1 // SPDX-License-Identifier: GPL-2.0
2 //
3 // Copyright (c) 2017-2019 Samuel Holland <samuel@sholland.org>
4
5 #include <linux/bitops.h>
6 #include <linux/clk.h>
7 #include <linux/device.h>
8 #include <linux/err.h>
9 #include <linux/interrupt.h>
10 #include <linux/io.h>
11 #include <linux/kernel.h>
12 #include <linux/mailbox_controller.h>
13 #include <linux/module.h>
14 #include <linux/of.h>
15 #include <linux/of_irq.h>
16 #include <linux/platform_device.h>
17 #include <linux/reset.h>
18 #include <linux/spinlock.h>
19
20 #define NUM_CHANS 8
21
22 #define CTRL_REG(n) (0x0000 + 0x4 * ((n) / 4))
23 #define CTRL_RX(n) BIT(0 + 8 * ((n) % 4))
24 #define CTRL_TX(n) BIT(4 + 8 * ((n) % 4))
25
26 #define REMOTE_IRQ_EN_REG 0x0040
27 #define REMOTE_IRQ_STAT_REG 0x0050
28 #define LOCAL_IRQ_EN_REG 0x0060
29 #define LOCAL_IRQ_STAT_REG 0x0070
30
31 #define RX_IRQ(n) BIT(0 + 2 * (n))
32 #define RX_IRQ_MASK 0x5555
33 #define TX_IRQ(n) BIT(1 + 2 * (n))
34 #define TX_IRQ_MASK 0xaaaa
35
36 #define FIFO_STAT_REG(n) (0x0100 + 0x4 * (n))
37 #define FIFO_STAT_MASK GENMASK(0, 0)
38
39 #define MSG_STAT_REG(n) (0x0140 + 0x4 * (n))
40 #define MSG_STAT_MASK GENMASK(2, 0)
41
42 #define MSG_DATA_REG(n) (0x0180 + 0x4 * (n))
43
44 #define mbox_dbg(mbox, ...) dev_dbg((mbox)->controller.dev, __VA_ARGS__)
45
46 struct sun6i_msgbox {
47 struct mbox_controller controller;
48 struct clk *clk;
49 spinlock_t lock;
50 void __iomem *regs;
51 };
52
53 static bool sun6i_msgbox_last_tx_done(struct mbox_chan *chan);
54 static bool sun6i_msgbox_peek_data(struct mbox_chan *chan);
55
channel_number(struct mbox_chan * chan)56 static inline int channel_number(struct mbox_chan *chan)
57 {
58 return chan - chan->mbox->chans;
59 }
60
to_sun6i_msgbox(struct mbox_chan * chan)61 static inline struct sun6i_msgbox *to_sun6i_msgbox(struct mbox_chan *chan)
62 {
63 return chan->con_priv;
64 }
65
sun6i_msgbox_irq(int irq,void * dev_id)66 static irqreturn_t sun6i_msgbox_irq(int irq, void *dev_id)
67 {
68 struct sun6i_msgbox *mbox = dev_id;
69 uint32_t status;
70 int n;
71
72 /* Only examine channels that are currently enabled. */
73 status = readl(mbox->regs + LOCAL_IRQ_EN_REG) &
74 readl(mbox->regs + LOCAL_IRQ_STAT_REG);
75
76 if (!(status & RX_IRQ_MASK))
77 return IRQ_NONE;
78
79 for (n = 0; n < NUM_CHANS; ++n) {
80 struct mbox_chan *chan = &mbox->controller.chans[n];
81
82 if (!(status & RX_IRQ(n)))
83 continue;
84
85 while (sun6i_msgbox_peek_data(chan)) {
86 uint32_t msg = readl(mbox->regs + MSG_DATA_REG(n));
87
88 mbox_dbg(mbox, "Channel %d received 0x%08x\n", n, msg);
89 mbox_chan_received_data(chan, &msg);
90 }
91
92 /* The IRQ can be cleared only once the FIFO is empty. */
93 writel(RX_IRQ(n), mbox->regs + LOCAL_IRQ_STAT_REG);
94 }
95
96 return IRQ_HANDLED;
97 }
98
sun6i_msgbox_send_data(struct mbox_chan * chan,void * data)99 static int sun6i_msgbox_send_data(struct mbox_chan *chan, void *data)
100 {
101 struct sun6i_msgbox *mbox = to_sun6i_msgbox(chan);
102 int n = channel_number(chan);
103 uint32_t msg = *(uint32_t *)data;
104
105 /* Using a channel backwards gets the hardware into a bad state. */
106 if (WARN_ON_ONCE(!(readl(mbox->regs + CTRL_REG(n)) & CTRL_TX(n))))
107 return 0;
108
109 writel(msg, mbox->regs + MSG_DATA_REG(n));
110 mbox_dbg(mbox, "Channel %d sent 0x%08x\n", n, msg);
111
112 return 0;
113 }
114
sun6i_msgbox_startup(struct mbox_chan * chan)115 static int sun6i_msgbox_startup(struct mbox_chan *chan)
116 {
117 struct sun6i_msgbox *mbox = to_sun6i_msgbox(chan);
118 int n = channel_number(chan);
119
120 /* The coprocessor is responsible for setting channel directions. */
121 if (readl(mbox->regs + CTRL_REG(n)) & CTRL_RX(n)) {
122 /* Flush the receive FIFO. */
123 while (sun6i_msgbox_peek_data(chan))
124 readl(mbox->regs + MSG_DATA_REG(n));
125 writel(RX_IRQ(n), mbox->regs + LOCAL_IRQ_STAT_REG);
126
127 /* Enable the receive IRQ. */
128 spin_lock(&mbox->lock);
129 writel(readl(mbox->regs + LOCAL_IRQ_EN_REG) | RX_IRQ(n),
130 mbox->regs + LOCAL_IRQ_EN_REG);
131 spin_unlock(&mbox->lock);
132 }
133
134 mbox_dbg(mbox, "Channel %d startup complete\n", n);
135
136 return 0;
137 }
138
sun6i_msgbox_shutdown(struct mbox_chan * chan)139 static void sun6i_msgbox_shutdown(struct mbox_chan *chan)
140 {
141 struct sun6i_msgbox *mbox = to_sun6i_msgbox(chan);
142 int n = channel_number(chan);
143
144 if (readl(mbox->regs + CTRL_REG(n)) & CTRL_RX(n)) {
145 /* Disable the receive IRQ. */
146 spin_lock(&mbox->lock);
147 writel(readl(mbox->regs + LOCAL_IRQ_EN_REG) & ~RX_IRQ(n),
148 mbox->regs + LOCAL_IRQ_EN_REG);
149 spin_unlock(&mbox->lock);
150
151 /* Attempt to flush the FIFO until the IRQ is cleared. */
152 do {
153 while (sun6i_msgbox_peek_data(chan))
154 readl(mbox->regs + MSG_DATA_REG(n));
155 writel(RX_IRQ(n), mbox->regs + LOCAL_IRQ_STAT_REG);
156 } while (readl(mbox->regs + LOCAL_IRQ_STAT_REG) & RX_IRQ(n));
157 }
158
159 mbox_dbg(mbox, "Channel %d shutdown complete\n", n);
160 }
161
sun6i_msgbox_last_tx_done(struct mbox_chan * chan)162 static bool sun6i_msgbox_last_tx_done(struct mbox_chan *chan)
163 {
164 struct sun6i_msgbox *mbox = to_sun6i_msgbox(chan);
165 int n = channel_number(chan);
166
167 /*
168 * The hardware allows snooping on the remote user's IRQ statuses.
169 * We consider a message to be acknowledged only once the receive IRQ
170 * for that channel is cleared. Since the receive IRQ for a channel
171 * cannot be cleared until the FIFO for that channel is empty, this
172 * ensures that the message has actually been read. It also gives the
173 * recipient an opportunity to perform minimal processing before
174 * acknowledging the message.
175 */
176 return !(readl(mbox->regs + REMOTE_IRQ_STAT_REG) & RX_IRQ(n));
177 }
178
sun6i_msgbox_peek_data(struct mbox_chan * chan)179 static bool sun6i_msgbox_peek_data(struct mbox_chan *chan)
180 {
181 struct sun6i_msgbox *mbox = to_sun6i_msgbox(chan);
182 int n = channel_number(chan);
183
184 return readl(mbox->regs + MSG_STAT_REG(n)) & MSG_STAT_MASK;
185 }
186
187 static const struct mbox_chan_ops sun6i_msgbox_chan_ops = {
188 .send_data = sun6i_msgbox_send_data,
189 .startup = sun6i_msgbox_startup,
190 .shutdown = sun6i_msgbox_shutdown,
191 .last_tx_done = sun6i_msgbox_last_tx_done,
192 .peek_data = sun6i_msgbox_peek_data,
193 };
194
sun6i_msgbox_probe(struct platform_device * pdev)195 static int sun6i_msgbox_probe(struct platform_device *pdev)
196 {
197 struct device *dev = &pdev->dev;
198 struct mbox_chan *chans;
199 struct reset_control *reset;
200 struct resource *res;
201 struct sun6i_msgbox *mbox;
202 int i, ret;
203
204 mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
205 if (!mbox)
206 return -ENOMEM;
207
208 chans = devm_kcalloc(dev, NUM_CHANS, sizeof(*chans), GFP_KERNEL);
209 if (!chans)
210 return -ENOMEM;
211
212 for (i = 0; i < NUM_CHANS; ++i)
213 chans[i].con_priv = mbox;
214
215 mbox->clk = devm_clk_get(dev, NULL);
216 if (IS_ERR(mbox->clk)) {
217 ret = PTR_ERR(mbox->clk);
218 dev_err(dev, "Failed to get clock: %d\n", ret);
219 return ret;
220 }
221
222 ret = clk_prepare_enable(mbox->clk);
223 if (ret) {
224 dev_err(dev, "Failed to enable clock: %d\n", ret);
225 return ret;
226 }
227
228 reset = devm_reset_control_get_exclusive(dev, NULL);
229 if (IS_ERR(reset)) {
230 ret = PTR_ERR(reset);
231 dev_err(dev, "Failed to get reset control: %d\n", ret);
232 goto err_disable_unprepare;
233 }
234
235 /*
236 * NOTE: We rely on platform firmware to preconfigure the channel
237 * directions, and we share this hardware block with other firmware
238 * that runs concurrently with Linux (e.g. a trusted monitor).
239 *
240 * Therefore, we do *not* assert the reset line if probing fails or
241 * when removing the device.
242 */
243 ret = reset_control_deassert(reset);
244 if (ret) {
245 dev_err(dev, "Failed to deassert reset: %d\n", ret);
246 goto err_disable_unprepare;
247 }
248
249 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
250 if (!res) {
251 ret = -ENODEV;
252 goto err_disable_unprepare;
253 }
254
255 mbox->regs = devm_ioremap_resource(&pdev->dev, res);
256 if (IS_ERR(mbox->regs)) {
257 ret = PTR_ERR(mbox->regs);
258 dev_err(dev, "Failed to map MMIO resource: %d\n", ret);
259 goto err_disable_unprepare;
260 }
261
262 /* Disable all IRQs for this end of the msgbox. */
263 writel(0, mbox->regs + LOCAL_IRQ_EN_REG);
264
265 ret = devm_request_irq(dev, irq_of_parse_and_map(dev->of_node, 0),
266 sun6i_msgbox_irq, 0, dev_name(dev), mbox);
267 if (ret) {
268 dev_err(dev, "Failed to register IRQ handler: %d\n", ret);
269 goto err_disable_unprepare;
270 }
271
272 mbox->controller.dev = dev;
273 mbox->controller.ops = &sun6i_msgbox_chan_ops;
274 mbox->controller.chans = chans;
275 mbox->controller.num_chans = NUM_CHANS;
276 mbox->controller.txdone_irq = false;
277 mbox->controller.txdone_poll = true;
278 mbox->controller.txpoll_period = 5;
279
280 spin_lock_init(&mbox->lock);
281 platform_set_drvdata(pdev, mbox);
282
283 ret = mbox_controller_register(&mbox->controller);
284 if (ret) {
285 dev_err(dev, "Failed to register controller: %d\n", ret);
286 goto err_disable_unprepare;
287 }
288
289 return 0;
290
291 err_disable_unprepare:
292 clk_disable_unprepare(mbox->clk);
293
294 return ret;
295 }
296
sun6i_msgbox_remove(struct platform_device * pdev)297 static int sun6i_msgbox_remove(struct platform_device *pdev)
298 {
299 struct sun6i_msgbox *mbox = platform_get_drvdata(pdev);
300
301 mbox_controller_unregister(&mbox->controller);
302 /* See the comment in sun6i_msgbox_probe about the reset line. */
303 clk_disable_unprepare(mbox->clk);
304
305 return 0;
306 }
307
308 static const struct of_device_id sun6i_msgbox_of_match[] = {
309 { .compatible = "allwinner,sun6i-a31-msgbox", },
310 {},
311 };
312 MODULE_DEVICE_TABLE(of, sun6i_msgbox_of_match);
313
314 static struct platform_driver sun6i_msgbox_driver = {
315 .driver = {
316 .name = "sun6i-msgbox",
317 .of_match_table = sun6i_msgbox_of_match,
318 },
319 .probe = sun6i_msgbox_probe,
320 .remove = sun6i_msgbox_remove,
321 };
322 module_platform_driver(sun6i_msgbox_driver);
323
324 MODULE_AUTHOR("Samuel Holland <samuel@sholland.org>");
325 MODULE_DESCRIPTION("Allwinner sun6i/sun8i/sun9i/sun50i Message Box");
326 MODULE_LICENSE("GPL v2");
327