| Message ID | 20240415140925.3518990-2-ckeepax@opensource.cirrus.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Add bridged amplifiers to cs42l43 | expand |
On Mon, Apr 15, 2024 at 5:09 PM Charles Keepax <ckeepax@opensource.cirrus.com> wrote: > > 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. FWIW, Reviewed-by: Andy Shevchenko <andy@kernel.org> (I assume that this is _not_ going to be applied standalone as we don't want this without users, i.o.w. all or none as per this series)
On Mon, Apr 15, 2024 at 4:09 PM Charles Keepax <ckeepax@opensource.cirrus.com> wrote: > > 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> > Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com> > --- > Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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 diff --git a/include/linux/gpio/property.h b/include/linux/gpio/property.h index 6c75c8bd44a0..832a60c2e0b9 100644 --- a/include/linux/gpio/property.h +++ b/include/linux/gpio/property.h @@ -5,7 +5,11 @@ #include <dt-bindings/gpio/gpio.h> /* for GPIO_* flags */ #include <linux/property.h> +struct software_node; + #define PROPERTY_ENTRY_GPIO(_name_, _chip_node_, _idx_, _flags_) \ PROPERTY_ENTRY_REF(_name_, _chip_node_, _idx_, _flags_) +extern const struct software_node swnode_gpio_undefined; + #endif /* __LINUX_GPIO_PROPERTY_H */
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> Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com> --- Series changes since v5: - Add back help for GPIO_SWNODE_UNDEFINED - Correct some typos - Only check for undefined swnode if the Kconfig is set - Add a pr_fmt - Move swnode_gpio_undefined to include/linux/gpio/property.h Thanks, Charles drivers/gpio/Kconfig | 9 +++++++ drivers/gpio/gpiolib-swnode.c | 44 +++++++++++++++++++++++++++++++++++ include/linux/gpio/property.h | 4 ++++ 3 files changed, 57 insertions(+)