> Date: Sun, 3 Apr 2016 16:57:10 +0200
> From: Patrick Wildt <[email protected]>
>
> Hi,
>
> now we're able to get a node's memory address. Though, a device tree
> may implement so called ranges. Those ranges are used to translate from
> one address space to another.
>
> This is used on a few machines, for instance on the raspberry pi:
>
> / {
> #address-cells = <0x1>;
> #size-cells = <0x1>;
> interrupt-parent = <0x1>;
> compatible = "brcm,bcm2710", "brcm,bcm2709";
> model = "Raspberry Pi 3 Model B";
> [...]
> soc {
> compatible = "simple-bus";
> #address-cells = <0x1>;
> #size-cells = <0x1>;
> ranges = <0x7e000000 0x3f000000 0x1000000>;
> [...]
> interrupt-controller@7e00b200 {
> compatible = "brcm,bcm2708-armctrl-ic";
> reg = <0x7e00b200 0x200>;
> interrupt-controller;
> #interrupt-cells = <0x2>;
> linux,phandle = <0x1>;
> phandle = <0x1>;
> };
>
> Even though the node's reg is set to 0x7e00b200, the actual address is
> 0x3f00b200. To get to that address, we need to check the parent's
> ranges attribute.
>
> Since I last posted this diff in another thread I have added an
> explanatory comment before the function and improved a few comments
> inline.
>
> ok?
Is the
> + if (node == NULL || mem == NULL)
check really necessary?
Also I wonder if it would make sense to return an errno value upon
failure instead of 1. That makes it immediately obvious that the
function returns 0 upon success.
> diff --git sys/dev/ofw/fdt.c sys/dev/ofw/fdt.c
> index c430a1e..8990afc 100644
> --- sys/dev/ofw/fdt.c
> +++ sys/dev/ofw/fdt.c
> @@ -34,6 +34,7 @@ void *skip_node(void *);
> void *fdt_parent_node_recurse(void *, void *);
> int fdt_node_property_int(void *, char *, int *);
> int fdt_node_property_ints(void *, char *, int *, int);
> +int fdt_translate_memory_address(void *, struct fdt_memory *);
> #ifdef DEBUG
> void fdt_print_node_recurse(void *, int);
> #endif
> @@ -390,6 +391,108 @@ fdt_parent_node(void *node)
> }
>
> /*
> + * Translate memory address depending on parent's range.
> + *
> + * Ranges are a way of mapping one address to another. This ranges attribute
> + * is set on a node's parent. This means if a node does not have a parent,
> + * there's nothing to translate. If it does have a parent and the parent
> does
> + * not have a ranges attribute, there's nothing to translate either.
> + *
> + * If the parent has a ranges attribute and the attribute is not empty, the
> + * node's memory address has to be in one of the given ranges. This range is
> + * then used to translate the memory address.
> + *
> + * If the parent has a ranges attribute, but the attribute is empty, there's
> + * nothing to translate. But it's not a translation barrier. It can be
> treated
> + * as a simple 1:1 mapping.
> + *
> + * Translation does not end here. We need to check if the parent's parent
> also
> + * has a ranges attribute and ask the same questions again.
> + */
> +int
> +fdt_translate_memory_address(void *node, struct fdt_memory *mem)
> +{
> + void *parent;
> + int pac, psc, ac, sc, ret, rlen, rone, *range;
> + uint64_t from, to, size;
> +
> + if (node == NULL || mem == NULL)
> + return 1;
> +
> + /* No parent, no translation. */
> + parent = fdt_parent_node(node);
> + if (parent == NULL)
> + return 0;
> +
> + /* Extract ranges property from node. */
> + rlen = fdt_node_property(node, "ranges", (char **)&range) / sizeof(int);
> +
> + /* No ranges means translation barrier. Translation stops here. */
> + if (range == NULL)
> + return 0;
> +
> + /* Empty ranges means 1:1 mapping. Continue translation on parent. */
> + if (rlen <= 0)
> + return fdt_translate_memory_address(parent, mem);
> +
> + /* We only support 32-bit (1), and 64-bit (2) wide addresses here. */
> + ret = fdt_node_property_int(parent, "#address-cells", &pac);
> + if (ret != 1 || pac <= 0 || pac > 2)
> + return 1;
> +
> + /* We only support 32-bit (1), and 64-bit (2) wide sizes here. */
> + ret = fdt_node_property_int(parent, "#size-cells", &psc);
> + if (ret != 1 || psc <= 0 || psc > 2)
> + return 1;
> +
> + /* We only support 32-bit (1), and 64-bit (2) wide addresses here. */
> + ret = fdt_node_property_int(node, "#address-cells", &ac);
> + if (ret <= 0)
> + ac = pac;
> + else if (ret > 1 || ac <= 0 || ac > 2)
> + return 1;
> +
> + /* We only support 32-bit (1), and 64-bit (2) wide sizes here. */
> + ret = fdt_node_property_int(node, "#size-cells", &sc);
> + if (ret <= 0)
> + sc = psc;
> + else if (ret > 1 || sc <= 0 || sc > 2)
> + return 1;
> +
> + /* Must have at least one range. */
> + rone = pac + ac + sc;
> + if (rlen < rone)
> + return 1;
> +
> + /* For each range. */
> + for (; rlen >= rone; rlen -= rone, range += rone) {
> + /* Extract from and size, so we can see if we fit. */
> + from = betoh32(range[0]);
> + if (ac == 2)
> + from = (from << 32) + betoh32(range[1]);
> + size = betoh32(range[ac + pac]);
> + if (sc == 2)
> + size = (size << 32) + betoh32(range[ac + pac + 1]);
> +
> + /* Try next, if we're not in the range. */
> + if (mem->addr < from || (mem->addr + mem->size) > (from + size))
> + continue;
> +
> + /* All good, extract to address and translate. */
> + to = betoh32(range[ac]);
> + if (pac == 2)
> + to = (to << 32) + betoh32(range[ac + 1]);
> +
> + mem->addr -= from;
> + mem->addr += to;
> + return fdt_translate_memory_address(parent, mem);
> + }
> +
> + /* To be successful, we must have returned in the for-loop. */
> + return 1;
> +}
> +
> +/*
> * Parse the memory address and size of a node.
> */
> int
> @@ -429,10 +532,7 @@ fdt_get_memory_address(void *node, int idx, struct
> fdt_memory *mem)
> if (sc == 2)
> mem->size = (mem->size << 32) + betoh32(in[off + ac + 1]);
>
> - /* TODO: translate memory address in ranges */
> - //return fdt_translate_memory_address(parent, mem);
> -
> - return 0;
> + return fdt_translate_memory_address(parent, mem);
> }
>
> #ifdef DEBUG
>
>
