On Tue, Jan 17, 2017 at 6:50 PM, Stephen Boyd <stephen.boyd@xxxxxxxxxx> 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.antoniou@xxxxxxxxxxxx>
> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Cc: Mark Brown <broonie@xxxxxxxxxx>
> Signed-off-by: Stephen Boyd <stephen.boyd@xxxxxxxxxx>
> ---
> 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
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