Subject: Re: [RFC 5/5] [powerpc] Implement a p1010rdb clock source.

From: Wolfgang Grandegger <[email-masked]>
Date: Mon, 08 Aug 2011 10:37:58 +0200

On 08/06/2011 04:34 PM, Robin Holt wrote:
> flexcan driver needs the clk_get, clk_get_rate, etc functions
> to work.  This patch provides the minimum functionality.

This needs some more general thoughts... apart from the question where
the code should go.

Like for the MSCAN on the MPC5200, the user should be *able* to select
an appropriate clock source and divider via DTS node properties.
Currently it seems, that the DTS properties must match some
pre-configured values, most likely set by the boot loader. Please
correct me if I'm wrong. For me this is generic and should go into the
Flexcan driver. From there, a platform specific function, e.g.
flexcan_set_clock() might be called.

> Signed-off-by: Robin Holt <holt-sJ/[email-masked]>
> To: Marc Kleine-Budde <[email-masked]>
> To: Wolfgang Grandegger <[email-masked]>
> To: U Bhaskar-B22300 <[email-masked]>
> Cc: [email-masked]
> Cc: [email-masked]
> ---
>  arch/powerpc/platforms/85xx/p1010rdb.c |   78 ++++++++++++++++++++++++++++++++
>  1 files changed, 78 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/85xx/p1010rdb.c b/arch/powerpc/platforms/85xx/p1010rdb.c
> index 3540a88..8f78ddd 100644
> --- a/arch/powerpc/platforms/85xx/p1010rdb.c
> +++ b/arch/powerpc/platforms/85xx/p1010rdb.c
> @@ -28,6 +28,7 @@
>  #include <asm/udbg.h>
>  #include <asm/mpic.h>
>  #include <asm/swiotlb.h>
> +#include <asm/clk_interface.h>
>  
>  #include <sysdev/fsl_soc.h>
>  #include <sysdev/fsl_pci.h>
> @@ -164,6 +165,82 @@ static void __init p1010_rdb_setup_arch(void)
>  	printk(KERN_INFO "P1010 RDB board from Freescale Semiconductor\n");
>  }
>  
> +/*
> + * p1010rdb needs to provide a clock source for the flexcan driver.
> + */
> +struct clk {
> +	unsigned long rate;
> +} p1010rdb_system_clk;
> +
> +static struct clk *p1010_rdb_clk_get(struct device *dev, const char *id)
> +{

I persoanlly don't like the

> +	struct clk *clk;
> +	u32 *of_property;
> +	unsigned long clock_freq, clock_divider;
> +	const char *dev_init_name;
> +
> +	if (!dev)
> +		return ERR_PTR(-ENOENT);
> +
> +	/*
> +	 * The can devices are named ffe1c000.can0 and ffe1d000.can1 on
> +	 * the p1010rdb.  Check for the "can" portion of that name before
> +	 * returning a clock source.
> +	 */
> +	dev_init_name = dev_name(dev);
> +	if (strlen(dev_init_name) != 13)
> +		return ERR_PTR(-ENOENT);
> +	dev_init_name += 9;
> +	if (strncmp(dev_init_name, "can", 3))
> +		return ERR_PTR(-ENOENT);

There are dedicated functions to find the of node. But with my above
proposal we do not need to provide p1010_rdb_clk_get().

More comments on the other patches soon...

Wolfgang.