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![Vincent Whitchurch](/assets/img/avatar_default.png)
Hardware may require some time for the muxed analog signals to settle after the muxing is changed. Allow users of the mux subsystem to specify this delay with the new mux_control_select_delay() function (and the _try equivalent). Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> Reviewed-by: Lars-Peter Clausen <lars@metafoo.de> Tested-by: Lars-Peter Clausen <lars@metafoo.de> Acked-by: Peter Rosin <peda@axentia.se> Link: https://lore.kernel.org/r/20211007134641.13417-2-vincent.whitchurch@axis.com Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
567 lines
15 KiB
C
567 lines
15 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Multiplexer subsystem
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*
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* Copyright (C) 2017 Axentia Technologies AB
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*
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* Author: Peter Rosin <peda@axentia.se>
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*/
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#define pr_fmt(fmt) "mux-core: " fmt
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#include <linux/delay.h>
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#include <linux/device.h>
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#include <linux/err.h>
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#include <linux/export.h>
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#include <linux/idr.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/mux/consumer.h>
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#include <linux/mux/driver.h>
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#include <linux/of.h>
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#include <linux/of_platform.h>
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#include <linux/slab.h>
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/*
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* The idle-as-is "state" is not an actual state that may be selected, it
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* only implies that the state should not be changed. So, use that state
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* as indication that the cached state of the multiplexer is unknown.
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*/
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#define MUX_CACHE_UNKNOWN MUX_IDLE_AS_IS
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static struct class mux_class = {
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.name = "mux",
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.owner = THIS_MODULE,
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};
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static DEFINE_IDA(mux_ida);
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static int __init mux_init(void)
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{
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ida_init(&mux_ida);
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return class_register(&mux_class);
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}
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static void __exit mux_exit(void)
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{
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class_unregister(&mux_class);
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ida_destroy(&mux_ida);
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}
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static void mux_chip_release(struct device *dev)
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{
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struct mux_chip *mux_chip = to_mux_chip(dev);
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ida_simple_remove(&mux_ida, mux_chip->id);
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kfree(mux_chip);
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}
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static const struct device_type mux_type = {
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.name = "mux-chip",
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.release = mux_chip_release,
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};
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/**
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* mux_chip_alloc() - Allocate a mux-chip.
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* @dev: The parent device implementing the mux interface.
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* @controllers: The number of mux controllers to allocate for this chip.
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* @sizeof_priv: Size of extra memory area for private use by the caller.
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*
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* After allocating the mux-chip with the desired number of mux controllers
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* but before registering the chip, the mux driver is required to configure
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* the number of valid mux states in the mux_chip->mux[N].states members and
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* the desired idle state in the returned mux_chip->mux[N].idle_state members.
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* The default idle state is MUX_IDLE_AS_IS. The mux driver also needs to
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* provide a pointer to the operations struct in the mux_chip->ops member
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* before registering the mux-chip with mux_chip_register.
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*
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* Return: A pointer to the new mux-chip, or an ERR_PTR with a negative errno.
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*/
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struct mux_chip *mux_chip_alloc(struct device *dev,
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unsigned int controllers, size_t sizeof_priv)
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{
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struct mux_chip *mux_chip;
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int i;
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if (WARN_ON(!dev || !controllers))
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return ERR_PTR(-EINVAL);
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mux_chip = kzalloc(sizeof(*mux_chip) +
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controllers * sizeof(*mux_chip->mux) +
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sizeof_priv, GFP_KERNEL);
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if (!mux_chip)
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return ERR_PTR(-ENOMEM);
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mux_chip->mux = (struct mux_control *)(mux_chip + 1);
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mux_chip->dev.class = &mux_class;
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mux_chip->dev.type = &mux_type;
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mux_chip->dev.parent = dev;
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mux_chip->dev.of_node = dev->of_node;
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dev_set_drvdata(&mux_chip->dev, mux_chip);
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mux_chip->id = ida_simple_get(&mux_ida, 0, 0, GFP_KERNEL);
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if (mux_chip->id < 0) {
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int err = mux_chip->id;
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pr_err("muxchipX failed to get a device id\n");
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kfree(mux_chip);
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return ERR_PTR(err);
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}
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dev_set_name(&mux_chip->dev, "muxchip%d", mux_chip->id);
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mux_chip->controllers = controllers;
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for (i = 0; i < controllers; ++i) {
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struct mux_control *mux = &mux_chip->mux[i];
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mux->chip = mux_chip;
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sema_init(&mux->lock, 1);
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mux->cached_state = MUX_CACHE_UNKNOWN;
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mux->idle_state = MUX_IDLE_AS_IS;
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mux->last_change = ktime_get();
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}
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device_initialize(&mux_chip->dev);
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return mux_chip;
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}
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EXPORT_SYMBOL_GPL(mux_chip_alloc);
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static int mux_control_set(struct mux_control *mux, int state)
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{
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int ret = mux->chip->ops->set(mux, state);
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mux->cached_state = ret < 0 ? MUX_CACHE_UNKNOWN : state;
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if (ret >= 0)
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mux->last_change = ktime_get();
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return ret;
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}
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/**
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* mux_chip_register() - Register a mux-chip, thus readying the controllers
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* for use.
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* @mux_chip: The mux-chip to register.
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*
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* Do not retry registration of the same mux-chip on failure. You should
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* instead put it away with mux_chip_free() and allocate a new one, if you
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* for some reason would like to retry registration.
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*
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* Return: Zero on success or a negative errno on error.
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*/
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int mux_chip_register(struct mux_chip *mux_chip)
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{
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int i;
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int ret;
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for (i = 0; i < mux_chip->controllers; ++i) {
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struct mux_control *mux = &mux_chip->mux[i];
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if (mux->idle_state == mux->cached_state)
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continue;
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ret = mux_control_set(mux, mux->idle_state);
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if (ret < 0) {
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dev_err(&mux_chip->dev, "unable to set idle state\n");
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return ret;
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}
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}
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ret = device_add(&mux_chip->dev);
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if (ret < 0)
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dev_err(&mux_chip->dev,
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"device_add failed in %s: %d\n", __func__, ret);
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return ret;
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}
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EXPORT_SYMBOL_GPL(mux_chip_register);
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/**
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* mux_chip_unregister() - Take the mux-chip off-line.
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* @mux_chip: The mux-chip to unregister.
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*
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* mux_chip_unregister() reverses the effects of mux_chip_register().
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* But not completely, you should not try to call mux_chip_register()
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* on a mux-chip that has been registered before.
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*/
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void mux_chip_unregister(struct mux_chip *mux_chip)
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{
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device_del(&mux_chip->dev);
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}
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EXPORT_SYMBOL_GPL(mux_chip_unregister);
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/**
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* mux_chip_free() - Free the mux-chip for good.
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* @mux_chip: The mux-chip to free.
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*
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* mux_chip_free() reverses the effects of mux_chip_alloc().
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*/
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void mux_chip_free(struct mux_chip *mux_chip)
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{
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if (!mux_chip)
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return;
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put_device(&mux_chip->dev);
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}
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EXPORT_SYMBOL_GPL(mux_chip_free);
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static void devm_mux_chip_release(struct device *dev, void *res)
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{
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struct mux_chip *mux_chip = *(struct mux_chip **)res;
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mux_chip_free(mux_chip);
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}
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/**
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* devm_mux_chip_alloc() - Resource-managed version of mux_chip_alloc().
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* @dev: The parent device implementing the mux interface.
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* @controllers: The number of mux controllers to allocate for this chip.
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* @sizeof_priv: Size of extra memory area for private use by the caller.
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*
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* See mux_chip_alloc() for more details.
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*
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* Return: A pointer to the new mux-chip, or an ERR_PTR with a negative errno.
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*/
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struct mux_chip *devm_mux_chip_alloc(struct device *dev,
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unsigned int controllers,
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size_t sizeof_priv)
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{
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struct mux_chip **ptr, *mux_chip;
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ptr = devres_alloc(devm_mux_chip_release, sizeof(*ptr), GFP_KERNEL);
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if (!ptr)
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return ERR_PTR(-ENOMEM);
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mux_chip = mux_chip_alloc(dev, controllers, sizeof_priv);
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if (IS_ERR(mux_chip)) {
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devres_free(ptr);
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return mux_chip;
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}
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*ptr = mux_chip;
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devres_add(dev, ptr);
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return mux_chip;
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}
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EXPORT_SYMBOL_GPL(devm_mux_chip_alloc);
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static void devm_mux_chip_reg_release(struct device *dev, void *res)
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{
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struct mux_chip *mux_chip = *(struct mux_chip **)res;
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mux_chip_unregister(mux_chip);
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}
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/**
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* devm_mux_chip_register() - Resource-managed version mux_chip_register().
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* @dev: The parent device implementing the mux interface.
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* @mux_chip: The mux-chip to register.
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*
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* See mux_chip_register() for more details.
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*
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* Return: Zero on success or a negative errno on error.
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*/
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int devm_mux_chip_register(struct device *dev,
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struct mux_chip *mux_chip)
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{
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struct mux_chip **ptr;
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int res;
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ptr = devres_alloc(devm_mux_chip_reg_release, sizeof(*ptr), GFP_KERNEL);
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if (!ptr)
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return -ENOMEM;
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res = mux_chip_register(mux_chip);
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if (res) {
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devres_free(ptr);
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return res;
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}
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*ptr = mux_chip;
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devres_add(dev, ptr);
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return res;
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}
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EXPORT_SYMBOL_GPL(devm_mux_chip_register);
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/**
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* mux_control_states() - Query the number of multiplexer states.
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* @mux: The mux-control to query.
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*
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* Return: The number of multiplexer states.
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*/
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unsigned int mux_control_states(struct mux_control *mux)
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{
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return mux->states;
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}
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EXPORT_SYMBOL_GPL(mux_control_states);
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/*
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* The mux->lock must be down when calling this function.
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*/
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static int __mux_control_select(struct mux_control *mux, int state)
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{
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int ret;
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if (WARN_ON(state < 0 || state >= mux->states))
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return -EINVAL;
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if (mux->cached_state == state)
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return 0;
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ret = mux_control_set(mux, state);
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if (ret >= 0)
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return 0;
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/* The mux update failed, try to revert if appropriate... */
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if (mux->idle_state != MUX_IDLE_AS_IS)
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mux_control_set(mux, mux->idle_state);
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return ret;
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}
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static void mux_control_delay(struct mux_control *mux, unsigned int delay_us)
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{
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ktime_t delayend;
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s64 remaining;
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if (!delay_us)
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return;
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delayend = ktime_add_us(mux->last_change, delay_us);
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remaining = ktime_us_delta(delayend, ktime_get());
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if (remaining > 0)
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fsleep(remaining);
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}
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/**
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* mux_control_select_delay() - Select the given multiplexer state.
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* @mux: The mux-control to request a change of state from.
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* @state: The new requested state.
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* @delay_us: The time to delay (in microseconds) if the mux state is changed.
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*
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* On successfully selecting the mux-control state, it will be locked until
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* there is a call to mux_control_deselect(). If the mux-control is already
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* selected when mux_control_select() is called, the caller will be blocked
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* until mux_control_deselect() is called (by someone else).
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*
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* Therefore, make sure to call mux_control_deselect() when the operation is
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* complete and the mux-control is free for others to use, but do not call
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* mux_control_deselect() if mux_control_select() fails.
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*
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* Return: 0 when the mux-control state has the requested state or a negative
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* errno on error.
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*/
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int mux_control_select_delay(struct mux_control *mux, unsigned int state,
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unsigned int delay_us)
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{
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int ret;
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ret = down_killable(&mux->lock);
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if (ret < 0)
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return ret;
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ret = __mux_control_select(mux, state);
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if (ret >= 0)
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mux_control_delay(mux, delay_us);
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if (ret < 0)
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up(&mux->lock);
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return ret;
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}
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EXPORT_SYMBOL_GPL(mux_control_select_delay);
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/**
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* mux_control_try_select_delay() - Try to select the given multiplexer state.
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* @mux: The mux-control to request a change of state from.
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* @state: The new requested state.
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* @delay_us: The time to delay (in microseconds) if the mux state is changed.
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*
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* On successfully selecting the mux-control state, it will be locked until
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* mux_control_deselect() called.
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*
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* Therefore, make sure to call mux_control_deselect() when the operation is
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* complete and the mux-control is free for others to use, but do not call
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* mux_control_deselect() if mux_control_try_select() fails.
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*
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* Return: 0 when the mux-control state has the requested state or a negative
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* errno on error. Specifically -EBUSY if the mux-control is contended.
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*/
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int mux_control_try_select_delay(struct mux_control *mux, unsigned int state,
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unsigned int delay_us)
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{
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int ret;
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if (down_trylock(&mux->lock))
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return -EBUSY;
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ret = __mux_control_select(mux, state);
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if (ret >= 0)
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mux_control_delay(mux, delay_us);
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if (ret < 0)
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up(&mux->lock);
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return ret;
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}
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EXPORT_SYMBOL_GPL(mux_control_try_select_delay);
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/**
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* mux_control_deselect() - Deselect the previously selected multiplexer state.
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* @mux: The mux-control to deselect.
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*
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* It is required that a single call is made to mux_control_deselect() for
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* each and every successful call made to either of mux_control_select() or
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* mux_control_try_select().
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*
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* Return: 0 on success and a negative errno on error. An error can only
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* occur if the mux has an idle state. Note that even if an error occurs, the
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* mux-control is unlocked and is thus free for the next access.
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*/
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int mux_control_deselect(struct mux_control *mux)
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{
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int ret = 0;
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if (mux->idle_state != MUX_IDLE_AS_IS &&
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mux->idle_state != mux->cached_state)
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ret = mux_control_set(mux, mux->idle_state);
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up(&mux->lock);
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return ret;
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}
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EXPORT_SYMBOL_GPL(mux_control_deselect);
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/* Note this function returns a reference to the mux_chip dev. */
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static struct mux_chip *of_find_mux_chip_by_node(struct device_node *np)
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{
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struct device *dev;
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dev = class_find_device_by_of_node(&mux_class, np);
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return dev ? to_mux_chip(dev) : NULL;
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}
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/**
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* mux_control_get() - Get the mux-control for a device.
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* @dev: The device that needs a mux-control.
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* @mux_name: The name identifying the mux-control.
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*
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* Return: A pointer to the mux-control, or an ERR_PTR with a negative errno.
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*/
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struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
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{
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struct device_node *np = dev->of_node;
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struct of_phandle_args args;
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struct mux_chip *mux_chip;
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unsigned int controller;
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int index = 0;
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int ret;
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if (mux_name) {
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index = of_property_match_string(np, "mux-control-names",
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mux_name);
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if (index < 0) {
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dev_err(dev, "mux controller '%s' not found\n",
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mux_name);
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return ERR_PTR(index);
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}
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}
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ret = of_parse_phandle_with_args(np,
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"mux-controls", "#mux-control-cells",
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index, &args);
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if (ret) {
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dev_err(dev, "%pOF: failed to get mux-control %s(%i)\n",
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np, mux_name ?: "", index);
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return ERR_PTR(ret);
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}
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mux_chip = of_find_mux_chip_by_node(args.np);
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of_node_put(args.np);
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if (!mux_chip)
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return ERR_PTR(-EPROBE_DEFER);
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if (args.args_count > 1 ||
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(!args.args_count && (mux_chip->controllers > 1))) {
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dev_err(dev, "%pOF: wrong #mux-control-cells for %pOF\n",
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np, args.np);
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put_device(&mux_chip->dev);
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return ERR_PTR(-EINVAL);
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}
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controller = 0;
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if (args.args_count)
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controller = args.args[0];
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if (controller >= mux_chip->controllers) {
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dev_err(dev, "%pOF: bad mux controller %u specified in %pOF\n",
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np, controller, args.np);
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put_device(&mux_chip->dev);
|
|
return ERR_PTR(-EINVAL);
|
|
}
|
|
|
|
return &mux_chip->mux[controller];
|
|
}
|
|
EXPORT_SYMBOL_GPL(mux_control_get);
|
|
|
|
/**
|
|
* mux_control_put() - Put away the mux-control for good.
|
|
* @mux: The mux-control to put away.
|
|
*
|
|
* mux_control_put() reverses the effects of mux_control_get().
|
|
*/
|
|
void mux_control_put(struct mux_control *mux)
|
|
{
|
|
put_device(&mux->chip->dev);
|
|
}
|
|
EXPORT_SYMBOL_GPL(mux_control_put);
|
|
|
|
static void devm_mux_control_release(struct device *dev, void *res)
|
|
{
|
|
struct mux_control *mux = *(struct mux_control **)res;
|
|
|
|
mux_control_put(mux);
|
|
}
|
|
|
|
/**
|
|
* devm_mux_control_get() - Get the mux-control for a device, with resource
|
|
* management.
|
|
* @dev: The device that needs a mux-control.
|
|
* @mux_name: The name identifying the mux-control.
|
|
*
|
|
* Return: Pointer to the mux-control, or an ERR_PTR with a negative errno.
|
|
*/
|
|
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_release, 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);
|
|
|
|
/*
|
|
* Using subsys_initcall instead of module_init here to try to ensure - for
|
|
* the non-modular case - that the subsystem is initialized when mux consumers
|
|
* and mux controllers start to use it.
|
|
* For the modular case, the ordering is ensured with module dependencies.
|
|
*/
|
|
subsys_initcall(mux_init);
|
|
module_exit(mux_exit);
|
|
|
|
MODULE_DESCRIPTION("Multiplexer subsystem");
|
|
MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
|
|
MODULE_LICENSE("GPL v2");
|