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

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Date:	Wed, 11 Feb 2015 10:10:25 +0800
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Russell King <linux@....linux.org.uk>
Cc:	Andy Shevchenko <andriy.shevchenko@...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 Tue, Jan 20, 2015 at 8:57 PM, Heikki Krogerus
<heikki.krogerus@...ux.intel.com> wrote:
> When requesting clock in the platform driver, leaving
> chip->clk value as NULL if -ENOENT is returned, and
> continue. With other errors returning failure. It makes the
> driver usable on platforms that do not provide the clock.
>
> Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> ---
>  drivers/dma/dw/platform.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dma/dw/platform.c b/drivers/dma/dw/platform.c
> index 32ea1ac..b183bc0 100644
> --- a/drivers/dma/dw/platform.c
> +++ b/drivers/dma/dw/platform.c
> @@ -180,8 +180,12 @@ static int dw_probe(struct platform_device *pdev)
>         chip->dev = dev;
>
>         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;

This is wrong and reasons are mentioned in this thread:

http://lists.infradead.org/pipermail/linux-arm-kernel/2012-March/088437.html

You don't need to set it to NULL, if CONFIG_HAVE_CLK isn't set
the dummy routines would take care of it.
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