[PATCH mfd+gpio 1/2] drivers: mfd: Add support for Moxtet bus

[PATCH mfd+gpio 1/2] drivers: mfd: Add support for Moxtet bus

[Marek Behún]

On the Turris Mox router there can be connected different modules to
the main CPU board, currently a module with a SFP cage, a module with
MiniPCIe connector, a 4-port switch module and a 8-port switch module,
for example:
  [CPU]-[PCIe]-[8-port switch]-[8-port switch]-[SFP]

Each of this modules has an input and output shift register, and these
are connected via SPI to CPU board.

Via this SPI connection we are able to discover which modules are
connected and we can also read/write some configuration to the modules.
Fromi/to each module 8 bits can be read (of which lower 4 bits identify
the module) and written.

For example from the module with a SFP cage we can read the LOS,
TX-FAULT and MOD-DEF0 signals, while we can write TX-DISABLE and
RATE-SELECT signals.

Other modules may support something else.

This driver creates a new bus type, called "moxtet". For each Mox module
it finds via SPI, it creates a new device on the moxtet bus so that
drivers can be written for them, for example a gpio driver for the
module with a SFP cage.

The topology of how Mox modules are connected can then be read by
listing /sys/bus/moxtet/devices.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
---
 Documentation/devicetree/bindings/mfd/moxtet.txt |  36 ++
 MAINTAINERS                                      |   7 +
 drivers/mfd/Kconfig                              |  10 +
 drivers/mfd/Makefile                             |   1 +
 drivers/mfd/moxtet.c                             | 501 +++++++++++++++++++++++
 include/linux/mfd/moxtet.h                       | 103 +++++
 6 files changed, 658 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mfd/moxtet.txt
 create mode 100644 drivers/mfd/moxtet.c
 create mode 100644 include/linux/mfd/moxtet.h

diff --git a/Documentation/devicetree/bindings/mfd/moxtet.txt b/Documentation/devicetree/bindings/mfd/moxtet.txt
new file mode 100644
index 000000000000..02b96fbd5ddd
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/moxtet.txt
@@ -0,0 +1,36 @@
+Turris Mox module configuration bus (over SPI)
+
+Required properties:
+ - compatible		: Should be "cznic,moxtet".
+ - #address-cells	: Has to be 1
+ - #size-cells		: Has to be 0
+For other required and optional properties of SPI slave
+nodes please refer to ../spi/spi-bus.txt.
+
+Required properties of subnodes:
+ - reg			: Should be position on the Moxtet bus
+ - moxtet,id		: Should be ID of the Moxtet device connected
+
+The driver finds the devices connected to the bus by itself, but it may be
+needed to reference some of them from other parts of the device tree. In that
+case the devices can be defined as subnodes of the moxtet node.
+
+Example:
+
+	moxtet@1 {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		compatible = "cznic,moxtet";
+		reg = <1>;
+		spi-max-frequency = <1000000>;
+		spi-cpol;
+		spi-cpha;
+
+		moxtet_sfp: moxtet-sfp@0 {
+			compatible = "cznic,moxtet-sfp";
+			gpio-controller;
+			#gpio-cells;
+			reg = <0>;
+			moxtet,id = <1>;
+		}
+	};
diff --git a/MAINTAINERS b/MAINTAINERS
index a5b256b25905..84e60ee83951 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1412,6 +1412,13 @@ F:	drivers/clocksource/timer-prima2.c
 F:	drivers/clocksource/timer-atlas7.c
 N:	[^a-z]sirf
 
+ARM/CZ.NIC TURRIS MOX SUPPORT
+M:	Marek Behun <marek.behun@nic.cz>
+W:	http://mox.turris.cz
+S:	Maintained
+F:	include/mfd/moxtet.h
+F:	drivers/mfd/moxtet.c
+
 ARM/EBSA110 MACHINE SUPPORT
 M:	Russell King <linux@armlinux.org.uk>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 11841f4b7b2b..cb401841e2ac 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -814,6 +814,16 @@ config MFD_MAX8998
 	  additional drivers must be enabled in order to use the functionality
 	  of the device.
 
+config MFD_MOXTET
+	tristate "CZ.NIC Turris Mox module configuration bus"
+	depends on SPI_MASTER && OF
+	help
+	  Say yes here to add support for the module configuration bus found
+	  on CZ.NIC's Turris Mox. This is needed for the ability to read
+	  in what order the modules are connected and to get/set some of
+	  their settings. For example the GPIOs on Mox SFP module are
+	  configured through this bus.
+
 config MFD_MT6397
 	tristate "MediaTek MT6397 PMIC Support"
 	select MFD_CORE
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 5856a9489cbd..338ecf311911 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -159,6 +159,7 @@ max8925-objs			:= max8925-core.o max8925-i2c.o
 obj-$(CONFIG_MFD_MAX8925)	+= max8925.o
 obj-$(CONFIG_MFD_MAX8997)	+= max8997.o max8997-irq.o
 obj-$(CONFIG_MFD_MAX8998)	+= max8998.o max8998-irq.o
+obj-$(CONFIG_MFD_MOXTET)	+= moxtet.o
 
 pcf50633-objs			:= pcf50633-core.o pcf50633-irq.o
 obj-$(CONFIG_MFD_PCF50633)	+= pcf50633.o
diff --git a/drivers/mfd/moxtet.c b/drivers/mfd/moxtet.c
new file mode 100644
index 000000000000..1cd1a62002e7
--- /dev/null
+++ b/drivers/mfd/moxtet.c
@@ -0,0 +1,501 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Turris Mox module configuration bus driver
+ *
+ * Copyright (C) 2018 Marek Behun <marek.behun@nic.cz>
+ */
+
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of_device.h>
+#include <linux/spi/spi.h>
+#include <linux/mfd/moxtet.h>
+
+static ssize_t
+module_id_show(struct device *dev, struct device_attribute *a, char *buf)
+{
+	struct moxtet_device *mdev = to_moxtet_device(dev);
+
+	return sprintf(buf, "0x%x\n", mdev->id);
+}
+static DEVICE_ATTR_RO(module_id);
+
+static ssize_t
+module_name_show(struct device *dev, struct device_attribute *a, char *buf)
+{
+	struct moxtet_device *mdev = to_moxtet_device(dev);
+
+	return sprintf(buf, "%s\n", turris_mox_module_name(mdev->id));
+}
+static DEVICE_ATTR_RO(module_name);
+
+static ssize_t
+input_value_show(struct device *dev, struct device_attribute *a, char *buf)
+{
+	int ret;
+
+	ret = moxtet_device_read(dev);
+	if (ret < 0)
+		return ret;
+
+	return sprintf(buf, "0x%x\n", ret);
+}
+static DEVICE_ATTR_RO(input_value);
+
+static ssize_t
+output_value_show(struct device *dev, struct device_attribute *a, char *buf)
+{
+	int ret;
+
+	ret = moxtet_device_written(dev);
+	if (ret < 0)
+		return ret;
+
+	return sprintf(buf, "0x%x\n", ret);
+}
+
+static ssize_t
+output_value_store(struct device *dev, struct device_attribute *a,
+		   const char *buf, size_t count)
+{
+	unsigned long val;
+	int ret;
+
+	ret = kstrtoul(buf, 0, &val);
+	if (ret < 0)
+		return ret;
+
+	if (val > 0xff)
+		return -ERANGE;
+
+	ret = moxtet_device_write(dev, val);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+static DEVICE_ATTR_RW(output_value);
+
+static struct attribute *moxtet_dev_attrs[] = {
+	&dev_attr_module_id.attr,
+	&dev_attr_module_name.attr,
+	&dev_attr_input_value.attr,
+	&dev_attr_output_value.attr,
+	NULL,
+};
+
+static const struct attribute_group moxtet_dev_group = {
+	.attrs = moxtet_dev_attrs,
+};
+
+static const struct attribute_group *moxtet_dev_groups[] = {
+	&moxtet_dev_group,
+	NULL,
+};
+
+static int moxtet_match(struct device *dev, struct device_driver *drv)
+{
+	struct moxtet_device *mdev = to_moxtet_device(dev);
+	struct moxtet_driver *tdrv = to_moxtet_driver(drv);
+	const enum turris_mox_module_id *t;
+
+	if (of_driver_match_device(dev, drv))
+		return 1;
+
+	if (!tdrv->id_table)
+		return 0;
+
+	for (t = tdrv->id_table; *t; ++t)
+		if (*t == mdev->id)
+			return 1;
+
+	return 0;
+}
+
+struct bus_type moxtet_bus_type = {
+	.name		= "moxtet",
+	.dev_groups	= moxtet_dev_groups,
+	.match		= moxtet_match,
+};
+EXPORT_SYMBOL_GPL(moxtet_bus_type);
+
+int __moxtet_register_driver(struct module *owner,
+			     struct moxtet_driver *mdrv)
+{
+	mdrv->driver.owner = owner;
+	mdrv->driver.bus = &moxtet_bus_type;
+	return driver_register(&mdrv->driver);
+}
+EXPORT_SYMBOL_GPL(__moxtet_register_driver);
+
+static int moxtet_dev_check(struct device *dev, void *data)
+{
+	struct moxtet_device *mdev = to_moxtet_device(dev);
+	struct moxtet_device *new_dev = data;
+
+	if (mdev->moxtet == new_dev->moxtet && mdev->id == new_dev->id &&
+	    mdev->idx == new_dev->idx)
+		return -EBUSY;
+	return 0;
+}
+
+static void moxtet_dev_release(struct device *dev)
+{
+	struct moxtet_device *mdev = to_moxtet_device(dev);
+
+	put_device(mdev->moxtet->dev);
+	kfree(mdev);
+}
+
+static struct moxtet_device *
+moxtet_alloc_device(struct moxtet *moxtet)
+{
+	struct moxtet_device *dev;
+
+	if (!get_device(moxtet->dev))
+		return NULL;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev) {
+		put_device(moxtet->dev);
+		return NULL;
+	}
+
+	dev->moxtet = moxtet;
+	dev->dev.parent = moxtet->dev;
+	dev->dev.bus = &moxtet_bus_type;
+	dev->dev.release = moxtet_dev_release;
+
+	device_initialize(&dev->dev);
+
+	return dev;
+}
+
+static int moxtet_add_device(struct moxtet_device *dev)
+{
+	static DEFINE_MUTEX(add_mutex);
+	int ret;
+
+	if (dev->idx >= TURRIS_MOX_MAX_MODULES || dev->id > 0xf)
+		return -EINVAL;
+
+	dev_set_name(&dev->dev, "moxtet-%s.%u",
+		     turris_mox_module_name(dev->id), dev->idx);
+
+	mutex_lock(&add_mutex);
+
+	ret = bus_for_each_dev(&moxtet_bus_type, NULL, dev,
+			       moxtet_dev_check);
+	if (ret)
+		goto done;
+
+	ret = device_add(&dev->dev);
+	if (ret < 0)
+		dev_err(dev->moxtet->dev, "can't add %s, status %d\n",
+			dev_name(dev->moxtet->dev), ret);
+
+done:
+	mutex_unlock(&add_mutex);
+	return ret;
+}
+
+static int __unregister(struct device *dev, void *null)
+{
+	if (dev->of_node) {
+		of_node_clear_flag(dev->of_node, OF_POPULATED);
+		of_node_put(dev->of_node);
+	}
+
+	device_unregister(dev);
+
+	return 0;
+}
+
+static struct moxtet_device *
+of_register_moxtet_device(struct moxtet *moxtet, struct device_node *nc)
+{
+	struct moxtet_device *dev;
+	u32 val;
+	int ret;
+
+	dev = moxtet_alloc_device(moxtet);
+	if (!dev) {
+		dev_err(moxtet->dev,
+			"Moxtet device alloc error for %pOF\n", nc);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	ret = of_property_read_u32(nc, "reg", &val);
+	if (ret || val >= TURRIS_MOX_MAX_MODULES) {
+		dev_err(moxtet->dev, "%pOF has no valid 'reg' property (%d)\n",
+			nc, ret);
+		goto err_put;
+	}
+	dev->idx = val;
+
+	ret = of_property_read_u32(nc, "moxtet,id", &val);
+	if (ret || val > 0xf) {
+		dev_err(moxtet->dev,
+			"%pOF has no valid 'moxtet,id' property (%d)\n", nc,
+			ret);
+		goto err_put;
+	}
+	dev->id = val;
+
+	if (moxtet->modules[dev->idx] != dev->id) {
+		dev_err(moxtet->dev,
+			"%pOF requested Moxtet device ID 0x%x, 0x%x found\n",
+			nc, dev->id, moxtet->modules[dev->idx]);
+		goto err_put;
+	}
+
+	of_node_get(nc);
+	dev->dev.of_node = nc;
+
+	ret = moxtet_add_device(dev);
+	if (ret) {
+		dev_err(moxtet->dev,
+			"Moxtet device register error for %pOF\n", nc);
+		of_node_put(nc);
+		goto err_put;
+	}
+
+	return dev;
+
+err_put:
+	put_device(&dev->dev);
+	return ERR_PTR(ret);
+}
+
+static void of_register_moxtet_devices(struct moxtet *moxtet)
+{
+	struct moxtet_device *dev;
+	struct device_node *nc;
+
+	if (!moxtet->dev->of_node)
+		return;
+
+	for_each_available_child_of_node(moxtet->dev->of_node, nc) {
+		if (of_node_test_and_set_flag(nc, OF_POPULATED))
+			continue;
+		dev = of_register_moxtet_device(moxtet, nc);
+		if (IS_ERR(dev)) {
+			dev_warn(moxtet->dev,
+				 "Failed to create Moxtet device for %pOF\n",
+				 nc);
+			of_node_clear_flag(nc, OF_POPULATED);
+		}
+	}
+}
+
+static void
+moxtet_register_devices_from_topology(struct moxtet *moxtet)
+{
+	struct moxtet_device *dev;
+	int i, ret;
+
+	for (i = 0; i < moxtet->count; ++i) {
+		dev = moxtet_alloc_device(moxtet);
+		if (!dev) {
+			dev_err(moxtet->dev, "Moxtet device %u alloc error\n",
+				i);
+			continue;
+		}
+
+		dev->idx = i;
+		dev->id = moxtet->modules[i];
+
+		ret = moxtet_add_device(dev);
+		if (ret && ret != -EBUSY) {
+			put_device(&dev->dev);
+			dev_err(moxtet->dev,
+				"Moxtet device %u register error: %i\n", i,
+				ret);
+		}
+	}
+}
+
+static int moxtet_find_topology(struct moxtet *moxtet)
+{
+	u8 buf[TURRIS_MOX_MAX_MODULES];
+	int i, ret;
+
+	ret = spi_read(to_spi_device(moxtet->dev), buf, TURRIS_MOX_MAX_MODULES);
+	if (ret < 0)
+		return ret;
+
+	if (buf[0] == TURRIS_MOX_CPU_ID_EMMC) {
+		dev_info(moxtet->dev, "Found eMMC Turris Mox CPU module\n");
+	} else if (buf[0] == TURRIS_MOX_CPU_ID_SD) {
+		dev_info(moxtet->dev, "Found SD Turris Mox CPU module\n");
+	} else {
+		dev_err(moxtet->dev, "Invalid Turris Mox CPU module 0x%02x\n",
+			buf[0]);
+		return -ENODEV;
+	}
+
+	moxtet->count = 0;
+
+	for (i = 1; i < TURRIS_MOX_MAX_MODULES; ++i) {
+		int module_id;
+
+		if (buf[i] == 0xff)
+			break;
+
+		module_id = buf[i] & 0xf;
+
+		moxtet->modules[i-1] = module_id;
+		++moxtet->count;
+
+		switch (module_id) {
+		case TURRIS_MOX_MODULE_SFP:
+			dev_info(moxtet->dev, "SFP module found\n");
+			break;
+		case TURRIS_MOX_MODULE_PCI:
+			dev_info(moxtet->dev, "PCIe module found\n");
+			break;
+		case TURRIS_MOX_MODULE_TOPAZ:
+			dev_info(moxtet->dev, "Topaz Switch module found\n");
+			break;
+		case TURRIS_MOX_MODULE_PERIDOT:
+			dev_info(moxtet->dev, "Peridot Switch module found\n");
+			break;
+		default:
+			dev_info(moxtet->dev,
+				 "Unknown Moxtet module found (ID 0x%02x)\n",
+				 module_id);
+		}
+	}
+
+	return 0;
+}
+
+int moxtet_device_read(struct device *dev)
+{
+	struct moxtet_device *mdev = to_moxtet_device(dev);
+	struct moxtet *moxtet = mdev->moxtet;
+	u8 buf[TURRIS_MOX_MAX_MODULES];
+	struct spi_transfer xfer = {
+		.rx_buf = buf,
+		.tx_buf = moxtet->tx,
+		.len = moxtet->count + 1
+	};
+	int ret;
+
+	if (mdev->idx >= moxtet->count)
+		return -EINVAL;
+
+	mutex_lock(&moxtet->lock);
+
+	ret = spi_sync_transfer(to_spi_device(moxtet->dev), &xfer, 1);
+
+	mutex_unlock(&moxtet->lock);
+
+	if (ret < 0)
+		return ret;
+
+	return buf[mdev->idx + 1] >> 4;
+}
+EXPORT_SYMBOL_GPL(moxtet_device_read);
+
+int moxtet_device_write(struct device *dev, u8 val)
+{
+	struct moxtet_device *mdev = to_moxtet_device(dev);
+	struct moxtet *moxtet = mdev->moxtet;
+	int ret;
+
+	if (mdev->idx >= moxtet->count)
+		return -EINVAL;
+
+	mutex_lock(&moxtet->lock);
+
+	moxtet->tx[moxtet->count - mdev->idx] = val;
+
+	ret = spi_write(to_spi_device(moxtet->dev), moxtet->tx,
+			moxtet->count + 1);
+
+	mutex_unlock(&moxtet->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(moxtet_device_write);
+
+int moxtet_device_written(struct device *dev)
+{
+	struct moxtet_device *mdev = to_moxtet_device(dev);
+	struct moxtet *moxtet = mdev->moxtet;
+
+	if (mdev->idx >= moxtet->count)
+		return -EINVAL;
+
+	return moxtet->tx[moxtet->count - mdev->idx];
+}
+EXPORT_SYMBOL_GPL(moxtet_device_written);
+
+static int moxtet_probe(struct spi_device *spi)
+{
+	struct moxtet *moxtet;
+	int ret;
+
+	ret = spi_setup(spi);
+	if (ret < 0)
+		return ret;
+
+	moxtet = devm_kzalloc(&spi->dev, sizeof(struct moxtet),
+			      GFP_KERNEL);
+	if (!moxtet)
+		return -ENOMEM;
+
+	moxtet->dev = &spi->dev;
+	spi_set_drvdata(spi, moxtet);
+
+	mutex_init(&moxtet->lock);
+
+	ret = moxtet_find_topology(moxtet);
+	if (ret < 0)
+		return ret;
+
+	of_register_moxtet_devices(moxtet);
+	moxtet_register_devices_from_topology(moxtet);
+
+	return 0;
+}
+
+static int moxtet_remove(struct spi_device *spi)
+{
+	struct moxtet *moxtet = spi_get_drvdata(spi);
+	int dummy;
+
+	dummy = device_for_each_child(moxtet->dev, NULL, __unregister);
+
+	mutex_destroy(&moxtet->lock);
+
+	return 0;
+}
+
+static const struct of_device_id moxtet_dt_ids[] = {
+	{ .compatible = "cznic,moxtet" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, moxtet_dt_ids);
+
+static struct spi_driver moxtet_driver = {
+	.driver = {
+		.name		= "moxtet",
+		.of_match_table = moxtet_dt_ids,
+	},
+	.probe		= moxtet_probe,
+	.remove		= moxtet_remove,
+};
+module_spi_driver(moxtet_driver);
+
+static int __init moxtet_init(void)
+{
+	return bus_register(&moxtet_bus_type);
+}
+
+postcore_initcall(moxtet_init);
+
+MODULE_AUTHOR("Marek Behun <marek.behun@nic.cz>");
+MODULE_DESCRIPTION("CZ.NIC's Turris Mox module configuration bus");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/mfd/moxtet.h b/include/linux/mfd/moxtet.h
new file mode 100644
index 000000000000..f818039c2c2e
--- /dev/null
+++ b/include/linux/mfd/moxtet.h
@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Turris Mox module configuration bus driver
+ *
+ * Copyright (C) 2018 Marek Behun <marek.behun@nic.cz>
+ */
+
+#ifndef __LINUX_MFD_MOXTET_H
+#define __LINUX_MFD_MOXTET_H
+
+#include <linux/device.h>
+#include <linux/mutex.h>
+
+#define TURRIS_MOX_MAX_MODULES	10
+
+enum turris_mox_cpu_module_id {
+	TURRIS_MOX_CPU_ID_EMMC	= 0x00,
+	TURRIS_MOX_CPU_ID_SD	= 0x10,
+};
+
+enum turris_mox_module_id {
+	TURRIS_MOX_MODULE_SFP		= 0x01,
+	TURRIS_MOX_MODULE_PCI		= 0x02,
+	TURRIS_MOX_MODULE_TOPAZ		= 0x03,
+	TURRIS_MOX_MODULE_PERIDOT	= 0x04,
+};
+
+static inline const char *turris_mox_module_name(unsigned int id)
+{
+	switch (id) {
+	case TURRIS_MOX_MODULE_SFP:
+		return "sfp";
+	case TURRIS_MOX_MODULE_PCI:
+		return "pci";
+	case TURRIS_MOX_MODULE_TOPAZ:
+		return "topaz";
+	case TURRIS_MOX_MODULE_PERIDOT:
+		return "peridot";
+	default:
+		return "unknown";
+	}
+}
+
+extern struct bus_type moxtet_type;
+
+struct moxtet {
+	struct device	*dev;
+	struct mutex	lock;
+	u8		modules[TURRIS_MOX_MAX_MODULES];
+	int		count;
+	u8		tx[TURRIS_MOX_MAX_MODULES];
+	char		module_topology[128];
+};
+
+struct moxtet_driver {
+	const enum turris_mox_module_id	*id_table;
+	struct device_driver		driver;
+};
+
+static inline struct moxtet_driver *
+to_moxtet_driver(struct device_driver *drv)
+{
+	if (!drv)
+		return NULL;
+	return container_of(drv, struct moxtet_driver, driver);
+}
+
+extern int __moxtet_register_driver(struct module *owner,
+				    struct moxtet_driver *mdrv);
+
+static inline void moxtet_unregister_driver(struct moxtet_driver *mdrv)
+{
+	if (mdrv)
+		driver_unregister(&mdrv->driver);
+}
+
+#define moxtet_register_driver(driver) \
+	__moxtet_register_driver(THIS_MODULE, driver)
+
+#define module_moxtet_driver(__moxtet_driver) \
+	module_driver(__moxtet_driver, moxtet_register_driver, \
+			moxtet_unregister_driver)
+
+struct moxtet_device {
+	struct device			dev;
+	struct moxtet			*moxtet;
+	enum turris_mox_module_id	id;
+	unsigned int			idx;
+};
+
+extern int moxtet_device_read(struct device *dev);
+extern int moxtet_device_write(struct device *dev, u8 val);
+extern int moxtet_device_written(struct device *dev);
+
+static inline struct moxtet_device *
+to_moxtet_device(struct device *dev)
+{
+	if (!dev)
+		return NULL;
+	return container_of(dev, struct moxtet_device, dev);
+}
+
+#endif /* __LINUX_MFD_MOXTET_H */
-- 
2.16.4

[PATCH mfd+gpio 2/2] drivers: gpio: Add support for GPIOs over Moxtet bus

[Marek Behún]

This adds support for interpreting the input and output bits of one
device on Moxtet bus as GPIOs.
This is needed for example by the SFP cage module of Turris Mox.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
---
 .../devicetree/bindings/gpio/gpio-moxtet.txt       |  31 +++
 MAINTAINERS                                        |   1 +
 drivers/gpio/Kconfig                               |   9 +
 drivers/gpio/Makefile                              |   1 +
 drivers/gpio/gpio-moxtet.c                         | 209 +++++++++++++++++++++
 5 files changed, 251 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/gpio/gpio-moxtet.txt
 create mode 100644 drivers/gpio/gpio-moxtet.c

diff --git a/Documentation/devicetree/bindings/gpio/gpio-moxtet.txt b/Documentation/devicetree/bindings/gpio/gpio-moxtet.txt
new file mode 100644
index 000000000000..64a9a1bfd4cf
--- /dev/null
+++ b/Documentation/devicetree/bindings/gpio/gpio-moxtet.txt
@@ -0,0 +1,31 @@
+Turris Mox Moxtet GPIO expander
+
+Required properties:
+ - compatible		: Should be "cznic,moxtet-gpio".
+ - gpio-controller	: Marks the device node as a GPIO controller.
+ - #gpio-cells		: Should be two. For consumer use see gpio.txt.
+ - moxtet,input-mask	: Bitmask. Those bits which correspond to input GPIOs
+			  when read from Moxtet bus should be set here.
+			  For example if bit 0 and bit 3 are input GPIO bits,
+			  this should be set to 0x9.
+			  Since there are only 4 input bits, 0xf is max value.
+ - moxtet,output-mask	: Bitmask. Those bits which correspond to output GPIOs
+			  when written to Moxtet bus should be set here.
+			  For example if bit 1 and bit 6 are output GPIO bits,
+			  this should be set to 0x41.
+			  Since there are at most 8 output bits, 0xff is max
+			  value.
+Other properties are required for a moxtet bus device, please refer to
+Documentation/devicetree/bindings/mfd/moxtet.txt.
+
+Example:
+
+	moxtet_sfp: moxtet-sfp@0 {
+		compatible = "cznic,moxtet-gpio";
+		gpio-controller;
+		#gpio-cells;
+		reg = <0>;
+		moxtet,id = <1>;
+		moxtet,input-mask = <0x7>;
+		moxtet,output-mask = <0x3>;
+	}
diff --git a/MAINTAINERS b/MAINTAINERS
index 84e60ee83951..0ca4e5302054 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1417,6 +1417,7 @@ M:	Marek Behun <marek.behun@nic.cz>
 W:	http://mox.turris.cz
 S:	Maintained
 F:	include/mfd/moxtet.h
+F:	drivers/gpio/gpio-moxtet.c
 F:	drivers/mfd/moxtet.c
 
 ARM/EBSA110 MACHINE SUPPORT
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index b8cbf5081389..2c0202aa91d0 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1055,6 +1055,15 @@ config GPIO_MAX77620
 	  driver also provides interrupt support for each of the gpios.
 	  Say yes here to enable the max77620 to be used as gpio controller.
 
+config GPIO_MOXTET
+	tristate "Turris Mox Moxtet bus GPIO expander"
+	depends on MFD_MOXTET
+	help
+	  Say yes here if you are building for the Turris Mox router.
+	  This is the driver needed for configuring the GPIOs via the Moxtet
+	  bus. For example the Mox module with SFP cage needs this driver
+	  so that phylink can use corresponding GPIOs.
+
 config GPIO_MSIC
 	bool "Intel MSIC mixed signal gpio support"
 	depends on (X86 || COMPILE_TEST) && MFD_INTEL_MSIC
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 80d58c2de730..e119b3b87f1f 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -85,6 +85,7 @@ obj-$(CONFIG_GPIO_MC9S08DZ60)	+= gpio-mc9s08dz60.o
 obj-$(CONFIG_GPIO_ML_IOH)	+= gpio-ml-ioh.o
 obj-$(CONFIG_GPIO_MM_LANTIQ)	+= gpio-mm-lantiq.o
 obj-$(CONFIG_GPIO_MOCKUP)      += gpio-mockup.o
+obj-$(CONFIG_GPIO_MOXTET)	+= gpio-moxtet.o
 obj-$(CONFIG_GPIO_MPC5200)	+= gpio-mpc5200.o
 obj-$(CONFIG_GPIO_MPC8XXX)	+= gpio-mpc8xxx.o
 obj-$(CONFIG_GPIO_MSIC)		+= gpio-msic.o
diff --git a/drivers/gpio/gpio-moxtet.c b/drivers/gpio/gpio-moxtet.c
new file mode 100644
index 000000000000..d0b50581118d
--- /dev/null
+++ b/drivers/gpio/gpio-moxtet.c
@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Turris Mox Moxtet GPIO expander
+ *
+ *  Copyright (C) 2018 Marek Behun <marek.behun@nic.cz>
+ */
+
+#include <linux/gpio/consumer.h>
+#include <linux/gpio.h>
+#include <linux/mfd/moxtet.h>
+#include <linux/module.h>
+#include <linux/of_gpio.h>
+
+struct moxtet_gpio_chip {
+	struct device		*dev;
+	struct gpio_chip	gpio_chip;
+	u8			in_mask;
+	u8			out_mask;
+};
+
+static int moxtet_gpio_dir_mask(struct gpio_chip *gc, unsigned int offset,
+				int *dir, u8 *mask)
+{
+	struct moxtet_gpio_chip *chip = gpiochip_get_data(gc);
+	int i;
+
+	*dir = 0;
+	for (i = 0; i < 4; ++i) {
+		*mask = 1 << i;
+		if (*mask & chip->in_mask) {
+			if (offset == 0)
+				return 0;
+			--offset;
+		}
+	}
+
+	*dir = 1;
+	for (i = 0; i < 8; ++i) {
+		*mask = 1 << i;
+		if (*mask & chip->out_mask) {
+			if (offset == 0)
+				return 0;
+		}
+	}
+
+	return -EINVAL;
+}
+
+static int moxtet_gpio_get_value(struct gpio_chip *gc, unsigned int offset)
+{
+	struct moxtet_gpio_chip *chip = gpiochip_get_data(gc);
+	int ret, dir;
+	u8 mask;
+
+	if (moxtet_gpio_dir_mask(gc, offset, &dir, &mask) < 0)
+		return -EINVAL;
+
+	if (dir)
+		ret = moxtet_device_written(chip->dev);
+	else
+		ret = moxtet_device_read(chip->dev);
+
+	if (ret < 0)
+		return ret;
+
+	return (ret & mask) ? 1 : 0;
+}
+
+static void moxtet_gpio_set_value(struct gpio_chip *gc, unsigned int offset,
+				  int val)
+{
+	struct moxtet_gpio_chip *chip = gpiochip_get_data(gc);
+	int state, dir;
+	u8 mask;
+
+	if (moxtet_gpio_dir_mask(gc, offset, &dir, &mask) < 0)
+		return;
+
+	/* cannot change input GPIO */
+	if (!dir)
+		return;
+
+	state = moxtet_device_written(chip->dev);
+	if (state < 0)
+		return;
+
+	if (val)
+		state |= mask;
+	else
+		state &= ~mask;
+
+	moxtet_device_write(chip->dev, state);
+}
+
+static int moxtet_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+	int dir;
+	u8 mask;
+
+	if (moxtet_gpio_dir_mask(gc, offset, &dir, &mask) < 0)
+		return -EINVAL;
+
+	return dir;
+}
+
+static int moxtet_gpio_direction_input(struct gpio_chip *gc,
+				       unsigned int offset)
+{
+	int dir;
+	u8 mask;
+
+	if (moxtet_gpio_dir_mask(gc, offset, &dir, &mask) < 0)
+		return -EINVAL;
+
+	if (dir)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int moxtet_gpio_direction_output(struct gpio_chip *gc,
+					unsigned int offset, int val)
+{
+	int dir;
+	u8 mask;
+
+	if (moxtet_gpio_dir_mask(gc, offset, &dir, &mask) < 0)
+		return -EINVAL;
+
+	if (!dir)
+		return -EINVAL;
+
+	moxtet_gpio_set_value(gc, offset, val);
+	return 0;
+}
+
+static int moxtet_gpio_probe(struct device *dev)
+{
+	struct moxtet_gpio_chip *chip;
+	struct device_node *nc = dev->of_node;
+	int ret;
+	u32 val;
+
+	chip = devm_kzalloc(dev, sizeof(*chip), GFP_KERNEL);
+	if (!chip)
+		return -ENOMEM;
+
+	chip->dev = dev;
+	chip->gpio_chip.parent = dev;
+
+	ret = of_property_read_u32(nc, "moxtet,input-mask", &val);
+	if (ret < 0 || val > 0xf) {
+		dev_err(dev,
+			"%pOF has no valid 'moxtet,input-mask' property\n", nc);
+		return ret < 0 ? ret : -ERANGE;
+	}
+	chip->in_mask = val;
+
+	ret = of_property_read_u32(nc, "moxtet,output-mask", &val);
+	if (ret < 0 || val > 0xff) {
+		dev_err(dev,
+			"%pOF has no valid 'moxtet,output-mask' property\n",
+			nc);
+		return ret < 0 ? ret : -ERANGE;
+	}
+	chip->out_mask = val;
+
+	if (!chip->in_mask && !chip->out_mask) {
+		dev_err(dev, "%pOF has zero GPIOs defined\n", nc);
+		return -EINVAL;
+	}
+
+	dev_set_drvdata(dev, chip);
+
+	chip->gpio_chip.label = dev_name(dev);
+	chip->gpio_chip.get_direction = moxtet_gpio_get_direction;
+	chip->gpio_chip.direction_input = moxtet_gpio_direction_input;
+	chip->gpio_chip.direction_output = moxtet_gpio_direction_output;
+	chip->gpio_chip.get = moxtet_gpio_get_value;
+	chip->gpio_chip.set = moxtet_gpio_set_value;
+	chip->gpio_chip.base = -1;
+
+	chip->gpio_chip.ngpio = hweight8(chip->in_mask) +
+				hweight8(chip->out_mask);
+
+	chip->gpio_chip.can_sleep = true;
+	chip->gpio_chip.owner = THIS_MODULE;
+
+	return devm_gpiochip_add_data(dev, &chip->gpio_chip, chip);
+}
+
+static const struct of_device_id moxtet_gpio_dt_ids[] = {
+	{ .compatible = "cznic,moxtet-gpio" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, moxtet_gpio_dt_ids);
+
+static struct moxtet_driver moxtet_gpio_driver = {
+	.driver = {
+		.name		= "moxtet-gpio",
+		.of_match_table	= moxtet_gpio_dt_ids,
+		.probe		= moxtet_gpio_probe,
+	},
+};
+module_moxtet_driver(moxtet_gpio_driver);
+
+MODULE_AUTHOR("Marek Behun <marek.behun@nic.cz>");
+MODULE_DESCRIPTION("Turris Mox Moxtet GPIO expander");
+MODULE_LICENSE("GPL v2");
-- 
2.16.4

[PATCH mfd+gpio] Request (Linus Walleij + Lee Jones)

[Marek Behun]

Hi Linus and Lee,
these two patches touch two different subsystems (mfd + gpio) and
should be applyied one after another (the gpio part is dependant on the
mfd part).
The patches are based on mfd-next-4.19. I can send another copy based
on gpio/devel.
Could you two, Linus and Lee, work together on applying these patches?
I don't know how this is usually solved...
Thanks.

Marek

Re: [PATCH mfd+gpio 1/2] drivers: mfd: Add support for Moxtet bus

[Dan Carpenter]

Hi Marek,

Thank you for the patch! Perhaps something to improve:

url:    https://github.com/0day-ci/linux/commits/Marek-Beh-n/drivers-mfd-Add-support-for-Moxtet-bus/20180831-031806
base:   https://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd.git for-mfd-next

smatch warnings:
drivers/mfd/moxtet.c:267 of_register_moxtet_device() warn: passing zero to 'ERR_PTR'

# https://github.com/0day-ci/linux/commit/316bda5c94917aa3b0a67c3cf79cca211d08138d
git remote add linux-review https://github.com/0day-ci/linux
git remote update linux-review
git checkout 316bda5c94917aa3b0a67c3cf79cca211d08138d
vim +/ERR_PTR +267 drivers/mfd/moxtet.c

316bda5c Marek Behún 2018-08-30  213  
316bda5c Marek Behún 2018-08-30  214  static struct moxtet_device *
316bda5c Marek Behún 2018-08-30  215  of_register_moxtet_device(struct moxtet *moxtet, struct device_node *nc)
316bda5c Marek Behún 2018-08-30  216  {
316bda5c Marek Behún 2018-08-30  217  	struct moxtet_device *dev;
316bda5c Marek Behún 2018-08-30  218  	u32 val;
316bda5c Marek Behún 2018-08-30  219  	int ret;
316bda5c Marek Behún 2018-08-30  220  
316bda5c Marek Behún 2018-08-30  221  	dev = moxtet_alloc_device(moxtet);
316bda5c Marek Behún 2018-08-30  222  	if (!dev) {
316bda5c Marek Behún 2018-08-30  223  		dev_err(moxtet->dev,
316bda5c Marek Behún 2018-08-30  224  			"Moxtet device alloc error for %pOF\n", nc);
316bda5c Marek Behún 2018-08-30  225  		return ERR_PTR(-ENOMEM);
316bda5c Marek Behún 2018-08-30  226  	}
316bda5c Marek Behún 2018-08-30  227  
316bda5c Marek Behún 2018-08-30  228  	ret = of_property_read_u32(nc, "reg", &val);
316bda5c Marek Behún 2018-08-30  229  	if (ret || val >= TURRIS_MOX_MAX_MODULES) {
                                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
No error code set.  It means we return NULL.  Presumably it leads to a
NULL dereference in the caller?

316bda5c Marek Behún 2018-08-30  230  		dev_err(moxtet->dev, "%pOF has no valid 'reg' property (%d)\n",
316bda5c Marek Behún 2018-08-30  231  			nc, ret);
316bda5c Marek Behún 2018-08-30  232  		goto err_put;
316bda5c Marek Behún 2018-08-30  233  	}
316bda5c Marek Behún 2018-08-30  234  	dev->idx = val;
316bda5c Marek Behún 2018-08-30  235  
316bda5c Marek Behún 2018-08-30  236  	ret = of_property_read_u32(nc, "moxtet,id", &val);
316bda5c Marek Behún 2018-08-30  237  	if (ret || val > 0xf) {
                                                   ^^^^^^^^^

316bda5c Marek Behún 2018-08-30  238  		dev_err(moxtet->dev,
316bda5c Marek Behún 2018-08-30  239  			"%pOF has no valid 'moxtet,id' property (%d)\n", nc,
316bda5c Marek Behún 2018-08-30  240  			ret);
316bda5c Marek Behún 2018-08-30  241  		goto err_put;
316bda5c Marek Behún 2018-08-30  242  	}
316bda5c Marek Behún 2018-08-30  243  	dev->id = val;
316bda5c Marek Behún 2018-08-30  244  
316bda5c Marek Behún 2018-08-30  245  	if (moxtet->modules[dev->idx] != dev->id) {
316bda5c Marek Behún 2018-08-30  246  		dev_err(moxtet->dev,
316bda5c Marek Behún 2018-08-30  247  			"%pOF requested Moxtet device ID 0x%x, 0x%x found\n",
316bda5c Marek Behún 2018-08-30  248  			nc, dev->id, moxtet->modules[dev->idx]);
316bda5c Marek Behún 2018-08-30  249  		goto err_put;
                                                ^^^^^^^^^^^^

316bda5c Marek Behún 2018-08-30  250  	}
316bda5c Marek Behún 2018-08-30  251  
316bda5c Marek Behún 2018-08-30  252  	of_node_get(nc);
316bda5c Marek Behún 2018-08-30  253  	dev->dev.of_node = nc;
316bda5c Marek Behún 2018-08-30  254  
316bda5c Marek Behún 2018-08-30  255  	ret = moxtet_add_device(dev);
316bda5c Marek Behún 2018-08-30  256  	if (ret) {
316bda5c Marek Behún 2018-08-30  257  		dev_err(moxtet->dev,
316bda5c Marek Behún 2018-08-30  258  			"Moxtet device register error for %pOF\n", nc);
316bda5c Marek Behún 2018-08-30  259  		of_node_put(nc);
316bda5c Marek Behún 2018-08-30  260  		goto err_put;
316bda5c Marek Behún 2018-08-30  261  	}
316bda5c Marek Behún 2018-08-30  262  
316bda5c Marek Behún 2018-08-30  263  	return dev;
316bda5c Marek Behún 2018-08-30  264  
316bda5c Marek Behún 2018-08-30  265  err_put:
316bda5c Marek Behún 2018-08-30  266  	put_device(&dev->dev);
316bda5c Marek Behún 2018-08-30 @267  	return ERR_PTR(ret);
316bda5c Marek Behún 2018-08-30  268  }
316bda5c Marek Behún 2018-08-30  269  

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Re: [PATCH mfd+gpio] Request (Linus Walleij + Lee Jones)

[Linus Walleij]

On Thu, Aug 30, 2018 at 4:48 PM Marek Behun <marek.behun@nic.cz> wrote:

> Hi Linus and Lee,
> these two patches touch two different subsystems (mfd + gpio) and
> should be applyied one after another (the gpio part is dependant on the
> mfd part).
> The patches are based on mfd-next-4.19. I can send another copy based
> on gpio/devel.
> Could you two, Linus and Lee, work together on applying these patches?
> I don't know how this is usually solved...

If they need to go into the same merge window this is usually solved
by me ACKing the GPIO patches and Lee applying all of it to
the MFD tree then providing an immutable git branch to me if
I need the same changes in my tree.

Yours,
Linus Walleij

Re: [PATCH mfd+gpio 2/2] drivers: gpio: Add support for GPIOs over Moxtet bus

[Linus Walleij]

Hi Marek!

Your DT bindings patch should ideally be in a separate patch and
must be sent to devicetree@vger.kernel.org as well.

On Thu, Aug 30, 2018 at 4:44 PM Marek Behún <marek.behun@nic.cz> wrote:

> + - moxtet,input-mask   : Bitmask. Those bits which correspond to input GPIOs
> +                         when read from Moxtet bus should be set here.
> +                         For example if bit 0 and bit 3 are input GPIO bits,
> +                         this should be set to 0x9.
> +                         Since there are only 4 input bits, 0xf is max value.
> + - moxtet,output-mask  : Bitmask. Those bits which correspond to output GPIOs
> +                         when written to Moxtet bus should be set here.
> +                         For example if bit 1 and bit 6 are output GPIO bits,
> +                         this should be set to 0x41.
> +                         Since there are at most 8 output bits, 0xff is max
> +                         value.

Please don't do it like this. Let the consumers decide if they want
to use a certain line as input or output.

Enumerate ALL GPIOs from 0 to N and let a consumer pick
GPIO x and then decide if it will be used as input or output.
Re-enumerating the GPIOs presented from the chip is complicating
things by shuffleing around the local offset (HW numbering)
space.

For GPIOs that are not usable at all, use the
gpio-reserved-ranges = <> property, see gpio.txt

If you want to indicate that some lines can just be used for
input and some can just be used for output and some cannot
be used at all, let the .set_direction_output() and
.set_direction_input() callbacks fail for these pins with
-EINVAL or so.

If these masks cannot be derived from the compatible
strings, then create generic bindings to mark lines
as input-only or output-only in gpio.txt and use the
same syntax as gpio-reserved-ranges, and handle it
in the gpiolib just as with gpio-reserved-ranges, not
in your local driver.

For example gpio-output-only-ranges and
gpio-input-only-ranges.

But first convince us that you really need that.

> +#include <linux/gpio/consumer.h>
> +#include <linux/gpio.h>

This is a driver so only #include <linux/gpio/driver.h>
Skip the two above.

> +#include <linux/mfd/moxtet.h>
> +#include <linux/module.h>
> +#include <linux/of_gpio.h>

You don't need this either. Delete that include.

> +static int moxtet_gpio_dir_mask(struct gpio_chip *gc, unsigned int offset,
> +                               int *dir, u8 *mask)
> +{
> +       struct moxtet_gpio_chip *chip = gpiochip_get_data(gc);
> +       int i;
> +
> +       *dir = 0;
> +       for (i = 0; i < 4; ++i) {
> +               *mask = 1 << i;

#include <linux/bitops.h>

*mask = BIT(i);

> +               if (*mask & chip->in_mask) {
> +                       if (offset == 0)
> +                               return 0;
> +                       --offset;
> +               }
> +       }
> +
> +       *dir = 1;
> +       for (i = 0; i < 8; ++i) {
> +               *mask = 1 << i;
> +               if (*mask & chip->out_mask) {
> +                       if (offset == 0)
> +                               return 0;
> +               }
> +       }
> +
> +       return -EINVAL;
> +}

This looks convoluted and I think will go away with my suggestion to
cut the masks.

Otherwise use primitives such as for_each_set_bit() etc.

> +static int moxtet_gpio_get_value(struct gpio_chip *gc, unsigned int offset)
> +{
> +       struct moxtet_gpio_chip *chip = gpiochip_get_data(gc);
> +       int ret, dir;
> +       u8 mask;
> +
> +       if (moxtet_gpio_dir_mask(gc, offset, &dir, &mask) < 0)
> +               return -EINVAL;
> +
> +       if (dir)
> +               ret = moxtet_device_written(chip->dev);
> +       else
> +               ret = moxtet_device_read(chip->dev);
> +
> +       if (ret < 0)
> +               return ret;
> +
> +       return (ret & mask) ? 1 : 0;
> +}
> +
> +static void moxtet_gpio_set_value(struct gpio_chip *gc, unsigned int offset,
> +                                 int val)
> +{
> +       struct moxtet_gpio_chip *chip = gpiochip_get_data(gc);
> +       int state, dir;
> +       u8 mask;
> +
> +       if (moxtet_gpio_dir_mask(gc, offset, &dir, &mask) < 0)
> +               return;

So skip this and trust the consumers to ask for the right GPIO and set
it up.

Yours,
Linus Walleij

Re: [PATCH mfd+gpio 1/2] drivers: mfd: Add support for Moxtet bus

[Lee Jones]

On Thu, 30 Aug 2018, Marek Behún wrote:

> On the Turris Mox router there can be connected different modules to
> the main CPU board, currently a module with a SFP cage, a module with
> MiniPCIe connector, a 4-port switch module and a 8-port switch module,
> for example:
>   [CPU]-[PCIe]-[8-port switch]-[8-port switch]-[SFP]
> 
> Each of this modules has an input and output shift register, and these
> are connected via SPI to CPU board.
> 
> Via this SPI connection we are able to discover which modules are
> connected and we can also read/write some configuration to the modules.
> Fromi/to each module 8 bits can be read (of which lower 4 bits identify
> the module) and written.
> 
> For example from the module with a SFP cage we can read the LOS,
> TX-FAULT and MOD-DEF0 signals, while we can write TX-DISABLE and
> RATE-SELECT signals.
> 
> Other modules may support something else.
> 
> This driver creates a new bus type, called "moxtet". For each Mox module
> it finds via SPI, it creates a new device on the moxtet bus so that
> drivers can be written for them, for example a gpio driver for the
> module with a SFP cage.
> 
> The topology of how Mox modules are connected can then be read by
> listing /sys/bus/moxtet/devices.
> 
> Signed-off-by: Marek Behún <marek.behun@nic.cz>
> ---
>  Documentation/devicetree/bindings/mfd/moxtet.txt |  36 ++

This should be supplied in a separate patch.

>  MAINTAINERS                                      |   7 +

As above please.

>  drivers/mfd/Kconfig                              |  10 +
>  drivers/mfd/Makefile                             |   1 +
>  drivers/mfd/moxtet.c                             | 501 +++++++++++++++++++++++
>  include/linux/mfd/moxtet.h                       | 103 +++++
>  6 files changed, 658 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mfd/moxtet.txt
>  create mode 100644 drivers/mfd/moxtet.c
>  create mode 100644 include/linux/mfd/moxtet.h
> 
> diff --git a/Documentation/devicetree/bindings/mfd/moxtet.txt b/Documentation/devicetree/bindings/mfd/moxtet.txt
> new file mode 100644
> index 000000000000..02b96fbd5ddd
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/moxtet.txt
> @@ -0,0 +1,36 @@
> +Turris Mox module configuration bus (over SPI)
> +
> +Required properties:
> + - compatible		: Should be "cznic,moxtet".
> + - #address-cells	: Has to be 1
> + - #size-cells		: Has to be 0
> +For other required and optional properties of SPI slave
> +nodes please refer to ../spi/spi-bus.txt.

This line is cut unnecessarily short.

> +Required properties of subnodes:
> + - reg			: Should be position on the Moxtet bus
> + - moxtet,id		: Should be ID of the Moxtet device connected

What is this used for?

> +The driver finds the devices connected to the bus by itself, but it may be
> +needed to reference some of them from other parts of the device tree. In that
> +case the devices can be defined as subnodes of the moxtet node.
> +
> +Example:
> +
> +	moxtet@1 {

Does the device itself have a address, or is it only contactable via
SPI?

> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +		compatible = "cznic,moxtet";
> +		reg = <1>;
> +		spi-max-frequency = <1000000>;
> +		spi-cpol;
> +		spi-cpha;
> +
> +		moxtet_sfp: moxtet-sfp@0 {
> +			compatible = "cznic,moxtet-sfp";
> +			gpio-controller;
> +			#gpio-cells;
> +			reg = <0>;
> +			moxtet,id = <1>;
> +		}
> +	};
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a5b256b25905..84e60ee83951 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1412,6 +1412,13 @@ F:	drivers/clocksource/timer-prima2.c
>  F:	drivers/clocksource/timer-atlas7.c
>  N:	[^a-z]sirf
>  
> +ARM/CZ.NIC TURRIS MOX SUPPORT
> +M:	Marek Behun <marek.behun@nic.cz>
> +W:	http://mox.turris.cz
> +S:	Maintained
> +F:	include/mfd/moxtet.h
> +F:	drivers/mfd/moxtet.c
> +
>  ARM/EBSA110 MACHINE SUPPORT
>  M:	Russell King <linux@armlinux.org.uk>
>  L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 11841f4b7b2b..cb401841e2ac 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -814,6 +814,16 @@ config MFD_MAX8998
>  	  additional drivers must be enabled in order to use the functionality
>  	  of the device.
>  
> +config MFD_MOXTET
> +	tristate "CZ.NIC Turris Mox module configuration bus"
> +	depends on SPI_MASTER && OF
> +	help
> +	  Say yes here to add support for the module configuration bus found
> +	  on CZ.NIC's Turris Mox. This is needed for the ability to read
> +	  in what order the modules are connected and to get/set some of
> +	  their settings. For example the GPIOs on Mox SFP module are
> +	  configured through this bus.
> +
>  config MFD_MT6397
>  	tristate "MediaTek MT6397 PMIC Support"
>  	select MFD_CORE
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 5856a9489cbd..338ecf311911 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -159,6 +159,7 @@ max8925-objs			:= max8925-core.o max8925-i2c.o
>  obj-$(CONFIG_MFD_MAX8925)	+= max8925.o
>  obj-$(CONFIG_MFD_MAX8997)	+= max8997.o max8997-irq.o
>  obj-$(CONFIG_MFD_MAX8998)	+= max8998.o max8998-irq.o
> +obj-$(CONFIG_MFD_MOXTET)	+= moxtet.o
>  
>  pcf50633-objs			:= pcf50633-core.o pcf50633-irq.o
>  obj-$(CONFIG_MFD_PCF50633)	+= pcf50633.o
> diff --git a/drivers/mfd/moxtet.c b/drivers/mfd/moxtet.c
> new file mode 100644
> index 000000000000..1cd1a62002e7
> --- /dev/null
> +++ b/drivers/mfd/moxtet.c
> @@ -0,0 +1,501 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Turris Mox module configuration bus driver
> + *
> + * Copyright (C) 2018 Marek Behun <marek.behun@nic.cz>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of_device.h>
> +#include <linux/spi/spi.h>
> +#include <linux/mfd/moxtet.h>

Alphabetical please.

Right, I can probably save us a both a great deal of time here and
tell you right off of the bat that this is not an MFD.  MFDs will
either use the MFD API or something like of_platform_populate().

Glancing over the reminder of the driver, it looks like an alternative
of MFD or at least MFD-like.  I think drivers/platform would be a
better fit.

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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