26 15:47       ` Thomas Petazzoni
2013-09-26 15:47         ` Thomas Petazzoni
2013-09-26 16:00         ` Ezequiel Garcia
2013-09-26 16:00           ` Ezequiel Garcia
2013-09-26 16:12           ` Thomas Petazzoni
2013-09-26 16:12             ` Thomas Petazzoni
2013-09-26  8:24   ` [PATCH 1/5] clk: mvebu: Add core-divider clock Andrew Lunn
2013-09-26  8:24     ` Andrew Lunn
2013-09-26 15:12     ` Ezequiel Garcia
2013-09-26 15:12       ` Ezequiel Garcia
2013-09-26 15:56       ` Andrew Lunn [this message]
2013-09-26 15:56         ` Andrew Lunn
2013-09-26 16:55       ` Ben Dooks
2013-09-26 18:29     ` Ezequiel Garcia
2013-09-26 18:29       ` Ezequiel Garcia
2013-09-26  8:36   ` [PATCH 2/5] ARM: mvebu: Add Core Divider clock device-tree binding Andrew Lunn
2013-09-26  8:36     ` Andrew Lunn
2013-09-26 15:04     ` Ezequiel Garcia
2013-09-26 15:04       ` Ezequiel Garcia

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