Subject: [Linaro-mm-sig] [PATCH 2/2] drivers: dma-contiguous: add initialization from device tree

From: [email-masked] (Laura Abbott)
Date: Thu, 14 Feb 2013 13:34:34 -0800

Hi,

On 2/14/2013 4:45 AM, Marek Szyprowski wrote:
<snip>
> +name:		an name given to the defined region.
> +base-address:	the base address of the defined region.
> +size:		the size of the memory region.
> +linux,contiguous-region: property indicating that the defined memory
> +		region is used for contiguous memory allocations,
> +		Linux specific (optional)
> +linux,default-contiguous-region: property indicating that the region
> +		is the default region for all contiguous memory
> +		allocations, Linux specific (optional)
> +
> +

I don't see any code actually implementing the default-contiguous-region 
binding. Currently on ARM systems we will still setup the default region 
based on the Kconfig. Is this intentional?

> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index 085389c..5761f73 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -24,6 +24,9 @@
>
>   #include <linux/memblock.h>
>   #include <linux/err.h>
> +#include <linux/of.h>
> +#include <linux/of_fdt.h>
> +#include <linux/of_platform.h>
>   #include <linux/mm.h>
>   #include <linux/mutex.h>
>   #include <linux/page-isolation.h>
> @@ -177,6 +180,35 @@ no_mem:
>   	return ERR_PTR(ret);
>   }
>
> +/*****************************************************************************/
> +
> +#ifdef CONFIG_OF
> +int __init cma_fdt_scan(unsigned long node, const char *uname,
> +				int depth, void *data)
> +{
> +	phys_addr_t base, size;
> +	unsigned long len;
> +	__be32 *prop;
> +
> +	if (strncmp(uname, "region@", 7) != 0 || depth != 2 ||
> +	    !of_get_flat_dt_prop(node, "contiguous-region", NULL))

The documentation says "linux,contiguous-region"

> +#ifdef CONFIG_OF
> +static void cma_assign_device_from_dt(struct device *dev)
> +{
> +	struct device_node *node;
> +	struct cma *cma;
> +	u32 value;
> +
> +	node = of_parse_phandle(dev->of_node, "linux,contiguous-region", 0);
> +	if (!node)
> +		return;
> +	if (of_property_read_u32(node, "reg", &value) && !value)
> +		return;
> +	cma = cma_get_area(value);
> +	if (!cma)
> +		return;
> +
> +	dev_set_cma_area(dev, cma);
> +	pr_info("Assigned CMA region at %lx to %s device\n", (unsigned long)value, dev_name(dev));
> +}
> +

This scheme of associating devices with CMA regions by base does not 
work if you want to let CMA figure out where to place the region (base = 
0). Can we use the name to associate the device with the region? I had 
been working on something similar internally and that was the only 
solution I had come up with to associate arbitrary CMA nodes with devices.

Thanks,
Laura

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