1 /*
2  * P2WI (Push-Pull Two Wire Interface) bus driver.
3  *
4  * Author: Boris BREZILLON <boris.brezillon@free-electrons.com>
5  *
6  * This file is licensed under the terms of the GNU General Public License
7  * version 2.  This program is licensed "as is" without any warranty of any
8  * kind, whether express or implied.
9  *
10  * The P2WI controller looks like an SMBus controller which only supports byte
11  * data transfers. But, it differs from standard SMBus protocol on several
12  * aspects:
13  * - it supports only one slave device, and thus drop the address field
14  * - it adds a parity bit every 8bits of data
15  * - only one read access is required to read a byte (instead of a write
16  *   followed by a read access in standard SMBus protocol)
17  * - there's no Ack bit after each byte transfer
18  *
19  * This means this bus cannot be used to interface with standard SMBus
20  * devices (the only known device to support this interface is the AXP221
21  * PMIC).
22  *
23  */
24 #include <linux/clk.h>
25 #include <linux/i2c.h>
26 #include <linux/io.h>
27 #include <linux/interrupt.h>
28 #include <linux/module.h>
29 #include <linux/of.h>
30 #include <linux/platform_device.h>
31 #include <linux/reset.h>
32 
33 
34 /* P2WI registers */
35 #define P2WI_CTRL		0x0
36 #define P2WI_CCR		0x4
37 #define P2WI_INTE		0x8
38 #define P2WI_INTS		0xc
39 #define P2WI_DADDR0		0x10
40 #define P2WI_DADDR1		0x14
41 #define P2WI_DLEN		0x18
42 #define P2WI_DATA0		0x1c
43 #define P2WI_DATA1		0x20
44 #define P2WI_LCR		0x24
45 #define P2WI_PMCR		0x28
46 
47 /* CTRL fields */
48 #define P2WI_CTRL_START_TRANS		BIT(7)
49 #define P2WI_CTRL_ABORT_TRANS		BIT(6)
50 #define P2WI_CTRL_GLOBAL_INT_ENB	BIT(1)
51 #define P2WI_CTRL_SOFT_RST		BIT(0)
52 
53 /* CLK CTRL fields */
54 #define P2WI_CCR_SDA_OUT_DELAY(v)	(((v) & 0x7) << 8)
55 #define P2WI_CCR_MAX_CLK_DIV		0xff
56 #define P2WI_CCR_CLK_DIV(v)		((v) & P2WI_CCR_MAX_CLK_DIV)
57 
58 /* STATUS fields */
59 #define P2WI_INTS_TRANS_ERR_ID(v)	(((v) >> 8) & 0xff)
60 #define P2WI_INTS_LOAD_BSY		BIT(2)
61 #define P2WI_INTS_TRANS_ERR		BIT(1)
62 #define P2WI_INTS_TRANS_OVER		BIT(0)
63 
64 /* DATA LENGTH fields*/
65 #define P2WI_DLEN_READ			BIT(4)
66 #define P2WI_DLEN_DATA_LENGTH(v)	((v - 1) & 0x7)
67 
68 /* LINE CTRL fields*/
69 #define P2WI_LCR_SCL_STATE		BIT(5)
70 #define P2WI_LCR_SDA_STATE		BIT(4)
71 #define P2WI_LCR_SCL_CTL		BIT(3)
72 #define P2WI_LCR_SCL_CTL_EN		BIT(2)
73 #define P2WI_LCR_SDA_CTL		BIT(1)
74 #define P2WI_LCR_SDA_CTL_EN		BIT(0)
75 
76 /* PMU MODE CTRL fields */
77 #define P2WI_PMCR_PMU_INIT_SEND		BIT(31)
78 #define P2WI_PMCR_PMU_INIT_DATA(v)	(((v) & 0xff) << 16)
79 #define P2WI_PMCR_PMU_MODE_REG(v)	(((v) & 0xff) << 8)
80 #define P2WI_PMCR_PMU_DEV_ADDR(v)	((v) & 0xff)
81 
82 #define P2WI_MAX_FREQ			6000000
83 
84 struct p2wi {
85 	struct i2c_adapter adapter;
86 	struct completion complete;
87 	unsigned int status;
88 	void __iomem *regs;
89 	struct clk *clk;
90 	struct reset_control *rstc;
91 	int slave_addr;
92 };
93 
94 static irqreturn_t p2wi_interrupt(int irq, void *dev_id)
95 {
96 	struct p2wi *p2wi = dev_id;
97 	unsigned long status;
98 
99 	status = readl(p2wi->regs + P2WI_INTS);
100 	p2wi->status = status;
101 
102 	/* Clear interrupts */
103 	status &= (P2WI_INTS_LOAD_BSY | P2WI_INTS_TRANS_ERR |
104 		   P2WI_INTS_TRANS_OVER);
105 	writel(status, p2wi->regs + P2WI_INTS);
106 
107 	complete(&p2wi->complete);
108 
109 	return IRQ_HANDLED;
110 }
111 
112 static u32 p2wi_functionality(struct i2c_adapter *adap)
113 {
114 	return I2C_FUNC_SMBUS_BYTE_DATA;
115 }
116 
117 static int p2wi_smbus_xfer(struct i2c_adapter *adap, u16 addr,
118 			   unsigned short flags, char read_write,
119 			   u8 command, int size, union i2c_smbus_data *data)
120 {
121 	struct p2wi *p2wi = i2c_get_adapdata(adap);
122 	unsigned long dlen = P2WI_DLEN_DATA_LENGTH(1);
123 
124 	if (p2wi->slave_addr >= 0 && addr != p2wi->slave_addr) {
125 		dev_err(&adap->dev, "invalid P2WI address\n");
126 		return -EINVAL;
127 	}
128 
129 	if (!data)
130 		return -EINVAL;
131 
132 	writel(command, p2wi->regs + P2WI_DADDR0);
133 
134 	if (read_write == I2C_SMBUS_READ)
135 		dlen |= P2WI_DLEN_READ;
136 	else
137 		writel(data->byte, p2wi->regs + P2WI_DATA0);
138 
139 	writel(dlen, p2wi->regs + P2WI_DLEN);
140 
141 	if (readl(p2wi->regs + P2WI_CTRL) & P2WI_CTRL_START_TRANS) {
142 		dev_err(&adap->dev, "P2WI bus busy\n");
143 		return -EBUSY;
144 	}
145 
146 	reinit_completion(&p2wi->complete);
147 
148 	writel(P2WI_INTS_LOAD_BSY | P2WI_INTS_TRANS_ERR | P2WI_INTS_TRANS_OVER,
149 	       p2wi->regs + P2WI_INTE);
150 
151 	writel(P2WI_CTRL_START_TRANS | P2WI_CTRL_GLOBAL_INT_ENB,
152 	       p2wi->regs + P2WI_CTRL);
153 
154 	wait_for_completion(&p2wi->complete);
155 
156 	if (p2wi->status & P2WI_INTS_LOAD_BSY) {
157 		dev_err(&adap->dev, "P2WI bus busy\n");
158 		return -EBUSY;
159 	}
160 
161 	if (p2wi->status & P2WI_INTS_TRANS_ERR) {
162 		dev_err(&adap->dev, "P2WI bus xfer error\n");
163 		return -ENXIO;
164 	}
165 
166 	if (read_write == I2C_SMBUS_READ)
167 		data->byte = readl(p2wi->regs + P2WI_DATA0);
168 
169 	return 0;
170 }
171 
172 static const struct i2c_algorithm p2wi_algo = {
173 	.smbus_xfer = p2wi_smbus_xfer,
174 	.functionality = p2wi_functionality,
175 };
176 
177 static const struct of_device_id p2wi_of_match_table[] = {
178 	{ .compatible = "allwinner,sun6i-a31-p2wi" },
179 	{}
180 };
181 MODULE_DEVICE_TABLE(of, p2wi_of_match_table);
182 
183 static int p2wi_probe(struct platform_device *pdev)
184 {
185 	struct device *dev = &pdev->dev;
186 	struct device_node *np = dev->of_node;
187 	struct device_node *childnp;
188 	unsigned long parent_clk_freq;
189 	u32 clk_freq = I2C_MAX_STANDARD_MODE_FREQ;
190 	struct p2wi *p2wi;
191 	u32 slave_addr;
192 	int clk_div;
193 	int irq;
194 	int ret;
195 
196 	of_property_read_u32(np, "clock-frequency", &clk_freq);
197 	if (clk_freq > P2WI_MAX_FREQ) {
198 		dev_err(dev,
199 			"required clock-frequency (%u Hz) is too high (max = 6MHz)",
200 			clk_freq);
201 		return -EINVAL;
202 	}
203 
204 	if (clk_freq == 0) {
205 		dev_err(dev, "clock-frequency is set to 0 in DT\n");
206 		return -EINVAL;
207 	}
208 
209 	if (of_get_child_count(np) > 1) {
210 		dev_err(dev, "P2WI only supports one slave device\n");
211 		return -EINVAL;
212 	}
213 
214 	p2wi = devm_kzalloc(dev, sizeof(struct p2wi), GFP_KERNEL);
215 	if (!p2wi)
216 		return -ENOMEM;
217 
218 	p2wi->slave_addr = -1;
219 
220 	/*
221 	 * Authorize a p2wi node without any children to be able to use an
222 	 * i2c-dev from userpace.
223 	 * In this case the slave_addr is set to -1 and won't be checked when
224 	 * launching a P2WI transfer.
225 	 */
226 	childnp = of_get_next_available_child(np, NULL);
227 	if (childnp) {
228 		ret = of_property_read_u32(childnp, "reg", &slave_addr);
229 		if (ret) {
230 			dev_err(dev, "invalid slave address on node %pOF\n",
231 				childnp);
232 			return -EINVAL;
233 		}
234 
235 		p2wi->slave_addr = slave_addr;
236 	}
237 
238 	p2wi->regs = devm_platform_ioremap_resource(pdev, 0);
239 	if (IS_ERR(p2wi->regs))
240 		return PTR_ERR(p2wi->regs);
241 
242 	strscpy(p2wi->adapter.name, pdev->name, sizeof(p2wi->adapter.name));
243 	irq = platform_get_irq(pdev, 0);
244 	if (irq < 0)
245 		return irq;
246 
247 	p2wi->clk = devm_clk_get_enabled(dev, NULL);
248 	if (IS_ERR(p2wi->clk)) {
249 		ret = PTR_ERR(p2wi->clk);
250 		dev_err(dev, "failed to enable clk: %d\n", ret);
251 		return ret;
252 	}
253 
254 	parent_clk_freq = clk_get_rate(p2wi->clk);
255 
256 	p2wi->rstc = devm_reset_control_get_exclusive(dev, NULL);
257 	if (IS_ERR(p2wi->rstc)) {
258 		dev_err(dev, "failed to retrieve reset controller: %pe\n",
259 			p2wi->rstc);
260 		return PTR_ERR(p2wi->rstc);
261 	}
262 
263 	ret = reset_control_deassert(p2wi->rstc);
264 	if (ret) {
265 		dev_err(dev, "failed to deassert reset line: %d\n", ret);
266 		return ret;
267 	}
268 
269 	init_completion(&p2wi->complete);
270 	p2wi->adapter.dev.parent = dev;
271 	p2wi->adapter.algo = &p2wi_algo;
272 	p2wi->adapter.owner = THIS_MODULE;
273 	p2wi->adapter.dev.of_node = pdev->dev.of_node;
274 	platform_set_drvdata(pdev, p2wi);
275 	i2c_set_adapdata(&p2wi->adapter, p2wi);
276 
277 	ret = devm_request_irq(dev, irq, p2wi_interrupt, 0, pdev->name, p2wi);
278 	if (ret) {
279 		dev_err(dev, "can't register interrupt handler irq%d: %d\n",
280 			irq, ret);
281 		goto err_reset_assert;
282 	}
283 
284 	writel(P2WI_CTRL_SOFT_RST, p2wi->regs + P2WI_CTRL);
285 
286 	clk_div = parent_clk_freq / clk_freq;
287 	if (!clk_div) {
288 		dev_warn(dev,
289 			 "clock-frequency is too high, setting it to %lu Hz\n",
290 			 parent_clk_freq);
291 		clk_div = 1;
292 	} else if (clk_div > P2WI_CCR_MAX_CLK_DIV) {
293 		dev_warn(dev,
294 			 "clock-frequency is too low, setting it to %lu Hz\n",
295 			 parent_clk_freq / P2WI_CCR_MAX_CLK_DIV);
296 		clk_div = P2WI_CCR_MAX_CLK_DIV;
297 	}
298 
299 	writel(P2WI_CCR_SDA_OUT_DELAY(1) | P2WI_CCR_CLK_DIV(clk_div),
300 	       p2wi->regs + P2WI_CCR);
301 
302 	ret = i2c_add_adapter(&p2wi->adapter);
303 	if (!ret)
304 		return 0;
305 
306 err_reset_assert:
307 	reset_control_assert(p2wi->rstc);
308 
309 	return ret;
310 }
311 
312 static void p2wi_remove(struct platform_device *dev)
313 {
314 	struct p2wi *p2wi = platform_get_drvdata(dev);
315 
316 	reset_control_assert(p2wi->rstc);
317 	i2c_del_adapter(&p2wi->adapter);
318 }
319 
320 static struct platform_driver p2wi_driver = {
321 	.probe	= p2wi_probe,
322 	.remove_new = p2wi_remove,
323 	.driver	= {
324 		.name = "i2c-sunxi-p2wi",
325 		.of_match_table = p2wi_of_match_table,
326 	},
327 };
328 module_platform_driver(p2wi_driver);
329 
330 MODULE_AUTHOR("Boris BREZILLON <boris.brezillon@free-electrons.com>");
331 MODULE_DESCRIPTION("Allwinner P2WI driver");
332 MODULE_LICENSE("GPL v2");
333