> Date: Sun, 3 Apr 2016 16:57:10 +0200 > From: Patrick Wildt <patr...@blueri.se> > > 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 > >