Subject: Re: [PATCH v11 5/6] flexcan: Prefer device tree clock frequency if available.

From: Marc Kleine-Budde <[email-masked]>
Date: Thu, 11 Aug 2011 18:18:20 +0200

On 08/11/2011 06:07 PM, Robin Holt wrote:
> If our CAN device's device tree node has a clock-frequency property,
> then use that value for the can devices clock frequency.  If not, fall
> back to asking the platform/mach code for the clock frequency associated
> with the flexcan device.

nitpicking follows inline:

> Signed-off-by: Robin Holt <holt-sJ/[email-masked]>
> To: Kumar Gala <[email-masked]>
> To: Wolfgang Grandegger <[email-masked]>,
> To: Marc Kleine-Budde <[email-masked]>,
> To: U Bhaskar-B22300 <[email-masked]>
> To: Scott Wood <[email-masked]>
> To: Grant Likely <grant.likely-s3s/[email-masked]>
> Cc: [email-masked],
> Cc: [email-masked],
> Cc: PPC list <linuxppc-dev-uLR06cmDAlY/[email-masked]>
> Cc: devicetree-discuss-uLR06cmDAlY/[email-masked]
> ---
>  .../devicetree/bindings/net/can/fsl-flexcan.txt    |    2 +
>  drivers/net/can/flexcan.c                          |   33 +++++++++++++++-----
>  2 files changed, 27 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/net/can/fsl-flexcan.txt b/Documentation/devicetree/bindings/net/can/fsl-flexcan.txt
> index c78dcbb..a4382c7 100644
> --- a/Documentation/devicetree/bindings/net/can/fsl-flexcan.txt
> +++ b/Documentation/devicetree/bindings/net/can/fsl-flexcan.txt
> @@ -11,6 +11,7 @@ Required properties:
>  
>  - reg : Offset and length of the register set for this device
>  - interrupts : Interrupt tuple for this device
> +- clock-frequency : The oscillator frequency driving the flexcan device
>  
>  Example:
>  
> @@ -19,4 +20,5 @@ Example:
>            reg = <0x1c000 0x1000>;
>            interrupts = <48 0x2>;
>            interrupt-parent = <&mpic>;
> +          clock-frequency = <0x0bebc1fc>;

Does the device tree support dec coded integers? IMHO a frequency is
best expressed in decimal.

>    };
> diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
> index 662f832..d40c38e 100644
> --- a/drivers/net/can/flexcan.c
> +++ b/drivers/net/can/flexcan.c
> @@ -33,6 +33,7 @@
>  #include <linux/kernel.h>
>  #include <linux/list.h>
>  #include <linux/module.h>
> +#include <linux/of.h>
>  #include <linux/platform_device.h>
>  
>  #define DRV_NAME			"flexcan"
> @@ -929,12 +930,26 @@ static int __devinit flexcan_probe(struct platform_device *pdev)
>  	void __iomem *base;
>  	resource_size_t mem_size;
>  	int err, irq;
> +	u32 clock_freq = 0;
>  
> -	clk = clk_get(&pdev->dev, NULL);
> -	if (IS_ERR(clk)) {
> -		dev_err(&pdev->dev, "no clock defined\n");
> -		err = PTR_ERR(clk);
> -		goto failed_clock;
> +	if (pdev->dev.of_node) {
> +		const u32 *clock_freq_p;
> +
> +		clk = NULL;

Hmmm - what about moving the clk = NULL into the definition of clk?

> +		clock_freq_p = of_get_property(pdev->dev.of_node,
> +						"clock-frequency", NULL);
> +		if (clock_freq_p)
> +			clock_freq = *clock_freq_p;
> +	}
> +
> +	if (!clock_freq) {
> +		clk = clk_get(&pdev->dev, NULL);
> +		if (IS_ERR(clk)) {
> +			dev_err(&pdev->dev, "no clock defined\n");
> +			err = PTR_ERR(clk);
> +			goto failed_clock;
> +		}
> +		clock_freq = clk_get_rate(clk);
>  	}
>  
>  	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> @@ -967,7 +982,7 @@ static int __devinit flexcan_probe(struct platform_device *pdev)
>  	dev->flags |= IFF_ECHO; /* we support local echo in hardware */
>  
>  	priv = netdev_priv(dev);
> -	priv->can.clock.freq = clk_get_rate(clk);
> +	priv->can.clock.freq = clock_freq;
>  	priv->can.bittiming_const = &flexcan_bittiming_const;
>  	priv->can.do_set_mode = flexcan_set_mode;
>  	priv->can.do_get_berr_counter = flexcan_get_berr_counter;
> @@ -1002,7 +1017,8 @@ static int __devinit flexcan_probe(struct platform_device *pdev)
>   failed_map:
>  	release_mem_region(mem->start, mem_size);
>   failed_get:
> -	clk_put(clk);
> +	if (clk)
> +		clk_put(clk);
>   failed_clock:
>  	return err;
>  }
> @@ -1020,7 +1036,8 @@ static int __devexit flexcan_remove(struct platform_device *pdev)
>  	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	release_mem_region(mem->start, resource_size(mem));
>  
> -	clk_put(priv->clk);
> +	if (priv->clk)
> +		clk_put(priv->clk);
>  
>  	free_candev(dev);
>  

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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