Re: [PATCH] usb: dwc3: keystone: switch to use runtime pm

[Felipe Balbi]

On Fri, Jan 31, 2014 at 04:13:19PM -0500, Alan Stern wrote:
> On Fri, 31 Jan 2014, Felipe Balbi wrote:
> 
> > probe()
> > {
> > 	...
> > 
> > 	clk_get(dev, "fck");
> > 	clk_prepare(clk);
> > 	clk_enable(clk);
> > 	pm_runtime_set_active(dev);
> > 	pm_runtime_enable(dev);
> > 	pm_runtime_get_sync(dev);
> > 	...
> > }
> 
> > note that because of pm_runtime_set_active() that first
> > pm_runtime_get_sync() in probe() will simply increase the reference
> > counter without calling my ->runtime_resume() callback, which is exactly
> > what we want, as that would completely avoid situations of bad context
> > being restored because of that initial pm_runtime_get_sync().
> 
> Very minor note...  A slightly better way to do the same thing is:
> 
> 	pm_runtime_set_active(dev);
> 	pm_runtime_get_noresume(dev);
> 	pm_runtime_enable(dev);
> 
> The get_noresume says that you want to increment the usage counter
> without performing any callbacks, and doing it before the
> pm_runtime_enable avoids any window during which a runtime suspend
> might somehow occur.

aha, that's perfect :-) Thanks Alan.

-- 
balbi

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