[PATCH 01/11] usb: chipidea: Add power management support

[Peter Chen]

On Mon, Oct 14, 2013 at 10:42:16AM +0200, Sascha Hauer wrote:
> On Mon, Oct 14, 2013 at 03:55:48PM +0800, Peter Chen wrote:
> > On Mon, Oct 14, 2013 at 10:04:58AM +0200, Lothar Waßmann wrote:
> > > Hi,
> > > 
> > > Peter Chen wrote:
> > > > This commit adds runtime and system power management support for
> > > > chipidea core. The runtime pm support is controlled by glue
> > > > layer, it can be enabled by flag CI_HDRC_SUPPORTS_RUNTIME_PM.
> > > > 
> > > [...]
> > > > +#ifdef CONFIG_PM
> > > > +static int ci_controller_suspend(struct device *dev)
> > > > +{
> > > > +	struct ci_hdrc *ci = dev_get_drvdata(dev);
> > > > +
> > > > +	dev_dbg(dev, "at %s\n", __func__);
> > > > +
> > > > +	if (atomic_read(&ci->in_lpm))
> > > > +		return 0;
> > > > +
> > > What does this 'atomic_read()' buy you over just testing/assinging a
> > > simple integer. Note that just because the function has 'atomic' in
> > > its name the sequence:
> > > 	atomic_read();
> > > ...
> > > 	atomic_set();
> > > does not magically become an atomic operation.
> > 
> > I just want the read and set are atomic, not the operations
> > between atomic_read and atomic_set.
> 
> It makes no sense to use atomic operations here. atomic types are to
> atomically read/modify/write variables. If all you ever do is
> atomic_read and atomic_set then you can use a simple bool variable.
> 

It is for ARM, but for other platforms, it may not.

-- 

Best Regards,
Peter Chen