[RFC PATCH] arm/imx/gpio: add spinlock protection
baruch at tkos.co.il
Tue Jul 6 03:40:43 EDT 2010
On Tue, Jul 06, 2010 at 09:17:02AM +0200, Sascha Hauer wrote:
> On Tue, Jul 06, 2010 at 08:00:34AM +0300, Baruch Siach wrote:
> > On Mon, Jul 05, 2010 at 09:52:18AM +0200, Sascha Hauer wrote:
> > > On Sun, Jul 04, 2010 at 10:15:13AM +0300, Baruch Siach wrote:
> > > > The GPIO and IRQ/GPIO registers need protection from concurrent access for
> > > > operations that are not atomic.
> > >
> > > I don't think we need locking here. mxc_gpio_irq_handler is called with
> > > desc->lock held (from the parent interrupt, not the chained interrupts).
> > > Other functions like enable_irq/disable_irq which result in mask/unmask
> > > operations run with interrupts disabled.
> > What about the .set_type method?
> Is only called with interrupts disabled.
> > > Apart from this other architectures do not use locking here aswell.
> > The Nomadic gpio driver does use a spinlock for mask/unmask operations.
> > What about the _set_gpio_direction, and mxc_gpio_set? These functions may be
> > called from a process context (e.g., via sysfs). A context switch between
> > __raw_readl and __raw_writel will cause corruption.
> The gpio_chip functions are protected by a single spinlock in
gpio_direction_input uses the gpio_lock for its own internal sanity check, and
releases it before calling chip->direction_input. The same goes for
The __gpio_set_value function seems not acquire any lock before calling
> The gpio related registers and the irq related regsiters are
> totally orthogonal, so we need no locking between these registers.
~. .~ Tk Open Systems
- baruch at tkos.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -
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