drivers: Add a new framework for multiplexer devices

Add a new subsystem that handles multiplexer controllers. The API is the
same as in Linux.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
[trini: Update some error calls to use different functions or pass
        correct arguments]
Signed-off-by: Tom Rini <trini@konsulko.com>

9 files changed, 606 insertions, 0 deletions

diff --git a/drivers/Kconfig b/drivers/Kconfig
index 613669c..ed8a39c 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -64,6 +64,8 @@ source "drivers/mmc/Kconfig"
 
 source "drivers/mtd/Kconfig"
 
+source "drivers/mux/Kconfig"
+
 source "drivers/net/Kconfig"
 
 source "drivers/nvme/Kconfig"
diff --git a/drivers/Makefile b/drivers/Makefile
index 9eb5145..33f1d53 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -14,6 +14,7 @@ obj-$(CONFIG_$(SPL_TPL_)INPUT) += input/
 obj-$(CONFIG_$(SPL_TPL_)LED) += led/
 obj-$(CONFIG_$(SPL_TPL_)MMC_SUPPORT) += mmc/
 obj-y += mtd/
+obj-$(CONFIG_$(SPL_)MULTIPLEXER) += mux/
 obj-$(CONFIG_$(SPL_TPL_)PCH_SUPPORT) += pch/
 obj-$(CONFIG_$(SPL_TPL_)PCI) += pci/
 obj-$(CONFIG_$(SPL_TPL_)PHY) += phy/
diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
new file mode 100644
index 0000000..35c1c56
--- /dev/null
+++ b/drivers/mux/Kconfig
@@ -0,0 +1,11 @@
+menu "Multiplexer drivers"
+
+config MULTIPLEXER
+	bool "Multiplexer Support"
+	depends on DM
+	help
+	 The mux framework is a minimalistic subsystem that handles multiplexer
+	 controllers. It provides the same API as Linux and mux drivers should
+	 be portable with a minimum effort.
+
+endmenu
diff --git a/drivers/mux/Makefile b/drivers/mux/Makefile
new file mode 100644
index 0000000..351e436
--- /dev/null
+++ b/drivers/mux/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# (C) Copyright 2019
+# Jean-Jacques Hiblot <jjhiblot@ti.com>
+
+obj-$(CONFIG_$(SPL_)MULTIPLEXER) += mux-uclass.o
diff --git a/drivers/mux/mux-uclass.c b/drivers/mux/mux-uclass.c
new file mode 100644
index 0000000..815df93
--- /dev/null
+++ b/drivers/mux/mux-uclass.c
@@ -0,0 +1,312 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Multiplexer subsystem
+ *
+ * Based on the linux multiplexer framework
+ *
+ * Copyright (C) 2017 Axentia Technologies AB
+ * Author: Peter Rosin <peda@axentia.se>
+ *
+ * Copyright (C) 2017-2018 Texas Instruments Incorporated - http://www.ti.com/
+ * Jean-Jacques Hiblot <jjhiblot@ti.com>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <mux-internal.h>
+#include <dm/device-internal.h>
+#include <dm/device_compat.h>
+#include <dm/devres.h>
+#include <dt-bindings/mux/mux.h>
+#include <linux/bug.h>
+
+/*
+ * The idle-as-is "state" is not an actual state that may be selected, it
+ * only implies that the state should not be changed. So, use that state
+ * as indication that the cached state of the multiplexer is unknown.
+ */
+#define MUX_CACHE_UNKNOWN MUX_IDLE_AS_IS
+
+/**
+ * mux_control_ops() - Get the mux_control ops.
+ * @dev: The client device.
+ *
+ * Return: A pointer to the 'mux_control_ops' of the device.
+ */
+static inline const struct mux_control_ops *mux_dev_ops(struct udevice *dev)
+{
+	return (const struct mux_control_ops *)dev->driver->ops;
+}
+
+/**
+ * mux_control_set() - Set the state of the given mux controller.
+ * @mux: A multiplexer control
+ * @state: The new requested state.
+ *
+ * Return: 0 if OK, or a negative error code.
+ */
+static int mux_control_set(struct mux_control *mux, int state)
+{
+	int ret = mux_dev_ops(mux->dev)->set(mux, state);
+
+	mux->cached_state = ret < 0 ? MUX_CACHE_UNKNOWN : state;
+
+	return ret;
+}
+
+unsigned int mux_control_states(struct mux_control *mux)
+{
+	return mux->states;
+}
+
+/**
+ * __mux_control_select() - Select the given multiplexer state.
+ * @mux: The mux-control to request a change of state from.
+ * @state: The new requested state.
+ *
+ * Try to set the mux to the requested state. If not, try to revert if
+ * appropriate.
+ */
+static int __mux_control_select(struct mux_control *mux, int state)
+{
+	int ret;
+
+	if (WARN_ON(state < 0 || state >= mux->states))
+		return -EINVAL;
+
+	if (mux->cached_state == state)
+		return 0;
+
+	ret = mux_control_set(mux, state);
+	if (ret >= 0)
+		return 0;
+
+	/* The mux update failed, try to revert if appropriate... */
+	if (mux->idle_state != MUX_IDLE_AS_IS)
+		mux_control_set(mux, mux->idle_state);
+
+	return ret;
+}
+
+int mux_control_select(struct mux_control *mux, unsigned int state)
+{
+	int ret;
+
+	if (mux->in_use)
+		return -EBUSY;
+
+	ret = __mux_control_select(mux, state);
+
+	if (ret < 0)
+		return ret;
+
+	mux->in_use = true;
+
+	return 0;
+}
+
+int mux_control_deselect(struct mux_control *mux)
+{
+	int ret = 0;
+
+	if (mux->idle_state != MUX_IDLE_AS_IS &&
+	    mux->idle_state != mux->cached_state)
+		ret = mux_control_set(mux, mux->idle_state);
+
+	mux->in_use = false;
+
+	return ret;
+}
+
+static int mux_of_xlate_default(struct mux_chip *mux_chip,
+				struct ofnode_phandle_args *args,
+				struct mux_control **muxp)
+{
+	struct mux_control *mux;
+	int id;
+
+	log_debug("%s(muxp=%p)\n", __func__, muxp);
+
+	if (args->args_count > 1) {
+		debug("Invaild args_count: %d\n", args->args_count);
+		return -EINVAL;
+	}
+
+	if (args->args_count)
+		id = args->args[0];
+	else
+		id = 0;
+
+	if (id >= mux_chip->controllers) {
+		pr_err("bad mux controller %u specified in %s\n",
+			id, ofnode_get_name(args->node));
+		return -ERANGE;
+	}
+
+	mux = &mux_chip->mux[id];
+	mux->id = id;
+	*muxp = mux;
+	return 0;
+}
+
+/**
+ * mux_get_by_indexed_prop() - Get a mux control by integer index
+ * @dev: The client device.
+ * @prop_name: Name of the device tree property.
+ * @index: The index of the mux to get
+ * @mux: A pointer to the 'mux_control' struct to initialize.
+ *
+ * Return: 0 of OK, -errno otherwise.
+ */
+static int mux_get_by_indexed_prop(struct udevice *dev, const char *prop_name,
+				   int index, struct mux_control **mux)
+{
+	int ret;
+	struct ofnode_phandle_args args;
+	struct udevice *dev_mux;
+	const struct mux_control_ops *ops;
+	struct mux_chip *mux_chip;
+
+	log_debug("%s(dev=%p, index=%d, mux=%p)\n", __func__, dev, index, mux);
+
+	ret = dev_read_phandle_with_args(dev, prop_name, "#mux-control-cells",
+					 0, index, &args);
+	if (ret) {
+		debug("%s: fdtdec_parse_phandle_with_args failed: err=%d\n",
+		      __func__, ret);
+		return ret;
+	}
+
+	ret = uclass_get_device_by_ofnode(UCLASS_MUX, args.node, &dev_mux);
+	if (ret) {
+		debug("%s: uclass_get_device_by_ofnode failed: err=%d\n",
+		      __func__, ret);
+		return ret;
+	}
+
+	mux_chip = dev_get_uclass_priv(dev_mux);
+
+	ops = mux_dev_ops(dev_mux);
+	if (ops->of_xlate)
+		ret = ops->of_xlate(mux_chip, &args, mux);
+	else
+		ret = mux_of_xlate_default(mux_chip, &args, mux);
+	if (ret) {
+		debug("of_xlate() failed: %d\n", ret);
+		return ret;
+	}
+	(*mux)->dev = dev_mux;
+
+	return 0;
+}
+
+int mux_get_by_index(struct udevice *dev, int index, struct mux_control **mux)
+{
+	return mux_get_by_indexed_prop(dev, "mux-controls", index, mux);
+}
+
+int mux_control_get(struct udevice *dev, const char *name,
+		    struct mux_control **mux)
+{
+	int index;
+
+	debug("%s(dev=%p, name=%s, mux=%p)\n", __func__, dev, name, mux);
+
+	index = dev_read_stringlist_search(dev, "mux-control-names", name);
+	if (index < 0) {
+		debug("fdt_stringlist_search() failed: %d\n", index);
+		return index;
+	}
+
+	return mux_get_by_index(dev, index, mux);
+}
+
+void mux_control_put(struct mux_control *mux)
+{
+	mux_control_deselect(mux);
+}
+
+/**
+ * devm_mux_control_release() - Release the given managed mux.
+ * @dev: The client device.
+ * @res: Pointer to the mux to be released.
+ *
+ * This function is called by devres to release the mux. It reverses the
+ * effects of mux_control_get().
+ */
+static void devm_mux_control_release(struct udevice *dev, void *res)
+{
+	mux_control_put(*(struct mux_control **)res);
+}
+
+struct mux_control *devm_mux_control_get(struct udevice *dev, const char *id)
+{
+	int rc;
+	struct mux_control **mux;
+
+	mux = devres_alloc(devm_mux_control_release,
+			   sizeof(struct mux_control *), __GFP_ZERO);
+	if (unlikely(!mux))
+		return ERR_PTR(-ENOMEM);
+
+	rc = mux_control_get(dev, id, mux);
+	if (rc)
+		return ERR_PTR(rc);
+
+	devres_add(dev, mux);
+	return *mux;
+}
+
+int mux_alloc_controllers(struct udevice *dev, unsigned int controllers)
+{
+	int i;
+	struct mux_chip *mux_chip = dev_get_uclass_priv(dev);
+
+	mux_chip->mux = devm_kmalloc(dev,
+				     sizeof(struct mux_control) * controllers,
+				     __GFP_ZERO);
+	if (!mux_chip->mux)
+		return -ENOMEM;
+
+	mux_chip->controllers = controllers;
+
+	for (i = 0; i < mux_chip->controllers; ++i) {
+		struct mux_control *mux = &mux_chip->mux[i];
+
+		mux->dev = dev;
+		mux->cached_state = MUX_CACHE_UNKNOWN;
+		mux->idle_state = MUX_IDLE_AS_IS;
+		mux->in_use = false;
+		mux->id = i;
+	}
+
+	return 0;
+}
+
+static int mux_uclass_post_probe(struct udevice *dev)
+{
+	int i, ret;
+	struct mux_chip *mux_chip = dev_get_uclass_priv(dev);
+
+	/* Set all mux controllers to their idle state. */
+	for (i = 0; i < mux_chip->controllers; ++i) {
+		struct mux_control *mux = &mux_chip->mux[i];
+
+		if (mux->idle_state == mux->cached_state)
+			continue;
+
+		ret = mux_control_set(mux, mux->idle_state);
+		if (ret < 0) {
+			dev_err(dev, "unable to set idle state\n");
+			return ret;
+		}
+	}
+	return 0;
+}
+
+UCLASS_DRIVER(mux) = {
+	.id		= UCLASS_MUX,
+	.name		= "mux",
+	.post_probe	= mux_uclass_post_probe,
+	.per_device_auto_alloc_size = sizeof(struct mux_chip),
+};
diff --git a/include/dm/uclass-id.h b/include/dm/uclass-id.h
index 88f10c4..17542de 100644
--- a/include/dm/uclass-id.h
+++ b/include/dm/uclass-id.h
@@ -71,6 +71,7 @@ enum uclass_id {
 	UCLASS_MMC,		/* SD / MMC card or chip */
 	UCLASS_MOD_EXP,		/* RSA Mod Exp device */
 	UCLASS_MTD,		/* Memory Technology Device (MTD) device */
+	UCLASS_MUX,		/* Multiplexer device */
 	UCLASS_NOP,		/* No-op devices */
 	UCLASS_NORTHBRIDGE,	/* Intel Northbridge / SDRAM controller */
 	UCLASS_NVME,		/* NVM Express device */
diff --git a/include/dt-bindings/mux/mux.h b/include/dt-bindings/mux/mux.h
new file mode 100644
index 0000000..0427192
--- /dev/null
+++ b/include/dt-bindings/mux/mux.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * This header provides constants for most Multiplexer bindings.
+ *
+ * Most Multiplexer bindings specify an idle state. In most cases, the
+ * the multiplexer can be left as is when idle, and in some cases it can
+ * disconnect the input/output and leave the multiplexer in a high
+ * impedance state.
+ */
+
+#ifndef _DT_BINDINGS_MUX_MUX_H
+#define _DT_BINDINGS_MUX_MUX_H
+
+#define MUX_IDLE_AS_IS      (-1)
+#define MUX_IDLE_DISCONNECT (-2)
+
+#endif
diff --git a/include/mux-internal.h b/include/mux-internal.h
new file mode 100644
index 0000000..93e3a5c
--- /dev/null
+++ b/include/mux-internal.h
@@ -0,0 +1,109 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Based on the linux multiplexer framework
+ *
+ * Copyright (C) 2017 Axentia Technologies AB
+ * Author: Peter Rosin <peda@axentia.se>
+ *
+ * Copyright (C) 2017-2018 Texas Instruments Incorporated - http://www.ti.com/
+ * Jean-Jacques Hiblot <jjhiblot@ti.com>
+ */
+
+#ifndef _MUX_INTERNAL_H
+#define _MUX_INTERNAL_H
+
+/* See mux.h for background documentation. */
+
+struct ofnode_phandle_args;
+
+/**
+ * struct mux_chip -	Represents a chip holding mux controllers.
+ * @controllers:	Number of mux controllers handled by the chip.
+ * @mux:		Array of mux controllers that are handled.
+ *
+ * This a per-device uclass-private data.
+ */
+struct mux_chip {
+	unsigned int controllers;
+	struct mux_control *mux;
+};
+
+/**
+ * struct mux_control_ops -	Mux controller operations for a mux chip.
+ * @set:			Set the state of the given mux controller.
+ */
+struct mux_control_ops {
+	/**
+	 * set - Apply a state to a multiplexer control
+	 *
+	 * @mux:	A multiplexer control
+	 * @return 0 if OK, or a negative error code.
+	 */
+	int (*set)(struct mux_control *mux, int state);
+
+	/**
+	 * of_xlate - Translate a client's device-tree (OF) multiplexer
+	 * specifier.
+	 *
+	 * If this function pointer is set to NULL, the multiplexer core will
+	 * use a default implementation, which assumes #mux-control-cells = <1>
+	 * and that the DT cell contains a simple integer channel ID.
+	 *
+	 * @dev_mux:	The multiplexer device. A single device may handle
+	 *              several multiplexer controls.
+	 * @args:	The multiplexer specifier values from device tree.
+	 * @muxp:	(out) A multiplexer control
+	 * @return 0 if OK, or a negative error code.
+	 */
+	int (*of_xlate)(struct mux_chip *dev_mux,
+			struct ofnode_phandle_args *args,
+			struct mux_control **muxp);
+};
+
+/**
+ * struct mux_control -	Represents a mux controller.
+ * @in_use:		Whether the mux controller is in use or not.
+ * @dev:		The client device.
+ * @cached_state:	The current mux controller state, or -1 if none.
+ * @states:		The number of mux controller states.
+ * @idle_state:		The mux controller state to use when inactive, or one
+ *			of MUX_IDLE_AS_IS and MUX_IDLE_DISCONNECT.
+ * @id:			The index of the mux controller within the mux chip
+ *			it is a part of.
+ *
+ * Mux drivers may only change @states and @idle_state, and may only do so
+ * between allocation and registration of the mux controller. Specifically,
+ * @cached_state is internal to the mux core and should never be written by
+ * mux drivers.
+ */
+struct mux_control {
+	bool	in_use;
+	struct udevice *dev;
+	int cached_state;
+	unsigned int states;
+	int idle_state;
+	int id;
+};
+
+/**
+ * mux_control_get_index() - Get the index of the given mux controller
+ * @mux:		The mux-control to get the index for.
+ *
+ * Return: The index of the mux controller within the mux chip the mux
+ * controller is a part of.
+ */
+static inline unsigned int mux_control_get_index(struct mux_control *mux)
+{
+	return mux->id;
+}
+
+/**
+ * mux_alloc_controllers() - Allocate the given number of mux controllers.
+ * @dev:		The client device.
+ * controllers:		Number of controllers to allocate.
+ *
+ * Return: 0 of OK, -errno otherwise.
+ */
+int mux_alloc_controllers(struct udevice *dev, unsigned int controllers);
+
+#endif
diff --git a/include/mux.h b/include/mux.h
new file mode 100644
index 0000000..85eb7d4
--- /dev/null
+++ b/include/mux.h
@@ -0,0 +1,147 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Based on the linux multiplexer framework
+ *
+ * At its core, a multiplexer (or mux), also known as a data selector, is a
+ * device that selects between several analog or digital input signals and
+ * forwards it to a single output line. This notion can be extended to work
+ * with buses, like a I2C bus multiplexer for example.
+ *
+ * Copyright (C) 2017 Axentia Technologies AB
+ * Author: Peter Rosin <peda@axentia.se>
+ *
+ * Copyright (C) 2017-2018 Texas Instruments Incorporated - http://www.ti.com/
+ * Jean-Jacques Hiblot <jjhiblot@ti.com>
+ */
+
+#ifndef _MUX_H_
+#define _MUX_H_
+
+#include <linux/errno.h>
+#include <linux/types.h>
+
+struct udevice;
+struct mux_control;
+
+#if CONFIG_IS_ENABLED(MULTIPLEXER)
+/**
+ * mux_control_states() - Query the number of multiplexer states.
+ * @mux: The mux-control to query.
+ *
+ * Return: The number of multiplexer states.
+ */
+unsigned int mux_control_states(struct mux_control *mux);
+
+/**
+ * mux_control_select() - Select the given multiplexer state.
+ * @mux: The mux-control to request a change of state from.
+ * @state: The new requested state.
+ *
+ * On successfully selecting the mux-control state, it will be locked until
+ * there is a call to mux_control_deselect(). If the mux-control is already
+ * selected when mux_control_select() is called, the function will indicate
+ * -EBUSY
+ *
+ * Therefore, make sure to call mux_control_deselect() when the operation is
+ * complete and the mux-control is free for others to use, but do not call
+ * mux_control_deselect() if mux_control_select() fails.
+ *
+ * Return: 0 when the mux-control state has the requested state or a negative
+ * errno on error.
+ */
+int __must_check mux_control_select(struct mux_control *mux,
+				    unsigned int state);
+#define mux_control_try_select(mux) mux_control_select(mux)
+
+/**
+ * mux_control_deselect() - Deselect the previously selected multiplexer state.
+ * @mux: The mux-control to deselect.
+ *
+ * It is required that a single call is made to mux_control_deselect() for
+ * each and every successful call made to either of mux_control_select() or
+ * mux_control_try_select().
+ *
+ * Return: 0 on success and a negative errno on error. An error can only
+ * occur if the mux has an idle state. Note that even if an error occurs, the
+ * mux-control is unlocked and is thus free for the next access.
+ */
+int mux_control_deselect(struct mux_control *mux);
+
+/**
+ * mux_get_by_index() = Get a mux by integer index.
+ * @dev: The client device.
+ * @index: The index of the mux to get.
+ * @mux: A pointer to the 'mux_control' struct to initialize.
+ *
+ * This looks up and initializes a mux. The index is relative to the client
+ * device.
+ *
+ * Return: 0 if OK, or a negative error code.
+ */
+int mux_get_by_index(struct udevice *dev, int index, struct mux_control **mux);
+
+/**
+ * mux_control_get() - Get the mux-control for a device.
+ * @dev: The device that needs a mux-control.
+ * @mux_name: The name identifying the mux-control.
+ * @mux: A pointer to the mux-control pointer.
+ *
+ * Return: 0 of OK, or a negative error code.
+ */
+int mux_control_get(struct udevice *dev, const char *name,
+		    struct mux_control **mux);
+
+/**
+ * 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);
+
+/**
+ * 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 udevice *dev,
+					 const char *mux_name);
+#else
+unsigned int mux_control_states(struct mux_control *mux)
+{
+	return -ENOSYS;
+}
+
+int __must_check mux_control_select(struct mux_control *mux,
+				    unsigned int state)
+{
+	return -ENOSYS;
+}
+
+#define mux_control_try_select(mux) mux_control_select(mux)
+
+int mux_control_deselect(struct mux_control *mux)
+{
+	return -ENOSYS;
+}
+
+struct mux_control *mux_control_get(struct udevice *dev, const char *mux_name)
+{
+	return NULL;
+}
+
+void mux_control_put(struct mux_control *mux)
+{
+}
+
+struct mux_control *devm_mux_control_get(struct udevice *dev,
+					 const char *mux_name)
+{
+	return NULL;
+}
+#endif
+
+#endif