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

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Date:	Tue, 14 Jun 2016 21:35:17 +0530
From:	Afzal Mohammed <afzal.mohd.ma@...il.com>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	linux-kernel@...r.kernel.org,
	Cyrille Pitchen <cyrille.pitchen@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 01/48] clk: at91: replace usleep() by udelay() calls

Hi,

On Mon, Jun 13, 2016 at 05:24:09PM +0200, Alexandre Belloni wrote:
> On 11/06/2016 at 00:30:36 +0200, Arnd Bergmann wrote :

> > 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). 

tglx has suggested to modify clock core to handle a somewhat similar
kind of scenario (probably should work here too) and avoid driver
changes,

http://lkml.kernel.org/r/alpine.DEB.2.11.1606061448010.28031@nanos

Regards
afzal