[PATCH 1/1] of: add dma-mask binding

[robherring2@gmail.com (Rob Herring)]

On 03/07/2012 05:26 AM, Jean-Christophe PLAGNIOL-VILLARD wrote:
> This will allow each device to specify its dma-mask
> The microblaze architecture hook is keep temporary if no dma-mask is specified
> int the DT
> 
> Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
> ---
>  drivers/of/platform.c |   26 +++++++++++++++++++++++++-
>  1 files changed, 25 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index cae9477..bb22194 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -121,6 +121,26 @@ void of_device_make_bus_id(struct device *dev)
>  	dev_set_name(dev, "%s.%d", node->name, magic - 1);
>  }
>  
> +static u64* of_get_dma_mask(struct device_node *np)
> +{
> +	const __be32 *prop;
> +	int len;
> +	u64 *dma_mask;
> +
> +	prop = of_get_property(np, "dma-mask", &len);

This would need some documentation. There is already "dma-ranges"
defined for OF which nay do what's needed.

> +
> +	if (!prop)
> +		return NULL;
> +
> +	dma_mask = kzalloc(sizeof(u64), GFP_KERNEL);

This seems kind of wasteful for 1 u64.

> +	if (!dma_mask)
> +		return NULL;
> +
> +	*dma_mask = of_read_number(prop, len / 4);
> +
> +	return dma_mask;
> +}
> +
>  /**
>   * of_device_alloc - Allocate and initialize an of_device
>   * @np: device node to assign to device
> @@ -161,10 +181,14 @@ struct platform_device *of_device_alloc(struct device_node *np,
>  		WARN_ON(of_irq_to_resource_table(np, res, num_irq) != num_irq);
>  	}
>  
> +	dev->dev.dma_mask = of_get_dma_mask(np);
>  	dev->dev.of_node = of_node_get(np);
> +
>  #if defined(CONFIG_MICROBLAZE)
> -	dev->dev.dma_mask = &dev->archdata.dma_mask;

And doing it this way for didn't get a warm reception either:

http://lists.ozlabs.org/pipermail/devicetree-discuss/2011-April/005285.html

Do you really need this to be something other than ~0UL and if so does
it need to be per device or system wide?

You can solve this with bus notifiers in your at91 code. Here's an
example which I did (but no longer need):

static u64 highbank_dma_mask = DMA_BIT_MASK(32);

static int highbank_platform_notifier(struct notifier_block *nb,
				  unsigned long event, void *__dev)
{
	struct device *dev = __dev;

	if (event != BUS_NOTIFY_ADD_DEVICE)
		return NOTIFY_DONE;

	if (of_device_is_compatible(dev->of_node, "calxeda,hb-nfc"))
		dev->dma_mask = &highbank_dma_mask;
	else
		return NOTIFY_DONE;

	return NOTIFY_OK;
}

static struct notifier_block highbank_platform_nb = {
	.notifier_call = highbank_platform_notifier,
};

int highbank_devices_init(void)
{
	return bus_register_notifier(&platform_bus_type, &highbank_platform_nb);
}

Rob

> +	if (!dev->dev.dma_mask)
> +		dev->dev.dma_mask = &dev->archdata.dma_mask;
>  #endif
> +
>  	dev->dev.parent = parent;
>  
>  	if (bus_id)