On 2016-11-19 16:34, Jonathan Cameron wrote: > On 17/11/16 21:48, Peter Rosin wrote: >> When both the iio subsystem and the i2c subsystem wants to update >> the same mux, there needs to be some coordination. Invent a new >> minimal "mux" subsystem that handles this. > I'd probably put something more general in the description. Lots of things > may need the same infrastructure. This is just an example. I'll make it more general for the next round. > Few bits inline. > > Also, I suspect you will fairly rapidly have a need for a strobe signal > as well. A lot of mux chips that are more than 2 way seem to have them to > allow multiple chips to be synchronized. I think that can be easily added later, when/if it's needed. >> >> Add a single backend driver for this new subsystem that can >> control gpio based multiplexers. >> --- >> drivers/misc/Kconfig | 6 + >> drivers/misc/Makefile | 2 + >> drivers/misc/mux-core.c | 299 ++++++++++++++++++++++++++++++++++++++++++++++++ >> drivers/misc/mux-gpio.c | 115 +++++++++++++++++++ >> include/linux/mux.h | 53 +++++++++ >> 5 files changed, 475 insertions(+) >> create mode 100644 drivers/misc/mux-core.c >> create mode 100644 drivers/misc/mux-gpio.c >> create mode 100644 include/linux/mux.h >> >> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig >> index 64971baf11fa..9e119bb78d82 100644 >> --- a/drivers/misc/Kconfig >> +++ b/drivers/misc/Kconfig >> @@ -766,6 +766,12 @@ config PANEL_BOOT_MESSAGE >> An empty message will only clear the display at driver init time. Any other >> printf()-formatted message is valid with newline and escape codes. >> >> +config MUX_GPIO >> + tristate "GPIO-controlled MUX controller" >> + depends on OF >> + help >> + GPIO-controlled MUX controller >> + >> source "drivers/misc/c2port/Kconfig" >> source "drivers/misc/eeprom/Kconfig" >> source "drivers/misc/cb710/Kconfig" >> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile >> index 31983366090a..92b547bcbac1 100644 >> --- a/drivers/misc/Makefile >> +++ b/drivers/misc/Makefile >> @@ -53,6 +53,8 @@ obj-$(CONFIG_ECHO) += echo/ >> obj-$(CONFIG_VEXPRESS_SYSCFG) += vexpress-syscfg.o >> obj-$(CONFIG_CXL_BASE) += cxl/ >> obj-$(CONFIG_PANEL) += panel.o >> +obj-$(CONFIG_MUX_GPIO) += mux-core.o >> +obj-$(CONFIG_MUX_GPIO) += mux-gpio.o >> >> lkdtm-$(CONFIG_LKDTM) += lkdtm_core.o >> lkdtm-$(CONFIG_LKDTM) += lkdtm_bugs.o >> diff --git a/drivers/misc/mux-core.c b/drivers/misc/mux-core.c >> new file mode 100644 >> index 000000000000..7a8bf003a92c >> --- /dev/null >> +++ b/drivers/misc/mux-core.c >> @@ -0,0 +1,299 @@ >> +/* >> + * Multiplexer subsystem >> + * >> + * Copyright (C) 2016 Axentia Technologies AB >> + * >> + * This program is free software; you can redistribute it and/or modify >> + * it under the terms of the GNU General Public License version 2 as >> + * published by the Free Software Foundation. >> + */ >> + >> +#define pr_fmt(fmt) "mux-core: " fmt >> + >> +#include <linux/device.h> >> +#include <linux/err.h> >> +#include <linux/idr.h> >> +#include <linux/module.h> >> +#include <linux/mux.h> >> +#include <linux/of.h> >> +#include <linux/slab.h> >> + >> +static struct bus_type mux_bus_type = { >> + .name = "mux", >> +}; >> + >> +static int __init mux_init(void) >> +{ >> + return bus_register(&mux_bus_type); >> +} >> + >> +static void __exit mux_exit(void) >> +{ >> + bus_unregister(&mux_bus_type); >> +} >> + >> +static DEFINE_IDA(mux_ida); >> + >> +static void mux_control_release(struct device *dev) >> +{ >> + struct mux_control *mux = to_mux_control(dev); >> + >> + ida_simple_remove(&mux_ida, mux->id); >> + kfree(mux); >> +} >> + >> +static struct device_type mux_control_type = { >> + .name = "mux-control", >> + .release = mux_control_release, >> +}; >> + >> +/* >> + * Allocate a mux-control, plus an extra memory area for private use >> + * by the caller. >> + */ >> +struct mux_control *mux_control_alloc(size_t sizeof_priv) >> +{ >> + struct mux_control *mux; >> + > Worth planning ahead for spi controlled muxes and others that need their > structures to be carefully aligned to avoid dma cacheline fun? > Easy enough to add later I guess. Right, I'll leave it for later when/if it's needed. >> + mux = kzalloc(sizeof(*mux) + sizeof_priv, GFP_KERNEL); >> + if (!mux) >> + return NULL; >> + >> + mux->dev.bus = &mux_bus_type; >> + mux->dev.type = &mux_control_type; >> + device_initialize(&mux->dev); >> + dev_set_drvdata(&mux->dev, mux); >> + >> + init_rwsem(&mux->lock); >> + mux->priv = mux + 1; > Needed? Or just do it with a bit of pointer math where the access is needed? Good suggestion, I'll add an inline function and drop the priv member. >> + >> + mux->id = ida_simple_get(&mux_ida, 0, 0, GFP_KERNEL); >> + if (mux->id < 0) { >> + pr_err("mux-controlX failed to get device id\n"); >> + kfree(mux); >> + return NULL; >> + } >> + dev_set_name(&mux->dev, "mux:control%d", mux->id); >> + >> + mux->cached_state = -1; >> + mux->idle_state = -1; >> + >> + return mux; >> +} >> +EXPORT_SYMBOL_GPL(mux_control_alloc); >> + >> +/* >> + * Register the mux-control, thus readying it for use. > Either single line comment style - or perhaps kernel doc the lot... Kernel doc was the plan from the start, coming up... >> + */ >> +int mux_control_register(struct mux_control *mux) >> +{ >> + /* If the calling driver did not initialize of_node, do it here */ >> + if (!mux->dev.of_node && mux->dev.parent) >> + mux->dev.of_node = mux->dev.parent->of_node; >> + >> + return device_add(&mux->dev); >> +} >> +EXPORT_SYMBOL_GPL(mux_control_register); >> + >> +/* >> + * Take the mux-control off-line. >> + */ >> +void mux_control_unregister(struct mux_control *mux) >> +{ >> + device_del(&mux->dev); >> +} >> +EXPORT_SYMBOL_GPL(mux_control_unregister); >> + >> +/* >> + * Put away the mux-control for good. >> + */ >> +void mux_control_put(struct mux_control *mux) >> +{ >> + if (!mux) >> + return; >> + put_device(&mux->dev); >> +} >> +EXPORT_SYMBOL_GPL(mux_control_put); >> + >> +static int mux_control_set(struct mux_control *mux, int state) >> +{ >> + int ret = mux->ops->set(mux, state); >> + >> + mux->cached_state = ret < 0 ? -1 : state; >> + >> + return ret; >> +} >> + >> +/* >> + * Select the given multiplexer channel. Call mux_control_deselect() >> + * when the operation is complete on the multiplexer channel, and the >> + * multiplexer is free for others to use. >> + */ >> +int mux_control_select(struct mux_control *mux, int state) >> +{ >> + int ret; >> + >> + if (down_read_trylock(&mux->lock)) { >> + if (mux->cached_state == state) >> + return 0; >> + >> + /* Sigh, the mux needs updating... */ >> + up_read(&mux->lock); >> + } >> + >> + /* ...or it's just contended. */ >> + down_write(&mux->lock); >> + >> + if (mux->cached_state == state) { >> + /* >> + * Hmmm, someone else changed the mux to my liking. >> + * That makes me wonder how long I waited for nothing... >> + */ >> + downgrade_write(&mux->lock); >> + return 0; >> + } >> + >> + ret = mux_control_set(mux, state); >> + if (ret < 0) { >> + if (mux->idle_state != -1) >> + mux_control_set(mux, mux->idle_state); >> + >> + up_write(&mux->lock); >> + return ret; >> + } >> + >> + downgrade_write(&mux->lock); >> + >> + return 1; >> +} >> +EXPORT_SYMBOL_GPL(mux_control_select); >> + >> +/* >> + * Deselect the previously selected multiplexer channel. >> + */ >> +int mux_control_deselect(struct mux_control *mux) >> +{ >> + int ret = 0; >> + >> + if (mux->idle_state != -1 && mux->cached_state != mux->idle_state) >> + ret = mux_control_set(mux, mux->idle_state); >> + >> + up_read(&mux->lock); >> + >> + return ret; >> +} >> +EXPORT_SYMBOL_GPL(mux_control_deselect); >> + >> +static int of_dev_node_match(struct device *dev, void *data) >> +{ >> + return dev->of_node == data; >> +} >> + >> +static struct mux_control *of_find_mux_by_node(struct device_node *np) >> +{ >> + struct device *dev; >> + >> + dev = bus_find_device(&mux_bus_type, NULL, np, of_dev_node_match); >> + >> + return dev ? to_mux_control(dev) : NULL; >> +} >> + >> +static struct mux_control *of_mux_control_get(struct device_node *np, int index) >> +{ >> + struct device_node *mux_np; >> + struct mux_control *mux; >> + >> + mux_np = of_parse_phandle(np, "control-muxes", index); >> + if (!mux_np) >> + return NULL; >> + >> + mux = of_find_mux_by_node(mux_np); >> + of_node_put(mux_np); >> + >> + return mux; >> +} >> + >> +/* >> + * Get a named mux. >> + */ >> +struct mux_control *mux_control_get(struct device *dev, const char *mux_name) >> +{ >> + struct device_node *np = dev->of_node; >> + struct mux_control *mux; >> + int index; >> + >> + index = of_property_match_string(np, "control-mux-names", mux_name); >> + if (index < 0) { >> + dev_err(dev, "failed to get control-mux %s:%s(%i)\n", >> + np->full_name, mux_name ?: "", index); >> + return ERR_PTR(index); >> + } >> + >> + mux = of_mux_control_get(np, index); >> + if (!mux) >> + return ERR_PTR(-EPROBE_DEFER); >> + >> + return mux; >> +} >> +EXPORT_SYMBOL_GPL(mux_control_get); >> + >> +static void devm_mux_control_free(struct device *dev, void *res) >> +{ >> + struct mux_control *mux = *(struct mux_control **)res; >> + >> + mux_control_put(mux); >> +} >> + >> +/* >> + * Get a named mux, with resource management. >> + */ > Guess it might be elsewhere in patch set but remember to add this to > the global list of devm interfaces (in Documentation somewhere.. IIRC) Right, now that you mention it, I remember having seen that document at some point. I'll look it up. Thanks for all comments! Cheers, Peter >> +struct mux_control *devm_mux_control_get(struct device *dev, >> + const char *mux_name) >> +{ >> + struct mux_control **ptr, *mux; >> + >> + ptr = devres_alloc(devm_mux_control_free, sizeof(*ptr), GFP_KERNEL); >> + if (!ptr) >> + return ERR_PTR(-ENOMEM); >> + >> + mux = mux_control_get(dev, mux_name); >> + if (IS_ERR(mux)) { >> + devres_free(ptr); >> + return mux; >> + } >> + >> + *ptr = mux; >> + devres_add(dev, ptr); >> + >> + return mux; >> +} >> +EXPORT_SYMBOL_GPL(devm_mux_control_get); >> + >> +static int devm_mux_control_match(struct device *dev, void *res, void *data) >> +{ >> + struct mux_control **r = res; >> + >> + if (!r || !*r) { >> + WARN_ON(!r || !*r); >> + return 0; >> + } >> + >> + return *r == data; >> +} >> + >> +/* >> + * Resource-managed version mux_control_put. >> + */ >> +void devm_mux_control_put(struct device *dev, struct mux_control *mux) >> +{ >> + WARN_ON(devres_release(dev, devm_mux_control_free, >> + devm_mux_control_match, mux)); >> +} >> +EXPORT_SYMBOL_GPL(devm_mux_control_put); >> + >> +subsys_initcall(mux_init); >> +module_exit(mux_exit); >> + >> +MODULE_AUTHOR("Peter Rosin <peda@xxxxxxxxxx"); >> +MODULE_DESCRIPTION("MUX subsystem"); >> +MODULE_LICENSE("GPL v2"); >> diff --git a/drivers/misc/mux-gpio.c b/drivers/misc/mux-gpio.c >> new file mode 100644 >> index 000000000000..2ddd7fb24078 >> --- /dev/null >> +++ b/drivers/misc/mux-gpio.c >> @@ -0,0 +1,115 @@ >> +/* >> + * GPIO-controlled multiplexer driver >> + * >> + * Copyright (C) 2016 Axentia Technologies AB >> + * >> + * This program is free software; you can redistribute it and/or modify >> + * it under the terms of the GNU General Public License version 2 as >> + * published by the Free Software Foundation. >> + */ >> + >> +#include <linux/err.h> >> +#include <linux/gpio/consumer.h> >> +#include <linux/module.h> >> +#include <linux/mux.h> >> +#include <linux/of.h> >> +#include <linux/of_platform.h> >> +#include <linux/platform_device.h> >> + >> +struct mux_gpio { >> + struct gpio_descs *gpios; >> +}; >> + >> +static int mux_gpio_set(struct mux_control *mux, int val) >> +{ >> + struct mux_gpio *mux_gpio = mux->priv; >> + int i; >> + >> + for (i = 0; i < mux_gpio->gpios->ndescs; i++) >> + gpiod_set_value_cansleep(mux_gpio->gpios->desc[i], >> + val & (1 << i)); >> + >> + return 0; >> +} >> + >> +static const struct mux_control_ops mux_gpio_ops = { >> + .set = mux_gpio_set, >> +}; >> + >> +static const struct of_device_id mux_gpio_dt_ids[] = { >> + { .compatible = "mux-gpio", }, >> + { /* sentinel */ } >> +}; >> +MODULE_DEVICE_TABLE(of, mux_gpio_dt_ids); >> + >> +static int mux_gpio_probe(struct platform_device *pdev) >> +{ >> + struct device *dev = &pdev->dev; >> + struct device_node *np = pdev->dev.of_node; >> + struct mux_control *mux; >> + struct mux_gpio *mux_gpio; >> + u32 idle_state; >> + int ret; >> + >> + if (!np) >> + return -ENODEV; >> + >> + mux = mux_control_alloc(sizeof(*mux_gpio)); >> + if (!mux) >> + return -ENOMEM; >> + mux_gpio = mux->priv; >> + mux->dev.parent = dev; >> + mux->ops = &mux_gpio_ops; >> + >> + platform_set_drvdata(pdev, mux); >> + >> + mux_gpio->gpios = devm_gpiod_get_array(dev, "mux", GPIOD_OUT_LOW); >> + if (IS_ERR(mux_gpio->gpios)) { >> + if (PTR_ERR(mux_gpio->gpios) != -EPROBE_DEFER) >> + dev_err(dev, "failed to get gpios\n"); >> + mux_control_put(mux); >> + return PTR_ERR(mux_gpio->gpios); >> + } >> + >> + ret = of_property_read_u32(np, "idle-state", &idle_state); >> + if (ret >= 0) { >> + if (idle_state >= (1 << mux_gpio->gpios->ndescs)) { >> + dev_err(dev, "invalid idle-state %u\n", idle_state); >> + return -EINVAL; >> + } >> + mux->idle_state = idle_state; >> + } >> + >> + ret = mux_control_register(mux); >> + if (ret < 0) { >> + dev_err(dev, "failed to register mux_control\n"); >> + mux_control_put(mux); >> + return ret; >> + } >> + >> + return ret; >> +} >> + >> +static int mux_gpio_remove(struct platform_device *pdev) >> +{ >> + struct device *dev = &pdev->dev; >> + struct mux_control *mux = to_mux_control(dev); >> + >> + mux_control_unregister(mux); >> + mux_control_put(mux); >> + return 0; >> +} >> + >> +static struct platform_driver mux_gpio_driver = { >> + .driver = { >> + .name = "mux-gpio", >> + .of_match_table = of_match_ptr(mux_gpio_dt_ids), >> + }, >> + .probe = mux_gpio_probe, >> + .remove = mux_gpio_remove, >> +}; >> +module_platform_driver(mux_gpio_driver); >> + >> +MODULE_AUTHOR("Peter Rosin <peda@xxxxxxxxxx"); >> +MODULE_DESCRIPTION("GPIO-controlled multiplexer driver"); >> +MODULE_LICENSE("GPL v2"); >> diff --git a/include/linux/mux.h b/include/linux/mux.h >> new file mode 100644 >> index 000000000000..5b21b8184056 >> --- /dev/null >> +++ b/include/linux/mux.h >> @@ -0,0 +1,53 @@ >> +/* >> + * mux.h - definitions for the multiplexer interface >> + * >> + * Copyright (C) 2016 Axentia Technologies AB >> + * >> + * This program is free software; you can redistribute it and/or modify >> + * it under the terms of the GNU General Public License version 2 as >> + * published by the Free Software Foundation. >> + */ >> + >> +#ifndef _LINUX_MUX_H >> +#define _LINUX_MUX_H >> + >> +#include <linux/device.h> >> +#include <linux/rwsem.h> >> + >> +struct mux_control; >> + >> +struct mux_control_ops { >> + int (*set)(struct mux_control *mux, int reg); >> +}; >> + >> +struct mux_control { >> + struct rw_semaphore lock; /* protects the state of the mux */ >> + >> + struct device dev; >> + int id; >> + >> + int cached_state; >> + int idle_state; >> + >> + const struct mux_control_ops *ops; >> + >> + void *priv; >> +}; >> + >> +#define to_mux_control(x) container_of((x), struct mux_control, dev) >> + >> +struct mux_control *mux_control_alloc(size_t sizeof_priv); >> +int mux_control_register(struct mux_control *mux); >> +void mux_control_unregister(struct mux_control *mux); >> +void mux_control_put(struct mux_control *mux); >> + >> +int mux_control_select(struct mux_control *mux, int state); >> +int mux_control_deselect(struct mux_control *mux); >> + >> +struct mux_control *mux_control_get(struct device *dev, >> + const char *mux_name); >> +struct mux_control *devm_mux_control_get(struct device *dev, >> + const char *mux_name); >> +void devm_mux_control_put(struct device *dev, struct mux_control *mux); >> + >> +#endif /* _LINUX_MUX_H */ >> > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html