mailbox: Introduce framework for mailbox
Introduce common framework for client/protocol drivers and
controller drivers of Inter-Processor-Communication (IPC).
Client driver developers should have a look at
include/linux/mailbox_client.h to understand the part of
the API exposed to client drivers.
Similarly controller driver developers should have a look
at include/linux/mailbox_controller.h
Reviewed-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
diff --git a/include/linux/mailbox_controller.h b/include/linux/mailbox_controller.h
new file mode 100644
index 0000000..d4cf96f
--- /dev/null
+++ b/include/linux/mailbox_controller.h
@@ -0,0 +1,133 @@
+/*
+ * 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.
+ */
+
+#ifndef __MAILBOX_CONTROLLER_H
+#define __MAILBOX_CONTROLLER_H
+
+#include <linux/of.h>
+#include <linux/types.h>
+#include <linux/timer.h>
+#include <linux/device.h>
+#include <linux/completion.h>
+
+struct mbox_chan;
+
+/**
+ * struct mbox_chan_ops - methods to control mailbox channels
+ * @send_data: The API asks the MBOX controller driver, in atomic
+ * context try to transmit a message on the bus. Returns 0 if
+ * data is accepted for transmission, -EBUSY while rejecting
+ * if the remote hasn't yet read the last data sent. Actual
+ * transmission of data is reported by the controller via
+ * mbox_chan_txdone (if it has some TX ACK irq). It must not
+ * sleep.
+ * @startup: Called when a client requests the chan. The controller
+ * could ask clients for additional parameters of communication
+ * to be provided via client's chan_data. This call may
+ * block. After this call the Controller must forward any
+ * data received on the chan by calling mbox_chan_received_data.
+ * The controller may do stuff that need to sleep.
+ * @shutdown: Called when a client relinquishes control of a chan.
+ * This call may block too. The controller must not forward
+ * any received data anymore.
+ * The controller may do stuff that need to sleep.
+ * @last_tx_done: If the controller sets 'txdone_poll', the API calls
+ * this to poll status of last TX. The controller must
+ * give priority to IRQ method over polling and never
+ * set both txdone_poll and txdone_irq. Only in polling
+ * mode 'send_data' is expected to return -EBUSY.
+ * The controller may do stuff that need to sleep/block.
+ * Used only if txdone_poll:=true && txdone_irq:=false
+ * @peek_data: Atomic check for any received data. Return true if controller
+ * has some data to push to the client. False otherwise.
+ */
+struct mbox_chan_ops {
+ int (*send_data)(struct mbox_chan *chan, void *data);
+ int (*startup)(struct mbox_chan *chan);
+ void (*shutdown)(struct mbox_chan *chan);
+ bool (*last_tx_done)(struct mbox_chan *chan);
+ bool (*peek_data)(struct mbox_chan *chan);
+};
+
+/**
+ * struct mbox_controller - Controller of a class of communication channels
+ * @dev: Device backing this controller
+ * @ops: Operators that work on each communication chan
+ * @chans: Array of channels
+ * @num_chans: Number of channels in the 'chans' array.
+ * @txdone_irq: Indicates if the controller can report to API when
+ * the last transmitted data was read by the remote.
+ * Eg, if it has some TX ACK irq.
+ * @txdone_poll: If the controller can read but not report the TX
+ * done. Ex, some register shows the TX status but
+ * no interrupt rises. Ignored if 'txdone_irq' is set.
+ * @txpoll_period: If 'txdone_poll' is in effect, the API polls for
+ * last TX's status after these many millisecs
+ * @of_xlate: Controller driver specific mapping of channel via DT
+ * @poll: API private. Used to poll for TXDONE on all channels.
+ * @node: API private. To hook into list of controllers.
+ */
+struct mbox_controller {
+ struct device *dev;
+ struct mbox_chan_ops *ops;
+ struct mbox_chan *chans;
+ int num_chans;
+ bool txdone_irq;
+ bool txdone_poll;
+ unsigned txpoll_period;
+ struct mbox_chan *(*of_xlate)(struct mbox_controller *mbox,
+ const struct of_phandle_args *sp);
+ /* Internal to API */
+ struct timer_list poll;
+ struct list_head node;
+};
+
+/*
+ * 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 transfer 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.
+ * REVISIT: 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
+
+/**
+ * struct mbox_chan - s/w representation of a communication chan
+ * @mbox: Pointer to the parent/provider of this channel
+ * @txdone_method: Way to detect TXDone chosen by the API
+ * @cl: Pointer to the current owner of this channel
+ * @tx_complete: Transmission completion
+ * @active_req: Currently active request hook
+ * @msg_count: No. of mssg currently queued
+ * @msg_free: Index of next available mssg slot
+ * @msg_data: Hook for data packet
+ * @lock: Serialise access to the channel
+ * @con_priv: Hook for controller driver to attach private data
+ */
+struct mbox_chan {
+ struct mbox_controller *mbox;
+ unsigned txdone_method;
+ struct mbox_client *cl;
+ struct completion tx_complete;
+ void *active_req;
+ unsigned msg_count, msg_free;
+ void *msg_data[MBOX_TX_QUEUE_LEN];
+ spinlock_t lock; /* Serialise access to the channel */
+ void *con_priv;
+};
+
+int mbox_controller_register(struct mbox_controller *mbox); /* can sleep */
+void mbox_controller_unregister(struct mbox_controller *mbox); /* can sleep */
+void mbox_chan_received_data(struct mbox_chan *chan, void *data); /* atomic */
+void mbox_chan_txdone(struct mbox_chan *chan, int r); /* atomic */
+
+#endif /* __MAILBOX_CONTROLLER_H */