1 /* SPDX-License-Identifier: GPL-2.0 */
3 * Copyright (c) 2016, NVIDIA CORPORATION.
10 * A mailbox is a hardware mechanism for transferring small fixed-size messages
11 * and/or notifications between the CPU on which U-Boot runs and some other
12 * device such as an auxiliary CPU running firmware or a hardware module.
14 * Data transfer is optional; a mailbox may consist solely of a notification
15 * mechanism. When data transfer is implemented, it is via HW registers or
16 * FIFOs, rather than via RAM-based buffers. The mailbox API generally
17 * implements any communication protocol enforced solely by hardware, and
18 * leaves any higher-level protocols to other layers.
20 * A mailbox channel is a bi-directional mechanism that can send a message or
21 * notification to a single specific remote entity, and receive messages or
22 * notifications from that entity. The size, content, and format of such
23 * messages is defined by the mailbox implementation, or the remote entity with
24 * which it communicates; there is no general standard at this API level.
26 * A driver that implements UCLASS_MAILBOX is a mailbox provider. A provider
27 * will often implement multiple separate mailbox channels, since the hardware
28 * it manages often has this capability. mailbox-uclass.h describes the
29 * interface which mailbox providers must implement.
31 * Mailbox consumers/clients generate and send, or receive and process,
32 * messages. This header file describes the API used by clients.
38 * struct mbox_chan - A handle to a single mailbox channel.
40 * Clients provide storage for channels. The content of the channel structure
41 * is managed solely by the mailbox API and mailbox drivers. A mailbox channel
42 * is initialized by "get"ing the mailbox. The channel struct is passed to all
43 * other mailbox APIs to identify which mailbox to operate upon.
45 * @dev: The device which implements the mailbox.
46 * @id: The mailbox channel ID within the provider.
48 * Currently, the mailbox API assumes that a single integer ID is enough to
49 * identify and configure any mailbox channel for any mailbox provider. If this
50 * assumption becomes invalid in the future, the struct could be expanded to
51 * either (a) add more fields to allow mailbox providers to store additional
52 * information, or (b) replace the id field with an opaque pointer, which the
53 * provider would dynamically allocated during its .of_xlate op, and process
54 * during is .request op. This may require the addition of an extra op to clean
60 * Written by of_xlate. We assume a single id is enough for now. In the
61 * future, we might add more fields here.
67 * mbox_get_by_index - Get/request a mailbox by integer index
69 * This looks up and requests a mailbox channel. The index is relative to the
70 * client device; each device is assumed to have n mailbox channels associated
71 * with it somehow, and this function finds and requests one of them. The
72 * mapping of client device channel indices to provider channels may be via
73 * device-tree properties, board-provided mapping tables, or some other
76 * @dev: The client device.
77 * @index: The index of the mailbox channel to request, within the
78 * client's list of channels.
79 * @chan A pointer to a channel object to initialize.
80 * @return 0 if OK, or a negative error code.
82 int mbox_get_by_index(struct udevice *dev, int index, struct mbox_chan *chan);
85 * mbox_get_by_name - Get/request a mailbox by name
87 * This looks up and requests a mailbox channel. The name is relative to the
88 * client device; each device is assumed to have n mailbox channels associated
89 * with it somehow, and this function finds and requests one of them. The
90 * mapping of client device channel names to provider channels may be via
91 * device-tree properties, board-provided mapping tables, or some other
94 * @dev: The client device.
95 * @name: The name of the mailbox channel to request, within the client's
97 * @chan A pointer to a channel object to initialize.
98 * @return 0 if OK, or a negative error code.
100 int mbox_get_by_name(struct udevice *dev, const char *name,
101 struct mbox_chan *chan);
104 * mbox_free - Free a previously requested mailbox channel.
106 * @chan: A channel object that was previously successfully requested by
107 * calling mbox_get_by_*().
108 * @return 0 if OK, or a negative error code.
110 int mbox_free(struct mbox_chan *chan);
113 * mbox_send - Send a message over a mailbox channel
115 * This function will send a message to the remote entity. It may return before
116 * the remote entity has received and/or processed the message.
118 * @chan: A channel object that was previously successfully requested by
119 * calling mbox_get_by_*().
120 * @data: A pointer to the message to transfer. The format and size of
121 * the memory region pointed at by @data is determined by the
122 * mailbox provider. Providers that solely transfer notifications
123 * will ignore this parameter.
124 * @return 0 if OK, or a negative error code.
126 int mbox_send(struct mbox_chan *chan, const void *data);
129 * mbox_recv - Receive any available message from a mailbox channel
131 * This function will wait (up to the specified @timeout_us) for a message to
132 * be sent by the remote entity, and write the content of any such message
133 * into a caller-provided buffer.
135 * @chan: A channel object that was previously successfully requested by
136 * calling mbox_get_by_*().
137 * @data: A pointer to the buffer to receive the message. The format and
138 * size of the memory region pointed at by @data is determined by
139 * the mailbox provider. Providers that solely transfer
140 * notifications will ignore this parameter.
141 * @timeout_us: The maximum time to wait for a message to be available, in
142 * micro-seconds. A value of 0 does not wait at all.
143 * @return 0 if OK, -ENODATA if no message was available, or a negative error
146 int mbox_recv(struct mbox_chan *chan, void *data, ulong timeout_us);