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

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Message-ID: <20160613152409.GD3240@piout.net>
Date:	Mon, 13 Jun 2016 17:24:09 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	linux-kernel@...r.kernel.org,
	Cyrille Pitchen <cyrille.pitchen@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	linux-clk@...r.kernel.org
Subject: Re: [PATCH 01/48] clk: at91: replace usleep() by udelay() calls

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@...el.com>
> > 
> > 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);

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). 

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com