Date:	Fri, 28 Mar 2014 15:08:11 -0700
From:	Markus Mayer <markus.mayer@...aro.org>
To:	Linux Kernel Mailing list <linux-kernel@...r.kernel.org>,
	Jassi Brar <jassisinghbrar@...il.com>
CC:	<gregkh@...uxfoundation.org>, <s-anna@...com>, <tony@...mide.com>,
	<omar.ramirez@...itl.com>, <loic.pallardy@...com>,
	<lftan.linux@...il.com>, <slapdau@...oo.com.au>,
	<courtney.cavin@...ymobile.com>, <rafael.j.wysocki@...el.com>,
	<robherring2@...il.com>, <arnd@...db.de>, <joshc@...eaurora.org>,
	<linus.walleij@...aro.org>, <galak@...eaurora.org>,
	<ks.giri@...sung.com>
Subject: Re: [PATCHv4,2/5] mailbox: Introduce framework for mailbox

> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
> new file mode 100644
> index 0000000..79d576e
> --- /dev/null
> +++ b/drivers/mailbox/mailbox.c
> @@ -0,0 +1,589 @@
> +/*
> + * Mailbox: Common code for Mailbox controllers and users
> + *
> + * Copyright (C) 2014 Linaro Ltd.
> + * Author: Jassi Brar <jassisinghbrar@...il.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/interrupt.h>
> +#include <linux/spinlock.h>
> +#include <linux/mutex.h>
> +#include <linux/delay.h>
> +#include <linux/slab.h>
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/mailbox_client.h>
> +#include <linux/mailbox_controller.h>
> +
> +/*
> + * The length of circular buffer for queuing messages from a client.
> + * 'msg_count' tracks the number of buffered messages while 'msg_free'
> + * is the index where the next message would be buffered.
> + * We shouldn't need it too big because every transferr is interrupt
> + * triggered and if we have lots of data to transfer, the interrupt
> + * latencies are going to be the bottleneck, not the buffer length.
> + * Besides, mbox_send_message could be called from atomic context and
> + * the client could also queue another message from the notifier 'tx_done'
> + * of the last transfer done.
> + * REVIST: If too many platforms see the "Try increasing MBOX_TX_QUEUE_LEN"
> + * print, it needs to be taken from config option or somesuch.
> + */
> +#define MBOX_TX_QUEUE_LEN	20
> +
> +#define TXDONE_BY_IRQ	(1 << 0) /* controller has remote RTR irq */
> +#define TXDONE_BY_POLL	(1 << 1) /* controller can read status of last TX */
> +#define TXDONE_BY_ACK	(1 << 2) /* S/W ACK recevied by Client ticks the TX */
> +
> +struct mbox_chan {
> +	char name[16]; /* Physical link's name */
> +	struct mbox_con *con; /* Parent Controller */
> +	unsigned txdone_method;
> +
> +	/* Physical links */
> +	struct mbox_link *link;
> +	struct mbox_link_ops *link_ops;
> +
> +	/* client */
> +	struct mbox_client *cl;
> +	struct completion tx_complete;
> +
> +	void *active_req;
> +	unsigned msg_count, msg_free;
> +	void *msg_data[MBOX_TX_QUEUE_LEN];
> +	/* Access to the channel */
> +	spinlock_t lock;
> +	/* Hook to add to the controller's list of channels */
> +	struct list_head node;
> +	/* Notifier to all clients waiting on aquiring this channel */
> +	struct blocking_notifier_head avail;
> +} __aligned(32);
> +
> +/* Internal representation of a controller */
> +struct mbox_con {
> +	struct device *dev;
> +	char name[16]; /* controller_name */
> +	struct list_head channels;
> +	/*
> +	 * If the controller supports only TXDONE_BY_POLL,
> +	 * this timer polls all the links for txdone.
> +	 */
> +	struct timer_list poll;
> +	unsigned period;
> +	/* Hook to add to the global controller list */
> +	struct list_head node;
> +} __aligned(32);
> +
> +static LIST_HEAD(mbox_cons);
> +static DEFINE_MUTEX(con_mutex);
> +
> +static int _add_to_rbuf(struct mbox_chan *chan, void *mssg)
> +{
> +	int idx;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&chan->lock, flags);
> +
> +	/* See if there is any space left */
> +	if (chan->msg_count == MBOX_TX_QUEUE_LEN) {
> +		spin_unlock_irqrestore(&chan->lock, flags);
> +		return -ENOMEM;
> +	}
> +
> +	idx = chan->msg_free;
> +	chan->msg_data[idx] = mssg;
> +	chan->msg_count++;
> +
> +	if (idx == MBOX_TX_QUEUE_LEN - 1)
> +		chan->msg_free = 0;
> +	else
> +		chan->msg_free++;
> +
> +	spin_unlock_irqrestore(&chan->lock, flags);
> +
> +	return idx;
> +}
> +
> +static void _msg_submit(struct mbox_chan *chan)
> +{
> +	struct mbox_link *link = chan->link;
> +	unsigned count, idx;
> +	unsigned long flags;
> +	void *data;
> +	int err;
> +
> +	spin_lock_irqsave(&chan->lock, flags);
> +
> +	if (!chan->msg_count || chan->active_req) {
> +		spin_unlock_irqrestore(&chan->lock, flags);
> +		return;
> +	}
> +
> +	count = chan->msg_count;
> +	idx = chan->msg_free;
> +	if (idx >= count)
> +		idx -= count;
> +	else
> +		idx += MBOX_TX_QUEUE_LEN - count;
> +
> +	data = chan->msg_data[idx];
> +
> +	/* Try to submit a message to the MBOX controller */
> +	err = chan->link_ops->send_data(link, data);
> +	if (!err) {
> +		chan->active_req = data;
> +		chan->msg_count--;
> +	}
> +
> +	spin_unlock_irqrestore(&chan->lock, flags);
> +}
> +
> +static void tx_tick(struct mbox_chan *chan, enum mbox_result r)
> +{
> +	unsigned long flags;
> +	void *mssg;
> +
> +	spin_lock_irqsave(&chan->lock, flags);
> +	mssg = chan->active_req;
> +	chan->active_req = NULL;
> +	spin_unlock_irqrestore(&chan->lock, flags);
> +
> +	/* Submit next message */
> +	_msg_submit(chan);
> +
> +	/* Notify the client */
> +	if (chan->cl->tx_block)
> +		complete(&chan->tx_complete);
> +	else if (mssg && chan->cl->tx_done)
> +		chan->cl->tx_done(chan->cl, mssg, r);
> +}
> +
> +static void poll_txdone(unsigned long data)
> +{
> +	struct mbox_con *con = (struct mbox_con *)data;
> +	bool txdone, resched = false;
> +	struct mbox_chan *chan;
> +
> +	list_for_each_entry(chan, &con->channels, node) {
> +		if (chan->active_req && chan->cl) {
> +			resched = true;
> +			txdone = chan->link_ops->last_tx_done(chan->link);
> +			if (txdone)
> +				tx_tick(chan, MBOX_OK);
> +		}
> +	}
> +
> +	if (resched)
> +		mod_timer(&con->poll,
> +			jiffies + msecs_to_jiffies(con->period));
> +}
> +
> +/**
> + * mbox_link_received_data - A way for controller driver to push data
> + *				received from remote to the upper layer.
> + * @link: Pointer to the mailbox link on which RX happened.
> + * @data: Client specific message typecasted as void *
> + *
> + * After startup and before shutdown any data received on the link
> + * is passed on to the API via atomic mbox_link_received_data().
> + * The controller should ACK the RX only after this call returns.
> + */
> +void mbox_link_received_data(struct mbox_link *link, void *mssg)
> +{
> +	struct mbox_chan *chan = (struct mbox_chan *)link->api_priv;
> +
> +	/* No buffering the received data */
> +	if (chan->cl->rx_callback)
> +		chan->cl->rx_callback(chan->cl, mssg);
> +}
> +EXPORT_SYMBOL_GPL(mbox_link_received_data);
> +
> +/**
> + * mbox_link_txdone - A way for controller driver to notify the
> + *			framework that the last TX has completed.
> + * @link: Pointer to the mailbox link on which TX happened.
> + * @r: Status of last TX - OK or ERROR
> + *
> + * The controller that has IRQ for TX ACK calls this atomic API
> + * to tick the TX state machine. It works only if txdone_irq
> + * is set by the controller.
> + */
> +void mbox_link_txdone(struct mbox_link *link, enum mbox_result r)
> +{
> +	struct mbox_chan *chan = (struct mbox_chan *)link->api_priv;
> +
> +	if (unlikely(!(chan->txdone_method & TXDONE_BY_IRQ))) {
> +		pr_err("Controller can't run the TX ticker\n");
> +		return;
> +	}
> +
> +	tx_tick(chan, r);
> +}
> +EXPORT_SYMBOL_GPL(mbox_link_txdone);
> +
> +/**
> + * mbox_client_txdone - The way for a client to run the TX state machine.
> + * @chan: Mailbox channel assigned to this client.
> + * @r: Success status of last transmission.
> + *
> + * The client/protocol had received some 'ACK' packet and it notifies
> + * the API that the last packet was sent successfully. This only works
> + * if the controller can't sense TX-Done.
> + */
> +void mbox_client_txdone(struct mbox_chan *chan, enum mbox_result r)
> +{
> +	if (unlikely(!(chan->txdone_method & TXDONE_BY_ACK))) {
> +		pr_err("Client can't run the TX ticker\n");
> +		return;
> +	}
> +
> +	tx_tick(chan, r);
> +}
> +EXPORT_SYMBOL_GPL(mbox_client_txdone);
> +
> +/**
> + * mbox_send_message -	For client to submit a message to be
> + *				sent to the remote.
> + * @chan: Mailbox channel assigned to this client.
> + * @mssg: Client specific message typecasted.
> + *
> + * For client to submit data to the controller destined for a remote
> + * processor. If the client had set 'tx_block', the call will return
> + * either when the remote receives the data or when 'tx_tout' millisecs
> + * run out.
> + *  In non-blocking mode, the requests are buffered by the API and a
> + * non-negative token is returned for each queued request. If the request
> + * is not queued, a negative token is returned. Upon failure or successful
> + * TX, the API calls 'tx_done' from atomic context, from which the client
> + * could submit yet another request.
> + *  In blocking mode, 'tx_done' is not called, effectively making the
> + * queue length 1.
> + * The pointer to message should be preserved until it is sent
> + * over the link, i.e, tx_done() is made.
> + * This function could be called from atomic context as it simply
> + * queues the data and returns a token against the request.
> + *
> + * Return: Non-negative integer for successful submission (non-blocking mode)
> + *	or transmission over link (blocking mode).
> + *	Negative value denotes failure.
> + */
> +int mbox_send_message(struct mbox_chan *chan, void *mssg)
> +{
> +	int t;
> +
> +	if (!chan || !chan->cl)
> +		return -EINVAL;
> +
> +	t = _add_to_rbuf(chan, mssg);
> +	if (t < 0) {
> +		pr_err("Try increasing MBOX_TX_QUEUE_LEN\n");
> +		return t;
> +	}
> +
> +	_msg_submit(chan);
> +
> +	if (chan->txdone_method	== TXDONE_BY_POLL)
> +		poll_txdone((unsigned long)chan->con);

Wouldn't it be cleaner to use
		poll_txdone((unsigned long)&chan->con);
?

> +
> +	if (chan->cl->tx_block && chan->active_req) {
> +		int ret;
> +		init_completion(&chan->tx_complete);
> +		ret = wait_for_completion_timeout(&chan->tx_complete,
> +			chan->cl->tx_tout);
> +		if (ret == 0) {
> +			t = -EIO;
> +			tx_tick(chan, MBOX_ERR);
> +		}
> +	}
> +
> +	return t;
> +}
> +EXPORT_SYMBOL_GPL(mbox_send_message);
> +
> +/**
> + * mbox_request_channel - Request a mailbox channel.
> + * @cl: Identity of the client requesting the channel.
> + *
> + * The Client specifies its requirements and capabilities while asking for
> + * a mailbox channel by name. It can't be called from atomic context.
> + * The channel is exclusively allocated and can't be used by another
> + * client before the owner calls mbox_free_channel.
> + * After assignment, any packet received on this channel will be
> + * handed over to the client via the 'rx_callback'.
> + *
> + * Return: Pointer to the channel assigned to the client if successful.
> + *		ERR_PTR for request failure.
> + */
> +struct mbox_chan *mbox_request_channel(struct mbox_client *cl)
> +{
> +	struct mbox_chan *chan;
> +	struct mbox_con *con;
> +	unsigned long flags;
> +	char *con_name;
> +	int len, ret;
> +
> +	con_name = cl->chan_name;
> +	len = strcspn(cl->chan_name, ":");
> +
> +	ret = 0;
> +	mutex_lock(&con_mutex);
> +	list_for_each_entry(con, &mbox_cons, node)
> +		if (!strncmp(con->name, con_name, len)) {
> +			ret = 1;
> +			break;
> +		}
> +	mutex_unlock(&con_mutex);
> +
> +	if (!ret) {
> +		pr_info("Channel(%s) not found!\n", cl->chan_name);
> +		return ERR_PTR(-ENODEV);
> +	}
> +
> +	ret = 0;
> +	list_for_each_entry(chan, &con->channels, node) {
> +		if (!chan->cl &&
> +				!strcmp(con_name + len + 1, chan->name) &&
> +				try_module_get(con->dev->driver->owner)) {
> +			spin_lock_irqsave(&chan->lock, flags);
> +			chan->msg_free = 0;
> +			chan->msg_count = 0;
> +			chan->active_req = NULL;
> +			chan->cl = cl;
> +			if (!cl->tx_tout) /* wait for ever */
> +				cl->tx_tout = msecs_to_jiffies(3600000);
> +			else
> +				cl->tx_tout = msecs_to_jiffies(cl->tx_tout);
> +			if (chan->txdone_method	== TXDONE_BY_POLL
> +					&& cl->knows_txdone)
> +				chan->txdone_method |= TXDONE_BY_ACK;
> +			spin_unlock_irqrestore(&chan->lock, flags);
> +			ret = 1;
> +			break;
> +		}
> +	}
> +
> +	if (!ret) {
> +		pr_err("Unable to assign mailbox(%s)\n", cl->chan_name);
> +		return ERR_PTR(-EBUSY);
> +	}
> +
> +	ret = chan->link_ops->startup(chan->link, cl->link_data);
> +	if (ret) {
> +		pr_err("Unable to startup the link\n");
> +		mbox_free_channel(chan);
> +		return ERR_PTR(ret);
> +	}
> +
> +	return chan;
> +}
> +EXPORT_SYMBOL_GPL(mbox_request_channel);
> +
> +/**
> + * mbox_free_channel - The client relinquishes control of a mailbox
> + *			channel by this call.
> + * @chan: The mailbox channel to be freed.
> + */
> +void mbox_free_channel(struct mbox_chan *chan)
> +{
> +	unsigned long flags;
> +
> +	if (!chan || !chan->cl)
> +		return;
> +
> +	chan->link_ops->shutdown(chan->link);
> +
> +	/* The queued TX requests are simply aborted, no callbacks are made */
> +	spin_lock_irqsave(&chan->lock, flags);
> +	chan->cl = NULL;
> +	chan->active_req = NULL;
> +	if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
> +		chan->txdone_method = TXDONE_BY_POLL;
> +
> +	module_put(chan->con->dev->driver->owner);
> +
> +	spin_unlock_irqrestore(&chan->lock, flags);
> +
> +	blocking_notifier_call_chain(&chan->avail, 0, NULL);
> +}
> +EXPORT_SYMBOL_GPL(mbox_free_channel);
> +
> +static struct mbox_chan *name_to_chan(const char *name)
> +{
> +	struct mbox_chan *chan = NULL;
> +	struct mbox_con *con;
> +	int len, found = 0;
> +
> +	len = strcspn(name, ":");
> +
> +	mutex_lock(&con_mutex);
> +
> +	list_for_each_entry(con, &mbox_cons, node) {
> +		if (!strncmp(con->name, name, len)) {
> +			list_for_each_entry(chan, &con->channels, node) {
> +				if (!strcmp(name + len + 1, chan->name)) {
> +					found = 1;
> +					goto done;
> +				}
> +			}
> +		}
> +	}
> +done:
> +	mutex_unlock(&con_mutex);
> +
> +	if (!found)
> +		return NULL;
> +
> +	return chan;
> +}
> +
> +/**
> + * mbox_notify_chan_register - The client may ask the framework to be
> + *		 notified when a particular channel becomes available
> + *		 to be acquired again.
> + * @name: Name of the mailbox channel the client is interested in.
> + * @nb:	Pointer to the notifier.
> + */
> +int mbox_notify_chan_register(const char *name, struct notifier_block *nb)
> +{
> +	struct mbox_chan *chan = name_to_chan(name);
> +
> +	if (chan && nb)
> +		return blocking_notifier_chain_register(&chan->avail, nb);
> +
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL_GPL(mbox_notify_chan_register);
> +
> +/**
> + * mbox_notify_chan_unregister - The client is no more interested in channel.
> + *
> + * @name: Name of the mailbox channel the client was interested in.
> + * @nb: Pointer to the notifier.
> + */
> +void mbox_notify_chan_unregister(const char *name, struct notifier_block *nb)
> +{
> +	struct mbox_chan *chan = name_to_chan(name);
> +
> +	if (chan && nb)
> +		blocking_notifier_chain_unregister(&chan->avail, nb);
> +}
> +EXPORT_SYMBOL_GPL(mbox_notify_chan_unregister);
> +
> +/**
> + * mbox_controller_register - Register the mailbox controller
> + * @mbox_con:	Pointer to the mailbox controller.
> + *
> + * The controller driver registers its communication links to the
> + * global pool managed by the common framework.
> + */
> +int mbox_controller_register(struct mbox_controller *mbox)
> +{
> +	int i, num_links, txdone;
> +	struct mbox_chan *chan;
> +	struct mbox_con *con;
> +
> +	/* Sanity check */
> +	if (!mbox || !mbox->ops)
> +		return -EINVAL;
> +
> +	for (i = 0; mbox->links[i]; i++)
> +		;
> +	if (!i)
> +		return -EINVAL;
> +	num_links = i;
> +
> +	mutex_lock(&con_mutex);
> +	/* Check if already populated */
> +	list_for_each_entry(con, &mbox_cons, node)
> +		if (!strcmp(mbox->controller_name, con->name)) {
> +			mutex_unlock(&con_mutex);
> +			return -EINVAL;
> +		}
> +
> +	con = kzalloc(sizeof(struct mbox_con), GFP_KERNEL);
> +	if (!con)
> +		return -ENOMEM;

The mutex is not freed here.

> +
> +	chan = kzalloc(sizeof(struct mbox_chan) * num_links, GFP_KERNEL);
> +	if (!chan) {
> +		kfree(con);
> +		return -ENOMEM;

Again, the mutex is not freed.

You could move both allocations above the mutex. Then you won't have to
worry about it.

> +	}
> +
> +	con->dev = mbox->dev;
> +	INIT_LIST_HEAD(&con->channels);
> +	snprintf(con->name, 16, "%s", mbox->controller_name);
> +
> +	if (mbox->txdone_irq)
> +		txdone = TXDONE_BY_IRQ;
> +	else if (mbox->txdone_poll)
> +		txdone = TXDONE_BY_POLL;
> +	else /* It has to be ACK then */
> +		txdone = TXDONE_BY_ACK;
> +
> +	if (txdone == TXDONE_BY_POLL) {
> +		con->period = mbox->txpoll_period;
> +		con->poll.function = &poll_txdone;
> +		con->poll.data = (unsigned long)con;

How about
		con->poll.data = (unsigned long)&con;

> +		init_timer(&con->poll);
> +	}
> +
> +	for (i = 0; i < num_links; i++) {
> +		chan[i].con = con;
> +		chan[i].cl = NULL;
> +		chan[i].link_ops = mbox->ops;
> +		chan[i].link = mbox->links[i];
> +		chan[i].txdone_method = txdone;
> +		chan[i].link->api_priv = &chan[i];
> +		spin_lock_init(&chan[i].lock);
> +		BLOCKING_INIT_NOTIFIER_HEAD(&chan[i].avail);
> +		list_add_tail(&chan[i].node, &con->channels);
> +		snprintf(chan[i].name, 16, "%s", mbox->links[i]->link_name);
> +	}
> +
> +	list_add_tail(&con->node, &mbox_cons);
> +	mutex_unlock(&con_mutex);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(mbox_controller_register);
> +
> +/**
> + * mbox_controller_unregister - UnRegister the mailbox controller
> + * @mbox_con:	Pointer to the mailbox controller.
> + *
> + * Purge the mailbox links from the global pool maintained by the framework.
> + */
> +void mbox_controller_unregister(struct mbox_controller *mbox)
> +{
> +	struct mbox_con *t, *con = NULL;
> +	struct mbox_chan *chan;
> +
> +	mutex_lock(&con_mutex);
> +
> +	list_for_each_entry(t, &mbox_cons, node)
> +		if (!strcmp(mbox->controller_name, t->name)) {
> +			con = t;
> +			break;
> +		}
> +
> +	if (con)
> +		list_del(&con->node);
> +
> +	mutex_unlock(&con_mutex);
> +
> +	if (!con)
> +		return;
> +
> +	list_for_each_entry(chan, &con->channels, node)
> +		mbox_free_channel(chan);
> +
> +	del_timer_sync(&con->poll);
> +
> +	kfree(con);
> +}
> +EXPORT_SYMBOL_GPL(mbox_controller_unregister);

Regards,
-Markus
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