1/* SPDX-License-Identifier: GPL-2.0-only */
2
3#ifndef __MAILBOX_CONTROLLER_H
4#define __MAILBOX_CONTROLLER_H
5
6#include <linux/of.h>
7#include <linux/types.h>
8#include <linux/hrtimer.h>
9#include <linux/device.h>
10#include <linux/completion.h>
11
12struct mbox_chan;
13
14/**
15 * struct mbox_chan_ops - methods to control mailbox channels
16 * @send_data:	The API asks the MBOX controller driver, in atomic
17 *		context try to transmit a message on the bus. Returns 0 if
18 *		data is accepted for transmission, -EBUSY while rejecting
19 *		if the remote hasn't yet read the last data sent. Actual
20 *		transmission of data is reported by the controller via
21 *		mbox_chan_txdone (if it has some TX ACK irq). It must not
22 *		sleep.
23 * @flush:	Called when a client requests transmissions to be blocking but
24 *		the context doesn't allow sleeping. Typically the controller
25 *		will implement a busy loop waiting for the data to flush out.
26 * @startup:	Called when a client requests the chan. The controller
27 *		could ask clients for additional parameters of communication
28 *		to be provided via client's chan_data. This call may
29 *		block. After this call the Controller must forward any
30 *		data received on the chan by calling mbox_chan_received_data.
31 *		The controller may do stuff that need to sleep.
32 * @shutdown:	Called when a client relinquishes control of a chan.
33 *		This call may block too. The controller must not forward
34 *		any received data anymore.
35 *		The controller may do stuff that need to sleep.
36 * @last_tx_done: If the controller sets 'txdone_poll', the API calls
37 *		  this to poll status of last TX. The controller must
38 *		  give priority to IRQ method over polling and never
39 *		  set both txdone_poll and txdone_irq. Only in polling
40 *		  mode 'send_data' is expected to return -EBUSY.
41 *		  The controller may do stuff that need to sleep/block.
42 *		  Used only if txdone_poll:=true && txdone_irq:=false
43 * @peek_data: Atomic check for any received data. Return true if controller
44 *		  has some data to push to the client. False otherwise.
45 */
46struct mbox_chan_ops {
47	int (*send_data)(struct mbox_chan *chan, void *data);
48	int (*flush)(struct mbox_chan *chan, unsigned long timeout);
49	int (*startup)(struct mbox_chan *chan);
50	void (*shutdown)(struct mbox_chan *chan);
51	bool (*last_tx_done)(struct mbox_chan *chan);
52	bool (*peek_data)(struct mbox_chan *chan);
53};
54
55/**
56 * struct mbox_controller - Controller of a class of communication channels
57 * @dev:		Device backing this controller
58 * @ops:		Operators that work on each communication chan
59 * @chans:		Array of channels
60 * @num_chans:		Number of channels in the 'chans' array.
61 * @txdone_irq:		Indicates if the controller can report to API when
62 *			the last transmitted data was read by the remote.
63 *			Eg, if it has some TX ACK irq.
64 * @txdone_poll:	If the controller can read but not report the TX
65 *			done. Ex, some register shows the TX status but
66 *			no interrupt rises. Ignored if 'txdone_irq' is set.
67 * @txpoll_period:	If 'txdone_poll' is in effect, the API polls for
68 *			last TX's status after these many millisecs
69 * @of_xlate:		Controller driver specific mapping of channel via DT
70 * @poll_hrt:		API private. hrtimer used to poll for TXDONE on all
71 *			channels.
72 * @node:		API private. To hook into list of controllers.
73 */
74struct mbox_controller {
75	struct device *dev;
76	const struct mbox_chan_ops *ops;
77	struct mbox_chan *chans;
78	int num_chans;
79	bool txdone_irq;
80	bool txdone_poll;
81	unsigned txpoll_period;
82	struct mbox_chan *(*of_xlate)(struct mbox_controller *mbox,
83				      const struct of_phandle_args *sp);
84	/* Internal to API */
85	struct hrtimer poll_hrt;
86	spinlock_t poll_hrt_lock;
87	struct list_head node;
88};
89
90/*
91 * The length of circular buffer for queuing messages from a client.
92 * 'msg_count' tracks the number of buffered messages while 'msg_free'
93 * is the index where the next message would be buffered.
94 * We shouldn't need it too big because every transfer is interrupt
95 * triggered and if we have lots of data to transfer, the interrupt
96 * latencies are going to be the bottleneck, not the buffer length.
97 * Besides, mbox_send_message could be called from atomic context and
98 * the client could also queue another message from the notifier 'tx_done'
99 * of the last transfer done.
100 * REVISIT: If too many platforms see the "Try increasing MBOX_TX_QUEUE_LEN"
101 * print, it needs to be taken from config option or somesuch.
102 */
103#define MBOX_TX_QUEUE_LEN	20
104
105/**
106 * struct mbox_chan - s/w representation of a communication chan
107 * @mbox:		Pointer to the parent/provider of this channel
108 * @txdone_method:	Way to detect TXDone chosen by the API
109 * @cl:			Pointer to the current owner of this channel
110 * @tx_complete:	Transmission completion
111 * @active_req:		Currently active request hook
112 * @msg_count:		No. of mssg currently queued
113 * @msg_free:		Index of next available mssg slot
114 * @msg_data:		Hook for data packet
115 * @lock:		Serialise access to the channel
116 * @con_priv:		Hook for controller driver to attach private data
117 */
118struct mbox_chan {
119	struct mbox_controller *mbox;
120	unsigned txdone_method;
121	struct mbox_client *cl;
122	struct completion tx_complete;
123	void *active_req;
124	unsigned msg_count, msg_free;
125	void *msg_data[MBOX_TX_QUEUE_LEN];
126	spinlock_t lock; /* Serialise access to the channel */
127	void *con_priv;
128};
129
130int mbox_controller_register(struct mbox_controller *mbox); /* can sleep */
131void mbox_controller_unregister(struct mbox_controller *mbox); /* can sleep */
132void mbox_chan_received_data(struct mbox_chan *chan, void *data); /* atomic */
133void mbox_chan_txdone(struct mbox_chan *chan, int r); /* atomic */
134
135int devm_mbox_controller_register(struct device *dev,
136				  struct mbox_controller *mbox);
137void devm_mbox_controller_unregister(struct device *dev,
138				     struct mbox_controller *mbox);
139
140#endif /* __MAILBOX_CONTROLLER_H */
141