linux-kernel - Re: [PATCH] dmaengine: dw: support for clockless platforms

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Date:	Wed, 11 Feb 2015 12:07:27 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	Viresh Kumar <viresh.kumar@...aro.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Vinod Koul <vinod.koul@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	dmaengine@...r.kernel.org
Subject: Re: [PATCH] dmaengine: dw: support for clockless platforms

On Wed, Feb 11, 2015 at 02:02:39PM +0200, Andy Shevchenko wrote:
> On Wed, 2015-02-11 at 10:10 +0800, Viresh Kumar wrote:
> > >         chip->clk = devm_clk_get(chip->dev, "hclk");
> > > -       if (IS_ERR(chip->clk))
> > > -               return PTR_ERR(chip->clk);
> > > +       if (IS_ERR(chip->clk)) {
> > > +               if (PTR_ERR(chip->clk) == -ENOENT)
> > > +                       chip->clk = NULL;
> > 
> > You don't need to set it to NULL, if CONFIG_HAVE_CLK isn't set
> > the dummy routines would take care of it.
> 
> Yeah, but in our case we have CONFIG_HAVE_CLK=y and no clk is provided
> since IP is clockless. What could you suggest to do in such case?

	chip->clk = devm_clk_get(chip->dev, "hclk");
	if (IS_ERR(chip->clk) && PTR_ERR(chip->clk) != -ENOENT)
		return PTR_ERR(chip->clk);

You can then test for the presence of a clk via IS_ERR(chip->clk).

I'm just debating whether we should add a clk_is_valid() inline function
to linux/clk.h to avoid these shouting tests, and make it easier for
people test this in a generic manner.

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