Hi Russell, On Tue, Nov 04, 2014 at 06:12:19PM +0000, Russell King - ARM Linux wrote: > On Tue, Nov 04, 2014 at 12:07:14PM +0800, Chen-Yu Tsai wrote: > > + spin_lock_irqsave(data->lock, flags); > > + > > + reg = readl(data->reg); > > + writel(reg & ~BIT(id), data->reg); > > + > > + spin_unlock_irqrestore(data->lock, flags); > > Don't we have generic support for atomic modification of register > values? Hmm, we have it for ARM only - atomic_io_modify() and > atomic_io_modify_relaxed(). > > I guess we should push for those to become cross-arch if we end up > with generic drivers shared between other architectures.
IIRC, the atomic MMIO accessors are doing exactly that, but with a global lock for all MMIO accesses, while here we protect a single register. I'm not really sure that sharing this spinlock across the whole system is worth it and scales that well. Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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