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

[Lothar Waßmann]

Hi,

Shawn Guo writes:
> Hi Uwe,
> 
> On Fri, Dec 10, 2010 at 03:24:16AM -0700, Uwe Kleine-König wrote:
> > Hello Shawn,
> > 
> > On Fri, Dec 10, 2010 at 04:06:40PM +0800, Shawn Guo wrote:
> [...]
> > > +int __init mxs_gpio_init(struct mxs_gpio_port *port, int cnt)
> > > +{
> > > +	int i, j;
> > > +
> > > +	/* save for local usage */
> > > +	mxs_gpio_ports = port;
> > > +	gpio_table_size = cnt;
> > > +
> > > +	pr_info("MXS GPIO hardware\n");
> > > +
> > > +	for (i = 0; i < cnt; i++) {
> > > +		/* disable the interrupt and clear the status */
> > > +		__raw_writel(0, port[i].base +
> > > +				PINCTRL_PIN2IRQ(i));
> > > +		__raw_writel(0, port[i].base +
> > > +				PINCTRL_IRQEN(i));
> > > +		__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".
> 
> What about writing 0xffffffff into clear address?
> 
When initializing a register it's much more straightforward to write a
zero into the register than to (ab)use the bitwise clear function.


Lothar Waßmann
-- 
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