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  */
26 struct 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 
35 static 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 
42 static 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), NULL);
47 }
48 
49 static 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 
55 static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
56 			      bool tx)
57 {
58 	const char *desc = tx ? "Tx" : "Rx";
59 	struct device *cdev = cinfo->dev;
60 	struct scmi_mailbox *smbox;
61 	struct device_node *shmem;
62 	int ret, idx = tx ? 0 : 1;
63 	struct mbox_client *cl;
64 	resource_size_t size;
65 	struct resource res;
66 
67 	smbox = devm_kzalloc(dev, sizeof(*smbox), GFP_KERNEL);
68 	if (!smbox)
69 		return -ENOMEM;
70 
71 	shmem = of_parse_phandle(cdev->of_node, "shmem", idx);
72 	if (!of_device_is_compatible(shmem, "arm,scmi-shmem"))
73 		return -ENXIO;
74 
75 	ret = of_address_to_resource(shmem, 0, &res);
76 	of_node_put(shmem);
77 	if (ret) {
78 		dev_err(cdev, "failed to get SCMI %s shared memory\n", desc);
79 		return ret;
80 	}
81 
82 	size = resource_size(&res);
83 	smbox->shmem = devm_ioremap(dev, res.start, size);
84 	if (!smbox->shmem) {
85 		dev_err(dev, "failed to ioremap SCMI %s shared memory\n", desc);
86 		return -EADDRNOTAVAIL;
87 	}
88 
89 	cl = &smbox->cl;
90 	cl->dev = cdev;
91 	cl->tx_prepare = tx ? tx_prepare : NULL;
92 	cl->rx_callback = rx_callback;
93 	cl->tx_block = false;
94 	cl->knows_txdone = tx;
95 
96 	smbox->chan = mbox_request_channel(cl, tx ? 0 : 1);
97 	if (IS_ERR(smbox->chan)) {
98 		ret = PTR_ERR(smbox->chan);
99 		if (ret != -EPROBE_DEFER)
100 			dev_err(cdev, "failed to request SCMI %s mailbox\n",
101 				tx ? "Tx" : "Rx");
102 		return ret;
103 	}
104 
105 	cinfo->transport_info = smbox;
106 	smbox->cinfo = cinfo;
107 
108 	return 0;
109 }
110 
111 static int mailbox_chan_free(int id, void *p, void *data)
112 {
113 	struct scmi_chan_info *cinfo = p;
114 	struct scmi_mailbox *smbox = cinfo->transport_info;
115 
116 	if (smbox && !IS_ERR(smbox->chan)) {
117 		mbox_free_channel(smbox->chan);
118 		cinfo->transport_info = NULL;
119 		smbox->chan = NULL;
120 		smbox->cinfo = NULL;
121 	}
122 
123 	scmi_free_channel(cinfo, data, id);
124 
125 	return 0;
126 }
127 
128 static int mailbox_send_message(struct scmi_chan_info *cinfo,
129 				struct scmi_xfer *xfer)
130 {
131 	struct scmi_mailbox *smbox = cinfo->transport_info;
132 	int ret;
133 
134 	ret = mbox_send_message(smbox->chan, xfer);
135 
136 	/* mbox_send_message returns non-negative value on success, so reset */
137 	if (ret > 0)
138 		ret = 0;
139 
140 	return ret;
141 }
142 
143 static void mailbox_mark_txdone(struct scmi_chan_info *cinfo, int ret,
144 				struct scmi_xfer *__unused)
145 {
146 	struct scmi_mailbox *smbox = cinfo->transport_info;
147 
148 	/*
149 	 * NOTE: we might prefer not to need the mailbox ticker to manage the
150 	 * transfer queueing since the protocol layer queues things by itself.
151 	 * Unfortunately, we have to kick the mailbox framework after we have
152 	 * received our message.
153 	 */
154 	mbox_client_txdone(smbox->chan, ret);
155 }
156 
157 static void mailbox_fetch_response(struct scmi_chan_info *cinfo,
158 				   struct scmi_xfer *xfer)
159 {
160 	struct scmi_mailbox *smbox = cinfo->transport_info;
161 
162 	shmem_fetch_response(smbox->shmem, xfer);
163 }
164 
165 static void mailbox_fetch_notification(struct scmi_chan_info *cinfo,
166 				       size_t max_len, struct scmi_xfer *xfer)
167 {
168 	struct scmi_mailbox *smbox = cinfo->transport_info;
169 
170 	shmem_fetch_notification(smbox->shmem, max_len, xfer);
171 }
172 
173 static void mailbox_clear_channel(struct scmi_chan_info *cinfo)
174 {
175 	struct scmi_mailbox *smbox = cinfo->transport_info;
176 
177 	shmem_clear_channel(smbox->shmem);
178 }
179 
180 static bool
181 mailbox_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
182 {
183 	struct scmi_mailbox *smbox = cinfo->transport_info;
184 
185 	return shmem_poll_done(smbox->shmem, xfer);
186 }
187 
188 static const struct scmi_transport_ops scmi_mailbox_ops = {
189 	.chan_available = mailbox_chan_available,
190 	.chan_setup = mailbox_chan_setup,
191 	.chan_free = mailbox_chan_free,
192 	.send_message = mailbox_send_message,
193 	.mark_txdone = mailbox_mark_txdone,
194 	.fetch_response = mailbox_fetch_response,
195 	.fetch_notification = mailbox_fetch_notification,
196 	.clear_channel = mailbox_clear_channel,
197 	.poll_done = mailbox_poll_done,
198 };
199 
200 const struct scmi_desc scmi_mailbox_desc = {
201 	.ops = &scmi_mailbox_ops,
202 	.max_rx_timeout_ms = 30, /* We may increase this if required */
203 	.max_msg = 20, /* Limited by MBOX_TX_QUEUE_LEN */
204 	.max_msg_size = 128,
205 };
206