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
84struct 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
94static 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
112static u32 p2wi_functionality(struct i2c_adapter *adap)
113{
114	return I2C_FUNC_SMBUS_BYTE_DATA;
115}
116
117static 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
172static const struct i2c_algorithm p2wi_algo = {
173	.smbus_xfer = p2wi_smbus_xfer,
174	.functionality = p2wi_functionality,
175};
176
177static const struct of_device_id p2wi_of_match_table[] = {
178	{ .compatible = "allwinner,sun6i-a31-p2wi" },
179	{}
180};
181MODULE_DEVICE_TABLE(of, p2wi_of_match_table);
182
183static 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
306err_reset_assert:
307	reset_control_assert(p2wi->rstc);
308
309	return ret;
310}
311
312static 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
320static 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};
328module_platform_driver(p2wi_driver);
329
330MODULE_AUTHOR("Boris BREZILLON <boris.brezillon@free-electrons.com>");
331MODULE_DESCRIPTION("Allwinner P2WI driver");
332MODULE_LICENSE("GPL v2");
333