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 sun6i_msgbox *mbox;
201 	int i, ret;
202 
203 	mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
204 	if (!mbox)
205 		return -ENOMEM;
206 
207 	chans = devm_kcalloc(dev, NUM_CHANS, sizeof(*chans), GFP_KERNEL);
208 	if (!chans)
209 		return -ENOMEM;
210 
211 	for (i = 0; i < NUM_CHANS; ++i)
212 		chans[i].con_priv = mbox;
213 
214 	mbox->clk = devm_clk_get(dev, NULL);
215 	if (IS_ERR(mbox->clk)) {
216 		ret = PTR_ERR(mbox->clk);
217 		dev_err(dev, "Failed to get clock: %d\n", ret);
218 		return ret;
219 	}
220 
221 	ret = clk_prepare_enable(mbox->clk);
222 	if (ret) {
223 		dev_err(dev, "Failed to enable clock: %d\n", ret);
224 		return ret;
225 	}
226 
227 	reset = devm_reset_control_get_exclusive(dev, NULL);
228 	if (IS_ERR(reset)) {
229 		ret = PTR_ERR(reset);
230 		dev_err(dev, "Failed to get reset control: %d\n", ret);
231 		goto err_disable_unprepare;
232 	}
233 
234 	/*
235 	 * NOTE: We rely on platform firmware to preconfigure the channel
236 	 * directions, and we share this hardware block with other firmware
237 	 * that runs concurrently with Linux (e.g. a trusted monitor).
238 	 *
239 	 * Therefore, we do *not* assert the reset line if probing fails or
240 	 * when removing the device.
241 	 */
242 	ret = reset_control_deassert(reset);
243 	if (ret) {
244 		dev_err(dev, "Failed to deassert reset: %d\n", ret);
245 		goto err_disable_unprepare;
246 	}
247 
248 	mbox->regs = devm_platform_ioremap_resource(pdev, 0);
249 	if (IS_ERR(mbox->regs)) {
250 		ret = PTR_ERR(mbox->regs);
251 		dev_err(dev, "Failed to map MMIO resource: %d\n", ret);
252 		goto err_disable_unprepare;
253 	}
254 
255 	/* Disable all IRQs for this end of the msgbox. */
256 	writel(0, mbox->regs + LOCAL_IRQ_EN_REG);
257 
258 	ret = devm_request_irq(dev, irq_of_parse_and_map(dev->of_node, 0),
259 			       sun6i_msgbox_irq, 0, dev_name(dev), mbox);
260 	if (ret) {
261 		dev_err(dev, "Failed to register IRQ handler: %d\n", ret);
262 		goto err_disable_unprepare;
263 	}
264 
265 	mbox->controller.dev           = dev;
266 	mbox->controller.ops           = &sun6i_msgbox_chan_ops;
267 	mbox->controller.chans         = chans;
268 	mbox->controller.num_chans     = NUM_CHANS;
269 	mbox->controller.txdone_irq    = false;
270 	mbox->controller.txdone_poll   = true;
271 	mbox->controller.txpoll_period = 5;
272 
273 	spin_lock_init(&mbox->lock);
274 	platform_set_drvdata(pdev, mbox);
275 
276 	ret = mbox_controller_register(&mbox->controller);
277 	if (ret) {
278 		dev_err(dev, "Failed to register controller: %d\n", ret);
279 		goto err_disable_unprepare;
280 	}
281 
282 	return 0;
283 
284 err_disable_unprepare:
285 	clk_disable_unprepare(mbox->clk);
286 
287 	return ret;
288 }
289 
sun6i_msgbox_remove(struct platform_device * pdev)290 static int sun6i_msgbox_remove(struct platform_device *pdev)
291 {
292 	struct sun6i_msgbox *mbox = platform_get_drvdata(pdev);
293 
294 	mbox_controller_unregister(&mbox->controller);
295 	/* See the comment in sun6i_msgbox_probe about the reset line. */
296 	clk_disable_unprepare(mbox->clk);
297 
298 	return 0;
299 }
300 
301 static const struct of_device_id sun6i_msgbox_of_match[] = {
302 	{ .compatible = "allwinner,sun6i-a31-msgbox", },
303 	{},
304 };
305 MODULE_DEVICE_TABLE(of, sun6i_msgbox_of_match);
306 
307 static struct platform_driver sun6i_msgbox_driver = {
308 	.driver = {
309 		.name = "sun6i-msgbox",
310 		.of_match_table = sun6i_msgbox_of_match,
311 	},
312 	.probe  = sun6i_msgbox_probe,
313 	.remove = sun6i_msgbox_remove,
314 };
315 module_platform_driver(sun6i_msgbox_driver);
316 
317 MODULE_AUTHOR("Samuel Holland <samuel@sholland.org>");
318 MODULE_DESCRIPTION("Allwinner sun6i/sun8i/sun9i/sun50i Message Box");
319 MODULE_LICENSE("GPL v2");
320