Re: [PATCH v9 08/12] device core: Introduce DMA range map, supplanting dma_pfn_offset

[Nicolas Saenz Julienne <nsaenzjulienne@suse.de>]

Hi Jim, here's some comments after testing your series against RPi4.

On Fri, 2020-07-24 at 16:33 -0400, Jim Quinlan wrote:
> The new field 'dma_range_map' in struct device is used to facilitate the
> use of single or multiple offsets between mapping regions of cpu addrs and
> dma addrs.  It subsumes the role of "dev->dma_pfn_offset" which was only
> capable of holding a single uniform offset and had no region bounds
> checking.
> 
> The function of_dma_get_range() has been modified so that it takes a single
> argument -- the device node -- and returns a map, NULL, or an error code.
> The map is an array that holds the information regarding the DMA regions.
> Each range entry contains the address offset, the cpu_start address, the
> dma_start address, and the size of the region.
> 
> of_dma_configure() is the typical manner to set range offsets but there are
> a number of ad hoc assignments to "dev->dma_pfn_offset" in the kernel
> driver code.  These cases now invoke the function
> dma_attach_offset_range(dev, cpu_addr, dma_addr, size).
> 
> Signed-off-by: Jim Quinlan <james.quinlan@broadcom.com>
> ---

[...]

> diff --git a/drivers/of/address.c b/drivers/of/address.c
> index 8eea3f6e29a4..4b718d199efe 100644
> --- a/drivers/of/address.c
> +++ b/drivers/of/address.c
> @@ -918,33 +918,33 @@ void __iomem *of_io_request_and_map(struct device_node *np, int index,
>  }
>  EXPORT_SYMBOL(of_io_request_and_map);
>  
> +#ifdef CONFIG_HAS_DMA
>  /**
> - * of_dma_get_range - Get DMA range info
> + * of_dma_get_range - Get DMA range info and put it into a map array
>   * @np:		device node to get DMA range info
> - * @dma_addr:	pointer to store initial DMA address of DMA range
> - * @paddr:	pointer to store initial CPU address of DMA range
> - * @size:	pointer to store size of DMA range
> + * @map:	dma range structure to return
>   *
>   * Look in bottom up direction for the first "dma-ranges" property
> - * and parse it.
> - *  dma-ranges format:
> + * and parse it.  Put the information into a DMA offset map array.
> + *
> + * dma-ranges format:
>   *	DMA addr (dma_addr)	: naddr cells
>   *	CPU addr (phys_addr_t)	: pna cells
>   *	size			: nsize cells
>   *
> - * It returns -ENODEV if "dma-ranges" property was not found
> - * for this device in DT.
> + * It returns -ENODEV if "dma-ranges" property was not found for this
> + * device in the DT.
>   */
> -int of_dma_get_range(struct device_node *np, u64 *dma_addr, u64 *paddr, u64 *size)
> +int of_dma_get_range(struct device_node *np, const struct bus_dma_region **map)
>  {
>  	struct device_node *node = of_node_get(np);
>  	const __be32 *ranges = NULL;
> -	int len;
> -	int ret = 0;
>  	bool found_dma_ranges = false;
>  	struct of_range_parser parser;
>  	struct of_range range;
> -	u64 dma_start = U64_MAX, dma_end = 0, dma_offset = 0;
> +	struct bus_dma_region *r;
> +	int len, num_ranges = 0;
> +	int ret;
>  
>  	while (node) {
>  		ranges = of_get_property(node, "dma-ranges", &len);
> @@ -970,44 +970,35 @@ int of_dma_get_range(struct device_node *np, u64 *dma_addr, u64 *paddr, u64 *siz
>  	}
>  
>  	of_dma_range_parser_init(&parser, node);
> +	for_each_of_range(&parser, &range)
> +		num_ranges++;
> +
> +	of_dma_range_parser_init(&parser, node);
> +
> +	ret = -ENOMEM;
> +	r = kcalloc(num_ranges + 1, sizeof(*r), GFP_KERNEL);
> +	if (!r)
> +		goto out;
>  
> +	/*
> +	 * Record all info in the generic DMA ranges array for struct device.
> +	 */
> +	*map = r;
>  	for_each_of_range(&parser, &range) {
>  		pr_debug("dma_addr(%llx) cpu_addr(%llx) size(%llx)\n",
>  			 range.bus_addr, range.cpu_addr, range.size);
> -
> -		if (dma_offset && range.cpu_addr - range.bus_addr != dma_offset) {
> -			pr_warn("Can't handle multiple dma-ranges with different offsets on node(%pOF)\n", node);
> -			/* Don't error out as we'd break some existing DTs */
> -			continue;
> -		}
> -		dma_offset = range.cpu_addr - range.bus_addr;
> -
> -		/* Take lower and upper limits */
> -		if (range.bus_addr < dma_start)
> -			dma_start = range.bus_addr;
> -		if (range.bus_addr + range.size > dma_end)
> -			dma_end = range.bus_addr + range.size;
> -	}
> -
> -	if (dma_start >= dma_end) {
> -		ret = -EINVAL;
> -		pr_debug("Invalid DMA ranges configuration on node(%pOF)\n",
> -			 node);
> -		goto out;
> +		r->cpu_start = range.cpu_addr;
> +		r->dma_start = range.bus_addr;
> +		r->size = range.size;
> +		r->offset = (u64)range.cpu_addr - (u64)range.bus_addr;
> +		r++;
>  	}
>  
> -	*dma_addr = dma_start;
> -	*size = dma_end - dma_start;
> -	*paddr = dma_start + dma_offset;
> -
> -	pr_debug("final: dma_addr(%llx) cpu_addr(%llx) size(%llx)\n",
> -		 *dma_addr, *paddr, *size);
> -

I think you're missing here:

	ret = 0;

>  out:
>  	of_node_put(node);
> -
>  	return ret;
>  }

Regards,
Nicolas

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