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

[Rob Herring <robh+dt@kernel.org>]

On Fri, Jul 24, 2020 at 2:45 PM Jim Quinlan <james.quinlan@broadcom.com> 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;

AFAICT, you have the error cases covered, but you are leaking memory
if the device is removed.

[...]

> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index 9f04c30c4aaf..49242dd6176e 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -519,7 +519,7 @@ static int rproc_handle_vdev(struct rproc *rproc, struct fw_rsc_vdev *rsc,
>         /* Initialise vdev subdevice */
>         snprintf(name, sizeof(name), "vdev%dbuffer", rvdev->index);
>         rvdev->dev.parent = &rproc->dev;
> -       rvdev->dev.dma_pfn_offset = rproc->dev.parent->dma_pfn_offset;
> +       rvdev->dev.dma_range_map = rproc->dev.parent->dma_range_map;

But doing this means you can't just free the dma_range_map. You need
to do a copy here or you'd have to refcount it. Or I suppose you could
check if it the child has a different dma_range_map ptr than the
parent.

Rob
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