[PATCH v5 1/3] ARM: Introduce atomic MMIO modify

[Will Deacon]

On Wed, Dec 11, 2013 at 08:49:43PM +0000, Ezequiel Garcia wrote:
> On Tue, Dec 10, 2013 at 05:00:25PM +0000, Russell King - ARM Linux wrote:
> > On Tue, Dec 10, 2013 at 04:49:07PM +0000, Mark Brown wrote:
> > > On Tue, Dec 10, 2013 at 11:41:35AM -0300, Ezequiel Garcia wrote:
> > > 
> > > > +void atomic_io_modify_relaxed(void __iomem *reg, u32 mask, u32 set)
> > > > +{
> > > > +	unsigned long flags;
> > > > +	u32 value;
> > > > +
> > > > +	raw_spin_lock_irqsave(&__io_lock, flags);
> > > > +	value = readl_relaxed(reg) & ~mask;
> > > > +	value |= (set & mask);
> > > > +	writel_relaxed(value, reg);
> > > > +	raw_spin_unlock_irqrestore(&__io_lock, flags);
> > > > +}
> > > > +EXPORT_SYMBOL(atomic_io_modify_relaxed);
> > > 
> > > This looks quite generic - why is it in architecture specific code?
> > 
> > because the _relaxed IO operators don't exist on other architectures, and
> > there's been some discussion around whether they should with no conclusions
> > being reached.
> 
> Exactly.
> 
> Will? Catalin? Any comments on this?

Yes: BenH and I managed to come up with an agreement on the relaxed I/O
accessors during kernel summit which I need to write up and send out again.
This would allow for a generic definition of the accessors, then this could
potentially be done in core code.

That said, I think the code you have will work correctly for ARM.

Will