Staging: most: add MOST driver's hdm-i2c module

This patch adds the hdm-i2c module of the MOST driver to the kernel's
driver staging area. This module is part of the MOST driver and handles
the I2C interface of the MOST network interface controller.

This patch is needed in order to use the I2C peripheral interface of the
network interface controller.
Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/most/Kconfig

@@ -23,4 +23,6 @@ source "drivers/staging/most/aim-v4l2/Kconfig"
 
 source "drivers/staging/most/hdm-dim2/Kconfig"
 
+source "drivers/staging/most/hdm-i2c/Kconfig"
+
 endif

drivers/staging/most/Makefile

@@ -4,3 +4,4 @@ obj-$(CONFIG_AIM_NETWORK)	+= aim-network/
 obj-$(CONFIG_AIM_SOUND)	+= aim-sound/
 obj-$(CONFIG_AIM_V4L2)	+= aim-v4l2/
 obj-$(CONFIG_HDM_DIM2)	+= hdm-dim2/
+obj-$(CONFIG_HDM_I2C)	+= hdm-i2c/

drivers/staging/most/hdm-i2c/Kconfig

+#
+# MOST I2C configuration
+#
+
+config HDM_I2C
+	tristate "I2C HDM"
+	depends on I2C
+	---help---
+	  Say Y here if you want to connect via I2C to network tranceiver.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called hdm_i2c.

drivers/staging/most/hdm-i2c/Makefile

+obj-$(CONFIG_HDM_I2C) += hdm_i2c.o
+
+ccflags-y += -Idrivers/staging/most/mostcore/

drivers/staging/most/hdm-i2c/hdm_i2c.c

+/*
+ * hdm_i2c.c - Hardware Dependent Module for I2C Interface
+ *
+ * Copyright (C) 2013-2015, Microchip Technology Germany II GmbH & Co. KG
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * This file is licensed under GPLv2.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/err.h>
+
+#include <mostcore.h>
+
+enum { CH_RX, CH_TX, NUM_CHANNELS };
+
+#define MAX_BUFFERS_CONTROL 32
+#define MAX_BUF_SIZE_CONTROL 256
+
+/**
+ * list_first_mbo - get the first mbo from a list
+ * @ptr:	the list head to take the mbo from.
+ */
+#define list_first_mbo(ptr) \
+	list_first_entry(ptr, struct mbo, list)
+
+
+/* IRQ / Polling option */
+static bool polling_req;
+module_param(polling_req, bool, S_IRUGO);
+MODULE_PARM_DESC(polling_req, "Request Polling. Default = 0 (use irq)");
+
+/* Polling Rate */
+static int scan_rate = 100;
+module_param(scan_rate, int, 0644);
+MODULE_PARM_DESC(scan_rate, "Polling rate in times/sec. Default = 100");
+
+struct hdm_i2c {
+	bool is_open[NUM_CHANNELS];
+	bool polling_mode;
+	struct most_interface most_iface;
+	struct most_channel_capability capabilities[NUM_CHANNELS];
+	struct i2c_client *client;
+	struct rx {
+		struct delayed_work dwork;
+		wait_queue_head_t waitq;
+		struct list_head list;
+		struct mutex list_mutex;
+	} rx;
+	char name[64];
+};
+
+#define to_hdm(iface) container_of(iface, struct hdm_i2c, most_iface)
+
+/**
+ * configure_channel - called from MOST core to configure a channel
+ * @iface: interface the channel belongs to
+ * @channel: channel to be configured
+ * @channel_config: structure that holds the configuration information
+ *
+ * Return 0 on success, negative on failure.
+ *
+ * Receives configuration information from MOST core and initialize the
+ * corresponding channel.
+ */
+static int configure_channel(struct most_interface *most_iface,
+			     int ch_idx,
+			     struct most_channel_config *channel_config)
+{
+	struct hdm_i2c *dev = to_hdm(most_iface);
+
+	BUG_ON(ch_idx < 0 || ch_idx >= NUM_CHANNELS);
+	BUG_ON(dev->is_open[ch_idx]);
+
+	if (channel_config->data_type != MOST_CH_CONTROL) {
+		pr_err("bad data type for channel %d\n", ch_idx);
+		return -EPERM;
+	}
+
+	if (channel_config->direction != dev->capabilities[ch_idx].direction) {
+		pr_err("bad direction for channel %d\n", ch_idx);
+		return -EPERM;
+	}
+
+	if (channel_config->direction == MOST_CH_RX) {
+		if (dev->polling_mode)
+			schedule_delayed_work(&dev->rx.dwork,
+					      msecs_to_jiffies(MSEC_PER_SEC / 4));
+	}
+	dev->is_open[ch_idx] = true;
+
+	return 0;
+}
+
+/**
+ * enqueue - called from MOST core to enqueue a buffer for data transfer
+ * @iface: intended interface
+ * @channel: ID of the channel the buffer is intended for
+ * @mbo: pointer to the buffer object
+ *
+ * Return 0 on success, negative on failure.
+ *
+ * Transmit the data over I2C if it is a "write" request or push the buffer into
+ * list if it is an "read" request
+ */
+static int enqueue(struct most_interface *most_iface,
+		   int ch_idx, struct mbo *mbo)
+{
+	struct hdm_i2c *dev = to_hdm(most_iface);
+	int ret;
+
+	BUG_ON(ch_idx < 0 || ch_idx >= NUM_CHANNELS);
+	BUG_ON(!dev->is_open[ch_idx]);
+
+	if (ch_idx == CH_RX) {
+		/* RX */
+		mutex_lock(&dev->rx.list_mutex);
+		list_add_tail(&mbo->list, &dev->rx.list);
+		mutex_unlock(&dev->rx.list_mutex);
+		wake_up_interruptible(&dev->rx.waitq);
+	} else {
+		/* TX */
+		ret = i2c_master_send(dev->client, mbo->virt_address,
+				      mbo->buffer_length);
+		if (ret <= 0) {
+			mbo->processed_length = 0;
+			mbo->status = MBO_E_INVAL;
+		} else {
+			mbo->processed_length = mbo->buffer_length;
+			mbo->status = MBO_SUCCESS;
+		}
+		mbo->complete(mbo);
+	}
+
+	return 0;
+}
+
+/**
+ * poison_channel - called from MOST core to poison buffers of a channel
+ * @iface: pointer to the interface the channel to be poisoned belongs to
+ * @channel_id: corresponding channel ID
+ *
+ * Return 0 on success, negative on failure.
+ *
+ * If channel direction is RX, complete the buffers in list with
+ * status MBO_E_CLOSE
+ */
+static int poison_channel(struct most_interface *most_iface,
+			  int ch_idx)
+{
+	struct hdm_i2c *dev = to_hdm(most_iface);
+	struct mbo *mbo;
+
+	BUG_ON(ch_idx < 0 || ch_idx >= NUM_CHANNELS);
+	BUG_ON(!dev->is_open[ch_idx]);
+
+	dev->is_open[ch_idx] = false;
+
+	if (ch_idx == CH_RX) {
+		mutex_lock(&dev->rx.list_mutex);
+		while (!list_empty(&dev->rx.list)) {
+			mbo = list_first_mbo(&dev->rx.list);
+			list_del(&mbo->list);
+			mutex_unlock(&dev->rx.list_mutex);
+
+			mbo->processed_length = 0;
+			mbo->status = MBO_E_CLOSE;
+			mbo->complete(mbo);
+
+			mutex_lock(&dev->rx.list_mutex);
+		}
+		mutex_unlock(&dev->rx.list_mutex);
+		wake_up_interruptible(&dev->rx.waitq);
+	}
+
+	return 0;
+}
+
+static void request_netinfo(struct most_interface *most_iface,
+			    int ch_idx)
+{
+	pr_info("request_netinfo()\n");
+}
+
+static void do_rx_work(struct hdm_i2c *dev)
+{
+	struct mbo *mbo;
+	unsigned char msg[MAX_BUF_SIZE_CONTROL];
+	int ret, ch_idx = CH_RX;
+	uint16_t pml, data_size;
+
+	/* Read PML (2 bytes) */
+	ret = i2c_master_recv(dev->client, msg, 2);
+	if (ret <= 0) {
+		pr_err("Failed to receive PML\n");
+		return;
+	}
+
+	pml = (msg[0] << 8) | msg[1];
+	if (!pml)
+		return;
+
+	data_size = pml + 2;
+
+	/* Read the whole message, including PML */
+	ret = i2c_master_recv(dev->client, msg, data_size);
+	if (ret <= 0) {
+		pr_err("Failed to receive a Port Message\n");
+		return;
+	}
+
+	for (;;) {
+		/* Conditions to wait for: poisoned channel or free buffer
+		   available for reading  */
+		if (wait_event_interruptible(dev->rx.waitq,
+					     !dev->is_open[ch_idx] ||
+					     !list_empty(&dev->rx.list))) {
+			pr_err("wait_event_interruptible() failed\n");
+			return;
+		}
+
+		if (!dev->is_open[ch_idx])
+			return;
+
+		mutex_lock(&dev->rx.list_mutex);
+
+		/* list may be empty if poison or remove is called */
+		if (!list_empty(&dev->rx.list))
+			break;
+
+		mutex_unlock(&dev->rx.list_mutex);
+	}
+
+	mbo = list_first_mbo(&dev->rx.list);
+	list_del(&mbo->list);
+	mutex_unlock(&dev->rx.list_mutex);
+
+	mbo->processed_length = min(data_size, mbo->buffer_length);
+	memcpy(mbo->virt_address, msg, mbo->processed_length);
+	mbo->status = MBO_SUCCESS;
+	mbo->complete(mbo);
+}
+
+/**
+ * pending_rx_work - Read pending messages through I2C
+ * @work: definition of this work item
+ *
+ * Invoked by the Interrupt Service Routine, most_irq_handler()
+ */
+static void pending_rx_work(struct work_struct *work)
+{
+	struct hdm_i2c *dev = container_of(work, struct hdm_i2c, rx.dwork.work);
+
+	do_rx_work(dev);
+
+	if (dev->polling_mode) {
+		if (dev->is_open[CH_RX])
+			schedule_delayed_work(&dev->rx.dwork,
+					      msecs_to_jiffies(MSEC_PER_SEC
+							       / scan_rate));
+	} else
+		enable_irq(dev->client->irq);
+}
+
+/*
+ * most_irq_handler - Interrupt Service Routine
+ * @irq: irq number
+ * @_dev: private data
+ *
+ * Schedules a delayed work
+ *
+ * By default the interrupt line behavior is Active Low. Once an interrupt is
+ * generated by the device, until driver clears the interrupt (by reading
+ * the PMP message), device keeps the interrupt line in low state. Since i2c
+ * read is done in work queue, the interrupt line must be disabled temporarily
+ * to avoid ISR being called repeatedly. Re-enable the interrupt in workqueue,
+ * after reading the message.
+ *
+ * Note: If we use the interrupt line in Falling edge mode, there is a
+ * possibility to miss interrupts when ISR is getting executed.
+ *
+ */
+static irqreturn_t most_irq_handler(int irq, void *_dev)
+{
+	struct hdm_i2c *dev = _dev;
+
+	disable_irq_nosync(irq);
+
+	schedule_delayed_work(&dev->rx.dwork, 0);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * i2c_probe - i2c probe handler
+ * @client: i2c client device structure
+ * @id: i2c client device id
+ *
+ * Return 0 on success, negative on failure.
+ *
+ * Register the i2c client device as a MOST interface
+ */
+static int i2c_probe(struct i2c_client *client, const struct i2c_device_id *id)
+{
+	struct hdm_i2c *dev;
+	int ret, i;
+	struct kobject *kobj;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return -ENOMEM;
+
+	/* ID format: i2c-<bus>-<address> */
+	snprintf(dev->name, sizeof(dev->name), "i2c-%d-%04x",
+		 client->adapter->nr, client->addr);
+
+	for (i = 0; i < NUM_CHANNELS; i++) {
+		dev->is_open[i] = false;
+		dev->capabilities[i].data_type = MOST_CH_CONTROL;
+		dev->capabilities[i].num_buffers_packet = MAX_BUFFERS_CONTROL;
+		dev->capabilities[i].buffer_size_packet = MAX_BUF_SIZE_CONTROL;
+	}
+	dev->capabilities[CH_RX].direction = MOST_CH_RX;
+	dev->capabilities[CH_RX].name_suffix = "rx";
+	dev->capabilities[CH_TX].direction = MOST_CH_TX;
+	dev->capabilities[CH_TX].name_suffix = "tx";
+
+	dev->most_iface.interface = ITYPE_I2C;
+	dev->most_iface.description = dev->name;
+	dev->most_iface.num_channels = NUM_CHANNELS;
+	dev->most_iface.channel_vector = dev->capabilities;
+	dev->most_iface.configure = configure_channel;
+	dev->most_iface.enqueue = enqueue;
+	dev->most_iface.poison_channel = poison_channel;
+	dev->most_iface.request_netinfo = request_netinfo;
+
+	INIT_LIST_HEAD(&dev->rx.list);
+	mutex_init(&dev->rx.list_mutex);
+	init_waitqueue_head(&dev->rx.waitq);
+
+	INIT_DELAYED_WORK(&dev->rx.dwork, pending_rx_work);
+
+	dev->client = client;
+	i2c_set_clientdata(client, dev);
+
+	kobj = most_register_interface(&dev->most_iface);
+	if (IS_ERR(kobj)) {
+		pr_err("Failed to register i2c as a MOST interface\n");
+		kfree(dev);
+		return PTR_ERR(kobj);
+	}
+
+	dev->polling_mode = polling_req || client->irq <= 0;
+	if (!dev->polling_mode) {
+		pr_info("Requesting IRQ: %d\n", client->irq);
+		ret = request_irq(client->irq, most_irq_handler, IRQF_SHARED,
+				  client->name, dev);
+		if (ret) {
+			pr_info("IRQ request failed: %d, "
+				"falling back to polling\n", ret);
+			dev->polling_mode = true;
+		}
+	}
+
+	if (dev->polling_mode)
+		pr_info("Using polling at rate: %d times/sec\n", scan_rate);
+
+	return 0;
+}
+
+/*
+ * i2c_remove - i2c remove handler
+ * @client: i2c client device structure
+ *
+ * Return 0 on success.
+ *
+ * Unregister the i2c client device as a MOST interface
+ */
+static int i2c_remove(struct i2c_client *client)
+{
+	struct hdm_i2c *dev = i2c_get_clientdata(client);
+	int i;
+
+	if (!dev->polling_mode)
+		free_irq(client->irq, dev);
+
+	most_deregister_interface(&dev->most_iface);
+
+	for (i = 0 ; i < NUM_CHANNELS; i++)
+		if (dev->is_open[i])
+			poison_channel(&dev->most_iface, i);
+	cancel_delayed_work_sync(&dev->rx.dwork);
+	kfree(dev);
+
+	return 0;
+}
+
+static const struct i2c_device_id i2c_id[] = {
+	{ "most_i2c", 0 },
+	{ }, /* Terminating entry */
+};
+
+MODULE_DEVICE_TABLE(i2c, i2c_id);
+
+static struct i2c_driver i2c_driver = {
+	.driver = {
+		.name = "hdm_i2c",
+		.owner = THIS_MODULE,
+	},
+	.probe = i2c_probe,
+	.remove = i2c_remove,
+	.id_table = i2c_id,
+};
+
+/**
+ * hdm_i2c_init - Driver Registration Routine
+ */
+static int __init hdm_i2c_init(void)
+{
+	pr_info("hdm_i2c_init()\n");
+
+	return i2c_add_driver(&i2c_driver);
+}
+
+/**
+ * hdm_i2c_exit - Driver Cleanup Routine
+ **/
+static void __exit hdm_i2c_exit(void)
+{
+	i2c_del_driver(&i2c_driver);
+	pr_info("hdm_i2c_exit()\n");
+}
+
+module_init(hdm_i2c_init);
+module_exit(hdm_i2c_exit);
+
+MODULE_AUTHOR("Jain Roy Ambi <JainRoy.Ambi@microchip.com>");
+MODULE_AUTHOR("Andrey Shvetsov <andrey.shvetsov@k2l.de>");
+MODULE_DESCRIPTION("I2C Hardware Dependent Module");
+MODULE_LICENSE("GPL");