[PATCH v5 07/15] ARM: mxs: Add gpio support

[Uwe Kleine-König]

Hi Shawn,

On Mon, Dec 13, 2010 at 04:19:41PM +0800, Shawn Guo wrote:
> On Mon, Dec 13, 2010 at 01:10:22AM -0700, Guo Shawn-R65073 wrote:
> > On Mon, Dec 13, 2010 at 12:57:38AM -0700, Uwe Kleine-König wrote:
> > > On Mon, Dec 13, 2010 at 03:28:14PM +0800, Shawn Guo wrote:
> > > > On Fri, Dec 10, 2010 at 03:24:16AM -0700, Uwe Kleine-König wrote:
> > > > > On Fri, Dec 10, 2010 at 04:06:40PM +0800, Shawn Guo wrote:
> > > > > > +		__raw_writel(~0, port[i].base +
> > > > > > +				PINCTRL_IRQSTAT(i) + MXS_CLR_ADDR);
> > > > > Why not __raw_writel(0, port[i].base + PINCTRL_IRQSTAT(i)) ?
> > > > > (And note that applying ~ on a signed integer isn't portable in
> > > > > general.  For all sane archs this is the same as ~0U though and ARM is
> > > > > sane (here), still I think it's good to be aware of such things and
> > > > > avoid them if easily possible.)
> > > > > 
> > > > The i.MX28 RM section 9.4.78 tells "Software may clear any bit in this
> > > > register by writing a 1 to the bit at the SCT clear address".
> > > I didn't say that __raw_writel(~0,  ... + MXS_CLR_ADDR) didn't work.
> > > It's just that I consider writing a 0 directly into the PINCTRL_IRQSTAT
> > > register a bit more clear.
> > >  
> > I thought software has to clear bit by writing clear address for this
> > register. Just confirmed with designer it's not necessary, writing 0
> > to register has the same effect as writing 1 to clear address.
> > 
> > So Uwe, Lothar, your suggestion is being taken.  Thanks.
> > 
> I have to say sorry, as the designer just said the same word to me.
> He took it for granted that writing 0 to the address can also clear
> the status. But after checking the RTL code, he told me that
> only writing clear address will work.
Then add a comment and use ~0U please.  And IMHO the reference manual
needs such a comment, too.

Uwe

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