Re: [PATCH v2 3/3] hwrng: meson: add clock handling to driver

[Neil Armstrong <narmstrong-rdvid1DuHRBWk0Htik3J/w@public.gmane.org>]

On 02/21/2017 12:26 PM, Heiner Kallweit wrote:
> Add handling of RNG0 clock to the driver.
> 
> Signed-off-by: Heiner Kallweit <hkallweit1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
> v2:
> - consider that clock is optional
> - use managed call to clk_disable_unprepare to ensure that
>   cleaning up is done in the right order if driver is removed
> ---
>  drivers/char/hw_random/meson-rng.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/drivers/char/hw_random/meson-rng.c b/drivers/char/hw_random/meson-rng.c
> index 119d6984..2e23be80 100644
> --- a/drivers/char/hw_random/meson-rng.c
> +++ b/drivers/char/hw_random/meson-rng.c
> @@ -62,6 +62,7 @@
>  #include <linux/slab.h>
>  #include <linux/types.h>
>  #include <linux/of.h>
> +#include <linux/clk.h>
>  
>  #define RNG_DATA 0x00
>  
> @@ -69,6 +70,7 @@ struct meson_rng_data {
>  	void __iomem *base;
>  	struct platform_device *pdev;
>  	struct hwrng rng;
> +	struct clk *core_clk;
>  };
>  
>  static int meson_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> @@ -81,11 +83,17 @@ static int meson_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
>  	return sizeof(u32);
>  }
>  
> +static void meson_rng_clk_disable(void *clk)
> +{
> +	clk_disable_unprepare(clk);
> +}
> +
>  static int meson_rng_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
>  	struct meson_rng_data *data;
>  	struct resource *res;
> +	int ret;
>  
>  	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
>  	if (!data)
> @@ -98,6 +106,20 @@ static int meson_rng_probe(struct platform_device *pdev)
>  	if (IS_ERR(data->base))
>  		return PTR_ERR(data->base);
>  
> +	data->core_clk = devm_clk_get(dev, "core");
> +	if (IS_ERR(data->core_clk))
> +		data->core_clk = NULL;
> +
> +	if (data->core_clk) {

This "if" is useless, if core_clk is NULL, this will work also.

> +		ret = clk_prepare_enable(data->core_clk);
> +		if (ret)
> +			return ret;
> +		ret = devm_add_action_or_reset(dev, meson_rng_clk_disable,
> +					       data->core_clk);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	data->rng.name = pdev->name;
>  	data->rng.read = meson_rng_read;
>  
> 

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