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author | Charles Keepax <ckeepax@opensource.cirrus.com> | 2024-04-16 11:09:01 +0100 |
---|---|---|
committer | Mark Brown <broonie@kernel.org> | 2024-04-16 20:00:27 +0900 |
commit | 9d50f95bc0d5df56f2591b950a251d90bffad094 (patch) | |
tree | cca4352df9f3cc22969f5876decae4b1808e99fa /drivers | |
parent | fec50db7033ea478773b159e0e2efb135270e3b7 (diff) | |
download | linux-stable-9d50f95bc0d5df56f2591b950a251d90bffad094.tar.gz linux-stable-9d50f95bc0d5df56f2591b950a251d90bffad094.tar.bz2 linux-stable-9d50f95bc0d5df56f2591b950a251d90bffad094.zip |
gpio: swnode: Add ability to specify native chip selects for SPI
SPI devices can specify a cs-gpios property to enumerate their
chip selects. Under device tree, a zero entry in this property can
be used to specify that a particular chip select is using the SPI
controllers native chip select, for example:
cs-gpios = <&gpio1 0 0>, <0>;
Here, the second chip select is native. However, when using swnodes
there is currently no way to specify a native chip select. The
proposal here is to register a swnode_gpio_undefined software node,
that can be specified to allow the indication of a native chip
select. For example:
static const struct software_node_ref_args device_cs_refs[] = {
{
.node = &device_gpiochip_swnode,
.nargs = 2,
.args = { 0, GPIO_ACTIVE_LOW },
},
{
.node = &swnode_gpio_undefined,
.nargs = 0,
},
};
Register the swnode as the gpiolib is initialised and check in
swnode_get_gpio_device() if the returned node matches
swnode_gpio_undefined and return -ENOENT, which matches the
behaviour of the device tree system when it encounters a 0 phandle.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20240416100904.3738093-2-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/gpio/Kconfig | 9 | ||||
-rw-r--r-- | drivers/gpio/gpiolib-swnode.c | 44 |
2 files changed, 53 insertions, 0 deletions
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig index b50d0b470849..00b5c007a2bb 100644 --- a/drivers/gpio/Kconfig +++ b/drivers/gpio/Kconfig @@ -103,6 +103,15 @@ config GPIO_REGMAP select REGMAP tristate +config GPIO_SWNODE_UNDEFINED + bool + help + This adds a special place holder for software nodes to contain an + undefined GPIO reference, this is primarily used by SPI to allow a + list of GPIO chip selects to mark a certain chip select as being + controlled the SPI device's internal chip select mechanism and not + a GPIO. + # put drivers in the right section, in alphabetical order # This symbol is selected by both I2C and SPI expanders diff --git a/drivers/gpio/gpiolib-swnode.c b/drivers/gpio/gpiolib-swnode.c index fa52bdb1a29a..cec1ab878af8 100644 --- a/drivers/gpio/gpiolib-swnode.c +++ b/drivers/gpio/gpiolib-swnode.c @@ -4,8 +4,13 @@ * * Copyright 2022 Google LLC */ + +#define pr_fmt(fmt) "gpiolib: swnode: " fmt + #include <linux/err.h> #include <linux/errno.h> +#include <linux/export.h> +#include <linux/init.h> #include <linux/kernel.h> #include <linux/printk.h> #include <linux/property.h> @@ -17,6 +22,8 @@ #include "gpiolib.h" #include "gpiolib-swnode.h" +#define GPIOLIB_SWNODE_UNDEFINED_NAME "swnode-gpio-undefined" + static void swnode_format_propname(const char *con_id, char *propname, size_t max_size) { @@ -40,6 +47,14 @@ static struct gpio_device *swnode_get_gpio_device(struct fwnode_handle *fwnode) if (!gdev_node || !gdev_node->name) return ERR_PTR(-EINVAL); + /* + * Check for a special node that identifies undefined GPIOs, this is + * primarily used as a key for internal chip selects in SPI bindings. + */ + if (IS_ENABLED(CONFIG_GPIO_SWNODE_UNDEFINED) && + !strcmp(gdev_node->name, GPIOLIB_SWNODE_UNDEFINED_NAME)) + return ERR_PTR(-ENOENT); + gdev = gpio_device_find_by_label(gdev_node->name); return gdev ?: ERR_PTR(-EPROBE_DEFER); } @@ -121,3 +136,32 @@ int swnode_gpio_count(const struct fwnode_handle *fwnode, const char *con_id) return count ?: -ENOENT; } + +#if IS_ENABLED(CONFIG_GPIO_SWNODE_UNDEFINED) +/* + * A special node that identifies undefined GPIOs, this is primarily used as + * a key for internal chip selects in SPI bindings. + */ +const struct software_node swnode_gpio_undefined = { + .name = GPIOLIB_SWNODE_UNDEFINED_NAME, +}; +EXPORT_SYMBOL_NS_GPL(swnode_gpio_undefined, GPIO_SWNODE); + +static int __init swnode_gpio_init(void) +{ + int ret; + + ret = software_node_register(&swnode_gpio_undefined); + if (ret < 0) + pr_err("failed to register swnode: %d\n", ret); + + return ret; +} +subsys_initcall(swnode_gpio_init); + +static void __exit swnode_gpio_cleanup(void) +{ + software_node_unregister(&swnode_gpio_undefined); +} +__exitcall(swnode_gpio_cleanup); +#endif |