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gpiolib: of: Handle threecell GPIO chips

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When describing GPIO controllers in the device tree, the ambition
of device tree to describe the hardware may require a three-cell
scheme:

gpios = <&gpio instance offset flags>;

This implements support for this scheme in the gpiolib OF core.

Drivers that want to handle multiple gpiochip instances from one
OF node need to implement a callback similar to this to
determine if a certain gpio chip is a pointer to the right
instance (pseudo-code):

struct my_gpio {
    struct gpio_chip gcs[MAX_CHIPS];
};

static bool my_of_node_instance_match(struct gpio_chip *gc
                                      unsigned int instance)
{
    struct my_gpio *mg = gpiochip_get_data(gc);

    if (instance >= MAX_CHIPS)
        return false;
    return (gc == &mg->gcs[instance]);
}

probe() {
    struct my_gpio *mg;
    struct gpio_chip *gc;
    int i, ret;

    for (i = 0; i++; i < MAX_CHIPS) {
        gc = &mg->gcs[i];
        /* This tells gpiolib we have several instances per node */
        gc->of_gpio_n_cells = 3;
	gc->of_node_instance_match = my_of_node_instance_match;
        gc->base = -1;
        ...

        ret = devm_gpiochip_add_data(dev, gc, mg);
        if (ret)
            return ret;
    }
}

Rename the "simple" of_xlate function to "twocell" which is closer
to what it actually does.

In the device tree bindings, the provide node needs
to specify #gpio-cells = <3>; where the first cell is the instance
number:

gpios = <&gpio instance offset flags>;

Conversely ranges need to have four cells:

gpio-ranges = <&pinctrl instance gpio_offset pin_offset count>;

Reviewed-by: Alex Elder <elder@riscstar.com>
Tested-by: Yixun Lan <dlan@gentoo.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20250225-gpio-ranges-fourcell-v3-2-860382ba4713@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
This commit is contained in:
Linus Walleij 2025-02-25 20:40:34 +01:00 committed by Bartosz Golaszewski
parent 732457dc46
commit bd3ce71078
2 changed files with 107 additions and 12 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

83
drivers/gpio/gpiolib-of.c
View file

@ -929,7 +929,7 @@ struct notifier_block gpio_of_notifier = {
#endif /* CONFIG_OF_DYNAMIC */
/**
* of_gpio_simple_xlate - translate gpiospec to the GPIO number and flags
* of_gpio_twocell_xlate - translate twocell gpiospec to the GPIO number and flags
* @gc: pointer to the gpio_chip structure
* @gpiospec: GPIO specifier as found in the device tree
* @flags: a flags pointer to fill in
@ -941,7 +941,7 @@ struct notifier_block gpio_of_notifier = {
* Returns:
* GPIO number (>= 0) on success, negative errno on failure.
*/
static int of_gpio_simple_xlate(struct gpio_chip *gc,
static int of_gpio_twocell_xlate(struct gpio_chip *gc,
const struct of_phandle_args *gpiospec,
u32 *flags)
{
@ -951,7 +951,7 @@ static int of_gpio_simple_xlate(struct gpio_chip *gc,
* number and the flags from a single gpio cell -- this is possible,
* but not recommended).
*/
if (gc->of_gpio_n_cells < 2) {
if (gc->of_gpio_n_cells != 2) {
WARN_ON(1);
return -EINVAL;
}
@ -968,6 +968,49 @@ static int of_gpio_simple_xlate(struct gpio_chip *gc,
return gpiospec->args[0];
}
/**
* of_gpio_threecell_xlate - translate threecell gpiospec to the GPIO number and flags
* @gc: pointer to the gpio_chip structure
* @gpiospec: GPIO specifier as found in the device tree
* @flags: a flags pointer to fill in
*
* This is simple translation function, suitable for the most 1:n mapped
* GPIO chips, i.e. several GPIO chip instances from one device tree node.
* In this case the following binding is implied:
*
* foo-gpios = <&gpio instance offset flags>;
*
* Returns:
* GPIO number (>= 0) on success, negative errno on failure.
*/
static int of_gpio_threecell_xlate(struct gpio_chip *gc,
const struct of_phandle_args *gpiospec,
u32 *flags)
{
if (gc->of_gpio_n_cells != 3) {
WARN_ON(1);
return -EINVAL;
}
if (WARN_ON(gpiospec->args_count != 3))
return -EINVAL;
/*
* Check chip instance number, the driver responds with true if
* this is the chip we are looking for.
*/
if (!gc->of_node_instance_match(gc, gpiospec->args[0]))
return -EINVAL;
if (gpiospec->args[1] >= gc->ngpio)
return -EINVAL;
if (flags)
*flags = gpiospec->args[2];
return gpiospec->args[1];
}
#if IS_ENABLED(CONFIG_OF_GPIO_MM_GPIOCHIP)
#include <linux/gpio/legacy-of-mm-gpiochip.h>
/**
@ -1068,7 +1111,15 @@ static int of_gpiochip_add_pin_range(struct gpio_chip *chip)
has_group_names = of_property_present(np, group_names_propname);
for (;; index++) {
ret = of_parse_phandle_with_fixed_args(np, "gpio-ranges", 3,
/*
* Ordinary phandles contain 2-3 cells:
* gpios = <&gpio [instance] offset flags>;
* Ranges always contain one more cell:
* gpio-ranges <&pinctrl [gpio_instance] gpio_offet pin_offet count>;
* This is why we parse chip->of_gpio_n_cells + 1 cells
*/
ret = of_parse_phandle_with_fixed_args(np, "gpio-ranges",
chip->of_gpio_n_cells + 1,
index, &pinspec);
if (ret)
break;
@ -1078,9 +1129,25 @@ static int of_gpiochip_add_pin_range(struct gpio_chip *chip)
if (!pctldev)
return -EPROBE_DEFER;
if (chip->of_gpio_n_cells == 3) {
/* First cell is the gpiochip instance number */
offset = pinspec.args[1];
pin = pinspec.args[2];
count = pinspec.args[3];
} else {
offset = pinspec.args[0];
pin = pinspec.args[1];
count = pinspec.args[2];
}
/*
* With multiple GPIO chips per node, check that this chip is the
* right instance.
*/
if (chip->of_node_instance_match &&
(chip->of_gpio_n_cells == 3) &&
!chip->of_node_instance_match(chip, pinspec.args[0]))
continue;
/* Ignore ranges outside of this GPIO chip */
if (offset >= (chip->offset + chip->ngpio))
@ -1170,8 +1237,14 @@ int of_gpiochip_add(struct gpio_chip *chip)
return 0;
if (!chip->of_xlate) {
if (chip->of_gpio_n_cells == 3) {
if (!chip->of_node_instance_match)
return -EINVAL;
chip->of_xlate = of_gpio_threecell_xlate;
} else {
chip->of_gpio_n_cells = 2;
chip->of_xlate = of_gpio_simple_xlate;
chip->of_xlate = of_gpio_twocell_xlate;
}
}
if (chip->of_gpio_n_cells > MAX_PHANDLE_ARGS)

24
include/linux/gpio/driver.h
View file

@ -531,10 +531,32 @@ struct gpio_chip {
/**
* @of_gpio_n_cells:
*
* Number of cells used to form the GPIO specifier.
* Number of cells used to form the GPIO specifier. The standard is 2
* cells:
*
* gpios = <&gpio offset flags>;
*
* some complex GPIO controllers instantiate more than one chip per
* device tree node and have 3 cells:
*
* gpios = <&gpio instance offset flags>;
*
* Legacy GPIO controllers may even have 1 cell:
*
* gpios = <&gpio offset>;
*/
unsigned int of_gpio_n_cells;
/**
* of_node_instance_match:
*
* Determine if a chip is the right instance. Must be implemented by
* any driver using more than one gpio_chip per device tree node.
* Returns true if gc is the instance indicated by i (which is the
* first cell in the phandles for GPIO lines and gpio-ranges).
*/
bool (*of_node_instance_match)(struct gpio_chip *gc, unsigned int i);
/**
* @of_xlate:
*