On Tue, Jan 17, 2017 at 6:50 PM, Stephen Boyd <stephen.b...@linaro.org> wrote: > Platforms like 96boards have a standardized connector/expansion > slot that exposes signals like GPIOs to expansion boards in an > SoC agnostic way. We'd like the DT overlays for the expansion > boards to be written once without knowledge of the SoC on the > other side of the connector. This avoids the unscalable > combinatorial explosion of a different DT overlay for each > expansion board and SoC pair. > > We need a way to describe the GPIOs routed through the connector > in an SoC agnostic way. Let's introduce nexus property parsing > into the OF core to do this. This is largely based on the > interrupt nexus support we already have. This allows us to remap > a phandle list in a consumer node (e.g. reset-gpios) through a > connector in a generic way (e.g. via gpio-map). Do this in a > generic routine so that we can remap any sort of variable length > phandle list. > > Taking GPIOs as an example, the connector would be a GPIO nexus, > supporting the remapping of a GPIO specifier space to multiple > GPIO providers on the SoC. DT would look as shown below, where > 'soc_gpio1' and 'soc_gpio2' are inside the SoC, 'connector' is an > expansion port where boards can be plugged in, and > 'expansion_device' is a device on the expansion board. > > soc { > soc_gpio1: gpio-controller1 { > #gpio-cells = <2>; > }; > > soc_gpio2: gpio-controller2 { > #gpio-cells = <2>; > }; > }; > > connector: connector { > #gpio-cells = <2>; > gpio-map = <0 0 &soc_gpio1 1 0>, > <1 0 &soc_gpio2 4 0>, > <2 0 &soc_gpio1 3 0>, > <3 0 &soc_gpio2 2 0>; > gpio-map-mask = <0xf 0x0>; > gpio-map-pass-thru = <0x0 0x1> > }; > > expansion_device { > reset-gpios = <&connector 2 GPIO_ACTIVE_LOW>; > };
This all looks good to me. A few nits below. > > The GPIO core would use of_parse_phandle_with_args_map() instead > of of_parse_phandle_with_args() and arrive at the same type of > result, a phandle and argument list. The difference is that the > phandle and arguments will be remapped through the nexus node to > the underlying SoC GPIO controller node. In the example above, > we would remap 'reset-gpios' from <&connector 2 GPIO_ACTIVE_LOW> > to <&soc_gpio1 3 GPIO_ACTIVE_LOW>. > > Cc: Pantelis Antoniou <pantelis.anton...@konsulko.com> > Cc: Linus Walleij <linus.wall...@linaro.org> > Cc: Mark Brown <broo...@kernel.org> > Signed-off-by: Stephen Boyd <stephen.b...@linaro.org> > --- > drivers/of/base.c | 186 > +++++++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/of.h | 12 ++++ > 2 files changed, 198 insertions(+) > > diff --git a/drivers/of/base.c b/drivers/of/base.c > index d4bea3c797d6..277a81ff0479 100644 > --- a/drivers/of/base.c > +++ b/drivers/of/base.c > @@ -1775,6 +1775,192 @@ int of_parse_phandle_with_args(const struct > device_node *np, const char *list_na > EXPORT_SYMBOL(of_parse_phandle_with_args); > > /** > + * of_parse_phandle_with_args_map() - Find a node pointed by phandle in a > list and remap it > + * @np: pointer to a device tree node containing a list > + * @list_name: property name that contains a list > + * @stem_name: stem of property names that specify phandles' arguments count > + * @index: index of a phandle to parse out > + * @out_args: optional pointer to output arguments structure (will be > filled) > + * > + * This function is useful to parse lists of phandles and their arguments. > + * Returns 0 on success and fills out_args, on error returns appropriate > errno > + * value. The difference between this function and > of_parse_phandle_with_args() > + * is that this API remaps a phandle if the node the phandle points to has > + * a <@stem_name>-map property. > + * > + * Caller is responsible to call of_node_put() on the returned out_args->np > + * pointer. > + * > + * Example: > + * > + * phandle1: node1 { > + * #list-cells = <2>; > + * } > + * > + * phandle2: node2 { > + * #list-cells = <1>; > + * } > + * > + * phandle3: node3 { > + * #list-cells = <1>; > + * list-map = <0 &phandle2 3>, > + * <1 &phandle2 2>, > + * <2 &phandle1 5 1>; > + * list-map-mask = <0x3>; > + * }; > + * > + * node4 { > + * list = <&phandle1 1 2 &phandle3 0>; > + * } > + * > + * To get a device_node of the `node2' node you may call this: > + * of_parse_phandle_with_args(node4, "list", "list", 1, &args); > + */ > +int of_parse_phandle_with_args_map(const struct device_node *np, > + const char *list_name, > + const char *stem_name, > + int index, struct of_phandle_args > *out_args) > +{ > + char *cells_name, *map_name = NULL, *mask_name = NULL; > + char *pass_name = NULL; > + struct device_node *cur, *new = NULL; > + const __be32 *map, *mask, *pass, *tmp; > + const __be32 dummy_mask[] = { [0 ... MAX_PHANDLE_ARGS] = ~0 }; > + const __be32 dummy_pass[] = { [0 ... MAX_PHANDLE_ARGS] = 0 }; These could be static and save some stack space. > + __be32 initial_match_array[MAX_PHANDLE_ARGS]; We worked to get rid of this MAX_PHANDLE_ARGS limitation. I guess this is fine as I don't think we'll do an IOMMU thru a connector which is the main thing having long args list. > + const __be32 *match_array = initial_match_array; > + int i, ret, map_len, match; > + u32 list_size, new_size; > + > + if (index < 0) > + return -EINVAL; > + > + cells_name = kasprintf(GFP_KERNEL, "#%s-cells", stem_name); > + if (!cells_name) > + return -ENOMEM; > + > + ret = -ENOMEM; > + map_name = kasprintf(GFP_KERNEL, "%s-map", stem_name); > + if (!map_name) > + goto free; > + > + mask_name = kasprintf(GFP_KERNEL, "%s-map-mask", stem_name); > + if (!mask_name) > + goto free; > + > + pass_name = kasprintf(GFP_KERNEL, "%s-map-pass-thru", stem_name); > + if (!pass_name) > + goto free; > + > + ret = __of_parse_phandle_with_args(np, list_name, cells_name, 0, > index, > + out_args); > + if (ret) > + goto free; > + > + /* Get the #<list>-cells property */ > + cur = out_args->np; > + ret = of_property_read_u32(cur, cells_name, &list_size); > + if (ret < 0) > + goto put; > + > + /* Precalculate the match array - this simplifies match loop */ > + for (i = 0; i < list_size; i++) > + initial_match_array[i] = cpu_to_be32(out_args->args[i]); > + > + ret = -EINVAL; > + while (cur) { > + /* Get the <list>-map property */ > + map = of_get_property(cur, map_name, &map_len); > + if (!map) { > + ret = 0; > + goto free; > + } > + map_len /= sizeof(u32); > + > + /* Get the <list>-map-mask property (optional) */ > + mask = of_get_property(cur, mask_name, NULL); > + if (!mask) > + mask = dummy_mask; > + /* Iterate through <list>-map property */ > + match = 0; > + while (map_len > (list_size + 1) && !match) { > + /* Compare specifiers */ > + match = 1; > + for (i = 0; i < list_size; i++, map_len--) > + match &= !((match_array[i] ^ *map++) & > mask[i]); > + > + of_node_put(new); > + new = of_find_node_by_phandle(be32_to_cpup(map)); > + map++; > + map_len--; > + > + /* Check if not found */ > + if (!new) > + goto put; > + > + if (!of_device_is_available(new)) > + match = 0; > + > + tmp = of_get_property(new, cells_name, NULL); > + if (!tmp) > + goto put; > + > + new_size = be32_to_cpu(*tmp); This can use of_property_read_u32. > + > + /* Check for malformed properties */ > + if (WARN_ON(new_size > MAX_PHANDLE_ARGS)) > + goto put; > + if (map_len < new_size) > + goto put; > + > + /* Move forward by new node's #<list>-cells amount */ > + map += new_size; > + map_len -= new_size; > + } > + if (!match) > + goto put; > + > + /* Get the <list>-map-pass-thru property (optional) */ > + pass = of_get_property(cur, pass_name, NULL); > + if (!pass) > + pass = dummy_pass; > + > + /* > + * Successfully parsed a <list>-map translation; copy new > + * specifier into the out_args structure, keeping the > + * bits specified in <list>-map-pass-thru. > + */ > + match_array = map - new_size; > + for (i = 0; i < new_size; i++) { > + __be32 val = *(map - new_size + i); > + > + if (i < list_size) { > + val &= ~pass[i]; > + val |= cpu_to_be32(out_args->args[i]) & > pass[i]; > + } > + > + out_args->args[i] = be32_to_cpu(val); > + } > + out_args->args_count = list_size = new_size; > + /* Iterate again with new provider */ > + out_args->np = new; > + of_node_put(cur); > + cur = new; > + } > +put: > + of_node_put(cur); > + of_node_put(new); > +free: > + kfree(mask_name); > + kfree(map_name); > + kfree(cells_name); > + kfree(pass_name); > + > + return ret; > +} > +EXPORT_SYMBOL(of_parse_phandle_with_args_map); > + > +/** > * of_parse_phandle_with_fixed_args() - Find a node pointed by phandle in a > list > * @np: pointer to a device tree node containing a list > * @list_name: property name that contains a list