1// SPDX-License-Identifier: GPL-2.0
2/*
3 * System Control and Management Interface (SCMI) Message Mailbox Transport
4 * driver.
5 *
6 * Copyright (C) 2019 ARM Ltd.
7 */
8
9#include <linux/err.h>
10#include <linux/device.h>
11#include <linux/mailbox_client.h>
12#include <linux/of.h>
13#include <linux/of_address.h>
14#include <linux/slab.h>
15
16#include "common.h"
17
18/**
19 * struct scmi_mailbox - Structure representing a SCMI mailbox transport
20 *
21 * @cl: Mailbox Client
22 * @chan: Transmit/Receive mailbox channel
23 * @cinfo: SCMI channel info
24 * @shmem: Transmit/Receive shared memory area
25 */
26struct scmi_mailbox {
27	struct mbox_client cl;
28	struct mbox_chan *chan;
29	struct scmi_chan_info *cinfo;
30	struct scmi_shared_mem __iomem *shmem;
31};
32
33#define client_to_scmi_mailbox(c) container_of(c, struct scmi_mailbox, cl)
34
35static void tx_prepare(struct mbox_client *cl, void *m)
36{
37	struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
38
39	shmem_tx_prepare(smbox->shmem, m);
40}
41
42static void rx_callback(struct mbox_client *cl, void *m)
43{
44	struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
45
46	scmi_rx_callback(smbox->cinfo, shmem_read_header(smbox->shmem));
47}
48
49static bool mailbox_chan_available(struct device *dev, int idx)
50{
51	return !of_parse_phandle_with_args(dev->of_node, "mboxes",
52					   "#mbox-cells", idx, NULL);
53}
54
55static int mailbox_chan_validate(struct device *cdev)
56{
57	int num_mb, num_sh, ret = 0;
58	struct device_node *np = cdev->of_node;
59
60	num_mb = of_count_phandle_with_args(np, "mboxes", "#mbox-cells");
61	num_sh = of_count_phandle_with_args(np, "shmem", NULL);
62	/* Bail out if mboxes and shmem descriptors are inconsistent */
63	if (num_mb <= 0 || num_sh > 2 || num_mb != num_sh) {
64		dev_warn(cdev, "Invalid channel descriptor for '%s'\n",
65			 of_node_full_name(np));
66		return -EINVAL;
67	}
68
69	if (num_sh > 1) {
70		struct device_node *np_tx, *np_rx;
71
72		np_tx = of_parse_phandle(np, "shmem", 0);
73		np_rx = of_parse_phandle(np, "shmem", 1);
74		/* SCMI Tx and Rx shared mem areas have to be distinct */
75		if (!np_tx || !np_rx || np_tx == np_rx) {
76			dev_warn(cdev, "Invalid shmem descriptor for '%s'\n",
77				 of_node_full_name(np));
78			ret = -EINVAL;
79		}
80
81		of_node_put(np_tx);
82		of_node_put(np_rx);
83	}
84
85	return ret;
86}
87
88static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
89			      bool tx)
90{
91	const char *desc = tx ? "Tx" : "Rx";
92	struct device *cdev = cinfo->dev;
93	struct scmi_mailbox *smbox;
94	struct device_node *shmem;
95	int ret, idx = tx ? 0 : 1;
96	struct mbox_client *cl;
97	resource_size_t size;
98	struct resource res;
99
100	ret = mailbox_chan_validate(cdev);
101	if (ret)
102		return ret;
103
104	smbox = devm_kzalloc(dev, sizeof(*smbox), GFP_KERNEL);
105	if (!smbox)
106		return -ENOMEM;
107
108	shmem = of_parse_phandle(cdev->of_node, "shmem", idx);
109	ret = of_address_to_resource(shmem, 0, &res);
110	of_node_put(shmem);
111	if (ret) {
112		dev_err(cdev, "failed to get SCMI %s shared memory\n", desc);
113		return ret;
114	}
115
116	size = resource_size(&res);
117	smbox->shmem = devm_ioremap(dev, res.start, size);
118	if (!smbox->shmem) {
119		dev_err(dev, "failed to ioremap SCMI %s shared memory\n", desc);
120		return -EADDRNOTAVAIL;
121	}
122
123	cl = &smbox->cl;
124	cl->dev = cdev;
125	cl->tx_prepare = tx ? tx_prepare : NULL;
126	cl->rx_callback = rx_callback;
127	cl->tx_block = false;
128	cl->knows_txdone = tx;
129
130	smbox->chan = mbox_request_channel(cl, tx ? 0 : 1);
131	if (IS_ERR(smbox->chan)) {
132		ret = PTR_ERR(smbox->chan);
133		if (ret != -EPROBE_DEFER)
134			dev_err(cdev, "failed to request SCMI %s mailbox\n",
135				tx ? "Tx" : "Rx");
136		return ret;
137	}
138
139	cinfo->transport_info = smbox;
140	smbox->cinfo = cinfo;
141
142	return 0;
143}
144
145static int mailbox_chan_free(int id, void *p, void *data)
146{
147	struct scmi_chan_info *cinfo = p;
148	struct scmi_mailbox *smbox = cinfo->transport_info;
149
150	if (smbox && !IS_ERR(smbox->chan)) {
151		mbox_free_channel(smbox->chan);
152		cinfo->transport_info = NULL;
153		smbox->chan = NULL;
154		smbox->cinfo = NULL;
155	}
156
157	scmi_free_channel(cinfo, data, id);
158
159	return 0;
160}
161
162static int mailbox_send_message(struct scmi_chan_info *cinfo,
163				struct scmi_xfer *xfer)
164{
165	struct scmi_mailbox *smbox = cinfo->transport_info;
166	int ret;
167
168	ret = mbox_send_message(smbox->chan, xfer);
169
170	/* mbox_send_message returns non-negative value on success, so reset */
171	if (ret > 0)
172		ret = 0;
173
174	return ret;
175}
176
177static void mailbox_mark_txdone(struct scmi_chan_info *cinfo, int ret)
178{
179	struct scmi_mailbox *smbox = cinfo->transport_info;
180
181	/*
182	 * NOTE: we might prefer not to need the mailbox ticker to manage the
183	 * transfer queueing since the protocol layer queues things by itself.
184	 * Unfortunately, we have to kick the mailbox framework after we have
185	 * received our message.
186	 */
187	mbox_client_txdone(smbox->chan, ret);
188}
189
190static void mailbox_fetch_response(struct scmi_chan_info *cinfo,
191				   struct scmi_xfer *xfer)
192{
193	struct scmi_mailbox *smbox = cinfo->transport_info;
194
195	shmem_fetch_response(smbox->shmem, xfer);
196}
197
198static void mailbox_fetch_notification(struct scmi_chan_info *cinfo,
199				       size_t max_len, struct scmi_xfer *xfer)
200{
201	struct scmi_mailbox *smbox = cinfo->transport_info;
202
203	shmem_fetch_notification(smbox->shmem, max_len, xfer);
204}
205
206static void mailbox_clear_channel(struct scmi_chan_info *cinfo)
207{
208	struct scmi_mailbox *smbox = cinfo->transport_info;
209
210	shmem_clear_channel(smbox->shmem);
211}
212
213static bool
214mailbox_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
215{
216	struct scmi_mailbox *smbox = cinfo->transport_info;
217
218	return shmem_poll_done(smbox->shmem, xfer);
219}
220
221static const struct scmi_transport_ops scmi_mailbox_ops = {
222	.chan_available = mailbox_chan_available,
223	.chan_setup = mailbox_chan_setup,
224	.chan_free = mailbox_chan_free,
225	.send_message = mailbox_send_message,
226	.mark_txdone = mailbox_mark_txdone,
227	.fetch_response = mailbox_fetch_response,
228	.fetch_notification = mailbox_fetch_notification,
229	.clear_channel = mailbox_clear_channel,
230	.poll_done = mailbox_poll_done,
231};
232
233const struct scmi_desc scmi_mailbox_desc = {
234	.ops = &scmi_mailbox_ops,
235	.max_rx_timeout_ms = 30, /* We may increase this if required */
236	.max_msg = 20, /* Limited by MBOX_TX_QUEUE_LEN */
237	.max_msg_size = 128,
238};
239