Re: [PATCH 01/48] clk: at91: replace usleep() by udelay() calls

[Arnd Bergmann]

On Monday, June 13, 2016 5:24:09 PM CEST Alexandre Belloni wrote:
> On 11/06/2016 at 00:30:36 +0200, Arnd Bergmann wrote :
> > On Saturday, June 11, 2016 12:03:04 AM CEST Alexandre Belloni wrote:
> > > From: Cyrille Pitchen <cyrille.pitchen@xxxxxxxxx>
> > > 
> > > Fix the main and slow clock .prepare() implementations which used to call
> > > usleep() when the scheduler wasn't ready yet.
> > > 
> > 
> > Does this have to be called that early? It seems wasteful to always
> > call udelay() here, when these are functions that are normally
> > allowed to sleep.
> > 
> 
> So I've tested it and something like that would work:
> 
>         if (system_state < SYSTEM_RUNNING)
>                 udelay(osc->startup_usec);
>         else
>                 usleep_range(osc->startup_usec, osc->startup_usec + 1);

I think that's reasonable in this case.

> But I'm afraid it would be the first driver to actually do something
> like that (however, it is already the only driver trying to sleep). 

We have a lot of drivers that call potentially sleeping function from
the .prepare callback, e.g. when they go to an i2c controller.

	Arnd