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

[Shawn Guo]

On Mon, Dec 13, 2010 at 12:57:38AM -0700, Uwe Kleine-König wrote:
> Hi Shawn,
> 
> 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.

> > What about writing 0xffffffff into clear address?
> If you insist on doing that, at least write ~0U which is more portable.
> 

Regards,
Shawn