1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright 2005-2008 Freescale Semiconductor, Inc. All Rights Reserved.
4 * Copyright 2008 Luotao Fu, kernel@pengutronix.de
5 */
6
7 #include <linux/clk.h>
8 #include <linux/delay.h>
9 #include <linux/io.h>
10 #include <linux/ktime.h>
11 #include <linux/module.h>
12 #include <linux/mod_devicetable.h>
13 #include <linux/platform_device.h>
14
15 #include <linux/w1.h>
16
17 /*
18 * MXC W1 Register offsets
19 */
20 #define MXC_W1_CONTROL 0x00
21 # define MXC_W1_CONTROL_RDST BIT(3)
22 # define MXC_W1_CONTROL_WR(x) BIT(5 - (x))
23 # define MXC_W1_CONTROL_PST BIT(6)
24 # define MXC_W1_CONTROL_RPP BIT(7)
25 #define MXC_W1_TIME_DIVIDER 0x02
26 #define MXC_W1_RESET 0x04
27 # define MXC_W1_RESET_RST BIT(0)
28
29 struct mxc_w1_device {
30 void __iomem *regs;
31 struct clk *clk;
32 struct w1_bus_master bus_master;
33 };
34
35 /*
36 * this is the low level routine to
37 * reset the device on the One Wire interface
38 * on the hardware
39 */
mxc_w1_ds2_reset_bus(void * data)40 static u8 mxc_w1_ds2_reset_bus(void *data)
41 {
42 struct mxc_w1_device *dev = data;
43 ktime_t timeout;
44
45 writeb(MXC_W1_CONTROL_RPP, dev->regs + MXC_W1_CONTROL);
46
47 /* Wait for reset sequence 511+512us, use 1500us for sure */
48 timeout = ktime_add_us(ktime_get(), 1500);
49
50 udelay(511 + 512);
51
52 do {
53 u8 ctrl = readb(dev->regs + MXC_W1_CONTROL);
54
55 /* PST bit is valid after the RPP bit is self-cleared */
56 if (!(ctrl & MXC_W1_CONTROL_RPP))
57 return !(ctrl & MXC_W1_CONTROL_PST);
58 } while (ktime_before(ktime_get(), timeout));
59
60 return 1;
61 }
62
63 /*
64 * this is the low level routine to read/write a bit on the One Wire
65 * interface on the hardware. It does write 0 if parameter bit is set
66 * to 0, otherwise a write 1/read.
67 */
mxc_w1_ds2_touch_bit(void * data,u8 bit)68 static u8 mxc_w1_ds2_touch_bit(void *data, u8 bit)
69 {
70 struct mxc_w1_device *dev = data;
71 ktime_t timeout;
72
73 writeb(MXC_W1_CONTROL_WR(bit), dev->regs + MXC_W1_CONTROL);
74
75 /* Wait for read/write bit (60us, Max 120us), use 200us for sure */
76 timeout = ktime_add_us(ktime_get(), 200);
77
78 udelay(60);
79
80 do {
81 u8 ctrl = readb(dev->regs + MXC_W1_CONTROL);
82
83 /* RDST bit is valid after the WR1/RD bit is self-cleared */
84 if (!(ctrl & MXC_W1_CONTROL_WR(bit)))
85 return !!(ctrl & MXC_W1_CONTROL_RDST);
86 } while (ktime_before(ktime_get(), timeout));
87
88 return 0;
89 }
90
mxc_w1_probe(struct platform_device * pdev)91 static int mxc_w1_probe(struct platform_device *pdev)
92 {
93 struct mxc_w1_device *mdev;
94 unsigned long clkrate;
95 unsigned int clkdiv;
96 int err;
97
98 mdev = devm_kzalloc(&pdev->dev, sizeof(struct mxc_w1_device),
99 GFP_KERNEL);
100 if (!mdev)
101 return -ENOMEM;
102
103 mdev->clk = devm_clk_get(&pdev->dev, NULL);
104 if (IS_ERR(mdev->clk))
105 return PTR_ERR(mdev->clk);
106
107 err = clk_prepare_enable(mdev->clk);
108 if (err)
109 return err;
110
111 clkrate = clk_get_rate(mdev->clk);
112 if (clkrate < 10000000)
113 dev_warn(&pdev->dev,
114 "Low clock frequency causes improper function\n");
115
116 clkdiv = DIV_ROUND_CLOSEST(clkrate, 1000000);
117 clkrate /= clkdiv;
118 if ((clkrate < 980000) || (clkrate > 1020000))
119 dev_warn(&pdev->dev,
120 "Incorrect time base frequency %lu Hz\n", clkrate);
121
122 mdev->regs = devm_platform_ioremap_resource(pdev, 0);
123 if (IS_ERR(mdev->regs)) {
124 err = PTR_ERR(mdev->regs);
125 goto out_disable_clk;
126 }
127
128 /* Software reset 1-Wire module */
129 writeb(MXC_W1_RESET_RST, mdev->regs + MXC_W1_RESET);
130 writeb(0, mdev->regs + MXC_W1_RESET);
131
132 writeb(clkdiv - 1, mdev->regs + MXC_W1_TIME_DIVIDER);
133
134 mdev->bus_master.data = mdev;
135 mdev->bus_master.reset_bus = mxc_w1_ds2_reset_bus;
136 mdev->bus_master.touch_bit = mxc_w1_ds2_touch_bit;
137
138 platform_set_drvdata(pdev, mdev);
139
140 err = w1_add_master_device(&mdev->bus_master);
141 if (err)
142 goto out_disable_clk;
143
144 return 0;
145
146 out_disable_clk:
147 clk_disable_unprepare(mdev->clk);
148 return err;
149 }
150
151 /*
152 * disassociate the w1 device from the driver
153 */
mxc_w1_remove(struct platform_device * pdev)154 static int mxc_w1_remove(struct platform_device *pdev)
155 {
156 struct mxc_w1_device *mdev = platform_get_drvdata(pdev);
157
158 w1_remove_master_device(&mdev->bus_master);
159
160 clk_disable_unprepare(mdev->clk);
161
162 return 0;
163 }
164
165 static const struct of_device_id mxc_w1_dt_ids[] = {
166 { .compatible = "fsl,imx21-owire" },
167 { /* sentinel */ }
168 };
169 MODULE_DEVICE_TABLE(of, mxc_w1_dt_ids);
170
171 static struct platform_driver mxc_w1_driver = {
172 .driver = {
173 .name = "mxc_w1",
174 .of_match_table = mxc_w1_dt_ids,
175 },
176 .probe = mxc_w1_probe,
177 .remove = mxc_w1_remove,
178 };
179 module_platform_driver(mxc_w1_driver);
180
181 MODULE_LICENSE("GPL");
182 MODULE_AUTHOR("Freescale Semiconductors Inc");
183 MODULE_DESCRIPTION("Driver for One-Wire on MXC");
184