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Message-Id: <8E74008F-6953-4BDC-8A56-F433AE947D30@konsulko.com>
Date: Thu, 24 Nov 2016 18:05:50 +0200
From: Pantelis Antoniou <pantelis.antoniou@...sulko.com>
To: Stephen Boyd <stephen.boyd@...aro.org>
Cc: Rob Herring <robh+dt@...nel.org>,
Frank Rowand <frowand.list@...il.com>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
"linux-kernel @ vger . kernel . org" <linux-kernel@...r.kernel.org>,
devicetree@...r.kernel.org, linux-gpio@...r.kernel.org,
Linus Walleij <linus.walleij@...aro.org>,
Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH 1/3] of: Support parsing phandle argument lists through a nexus node
Hi Stephen,
> On Nov 24, 2016, at 12:25 , Stephen Boyd <stephen.boyd@...aro.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 GPIO_ACTIVE_LOW &soc_gpio1 1 GPIO_ACTIVE_LOW>,
> <1 GPIO_ACTIVE_LOW &soc_gpio2 4 GPIO_ACTIVE_LOW>,
> <2 GPIO_ACTIVE_LOW &soc_gpio1 3 GPIO_ACTIVE_LOW>,
> <3 GPIO_ACTIVE_LOW &soc_gpio2 2 GPIO_ACTIVE_LOW>;
> gpio-map-mask = <0xf 0x1>;
> };
>
> expansion_device {
> reset-gpios = <&connector 2 GPIO_ACTIVE_LOW>;
> };
>
> 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>.
>
Very good. My only point would be to elaborate a little bit on the
documentation part about how there might be different #list-cells values
pointed at, and how the lookup is performed in steps.
> Cc: Pantelis Antoniou <pantelis.antoniou@...sulko.com>
> Cc: Linus Walleij <linus.walleij@...aro.org>
> Cc: Mark Brown <broonie@...nel.org>
> Signed-off-by: Stephen Boyd <stephen.boyd@...aro.org>
> ---
> drivers/of/base.c | 146 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/of.h | 14 +++++
> 2 files changed, 160 insertions(+)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index d687e6de24a0..693b73f33675 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -1772,6 +1772,152 @@ 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
> + * @cells_name: property name that specifies 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.
> + *
> + * 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-cells", "list-map",
> + * "list-map-mask", 1, &args);
> + */
> +int of_parse_phandle_with_args_map(const struct device_node *np,
> + const char *list_name,
> + const char *cells_name,
> + const char *map_name,
> + const char *mask_name,
> + int index, struct of_phandle_args *out_args)
> +{
> + struct device_node *cur, *new = NULL;
> + const __be32 *map, *mask, *tmp;
> + const __be32 dummy_mask[] = { [0 ... MAX_PHANDLE_ARGS] = ~0 };
> + __be32 initial_match_array[MAX_PHANDLE_ARGS];
> + const __be32 *match_array = initial_match_array;
> + int i, ret, map_len, match;
> + u32 list_size, new_size;
> +
> + if (index < 0)
> + return -EINVAL;
> +
> + ret = __of_parse_phandle_with_args(np, list_name, cells_name, 0, index,
> + out_args);
> + if (ret)
> + return ret;
> +
> + /* Get the #<list>-cells property */
> + cur = out_args->np;
> + ret = of_property_read_u32(cur, cells_name, &list_size);
> + if (ret < 0)
> + goto fail;
> +
> + /* 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]);
> +
> + while (cur) {
> + /* Get the <list>-map property */
> + map = of_get_property(cur, map_name, &map_len);
> + if (!map)
> + return 0;
> + 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 fail;
> +
> + if (!of_device_is_available(new))
> + match = 0;
> +
> + tmp = of_get_property(new, cells_name, NULL);
> + if (!tmp)
> + goto fail;
> +
> + new_size = be32_to_cpu(*tmp);
> +
> + /* Check for malformed properties */
> + if (WARN_ON(new_size > MAX_PHANDLE_ARGS))
> + goto fail;
> + if (map_len < new_size)
> + goto fail;
> +
> + /* Move forward by new node's #<list>-cells amount */
> + map += new_size;
> + map_len -= new_size;
> + }
> + if (!match)
> + goto fail;
> +
> + /*
> + * Successfully parsed a <list>-map translation; copy new
> + * specifier into the out_args structure.
> + */
> + match_array = map - new_size;
> + for (i = 0; i < new_size; i++)
> + out_args->args[i] = be32_to_cpup(map - new_size + i);
> + out_args->args_count = list_size = new_size;
> + /* Iterate again with new provider */
> + out_args->np = new;
> + of_node_put(cur);
> + cur = new;
> + }
> +fail:
> + of_node_put(cur);
> + of_node_put(new);
> +
> + return -EINVAL;
> +}
> +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
> diff --git a/include/linux/of.h b/include/linux/of.h
> index d3a9c2e69001..65ff306403a2 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -344,6 +344,9 @@ extern struct device_node *of_parse_phandle(const struct device_node *np,
> extern int of_parse_phandle_with_args(const struct device_node *np,
> const char *list_name, const char *cells_name, int index,
> struct of_phandle_args *out_args);
> +extern int of_parse_phandle_with_args_map(const struct device_node *np,
> + const char *list_name, const char *cells_name, const char *map_name,
> + const char *mask_name, int index, struct of_phandle_args *out_args);
> extern int of_parse_phandle_with_fixed_args(const struct device_node *np,
> const char *list_name, int cells_count, int index,
> struct of_phandle_args *out_args);
> @@ -738,6 +741,17 @@ static inline int of_parse_phandle_with_args(const struct device_node *np,
> return -ENOSYS;
> }
>
> +static inline int of_parse_phandle_with_args_map(const struct device_node *np,
> + const char *list_name,
> + const char *cells_name,
> + const char *map_name,
> + const char *mask_name,
> + int index,
> + struct of_phandle_args *out_args)
> +{
> + return -ENOSYS;
> +}
> +
> static inline int of_parse_phandle_with_fixed_args(const struct device_node *np,
> const char *list_name, int cells_count, int index,
> struct of_phandle_args *out_args)
> --
> 2.10.0.297.gf6727b0
>
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