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SubjectRe: [PATCH] dmaengine: dw: support for clockless platforms
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On Wed, 2015-02-11 at 12:07 +0000, Russell King - ARM Linux wrote:
> 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.

I guess clock framework may handle whatever is gotten from clk_get().
In driver much cleaner to use direct calls with exceptions (like you
can't get a valid clock rate from non-existing clock).
So, what about just passing by the error code and doing nothing?

--
Andy Shevchenko <andriy.shevchenko@intel.com>
Intel Finland Oy



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