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Linux/drivers/w1/masters/mxc_w1.c

  1 /*
  2  * Copyright 2005-2008 Freescale Semiconductor, Inc. All Rights Reserved.
  3  * Copyright 2008 Luotao Fu, kernel@pengutronix.de
  4  *
  5  * This program is free software; you can redistribute it and/or
  6  * modify it under the terms of the GNU General Public License
  7  * as published by the Free Software Foundation; either version 2
  8  * of the License, or (at your option) any later version.
  9  * This program is distributed in the hope that it will be useful,
 10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12  * GNU General Public License for more details.
 13  */
 14 
 15 #include <linux/clk.h>
 16 #include <linux/delay.h>
 17 #include <linux/io.h>
 18 #include <linux/module.h>
 19 #include <linux/platform_device.h>
 20 
 21 #include "../w1.h"
 22 #include "../w1_int.h"
 23 
 24 /* According to the mx27 Datasheet the reset procedure should take up to about
 25  * 1350us. We set the timeout to 500*100us = 50ms for sure */
 26 #define MXC_W1_RESET_TIMEOUT 500
 27 
 28 /*
 29  * MXC W1 Register offsets
 30  */
 31 #define MXC_W1_CONTROL          0x00
 32 # define MXC_W1_CONTROL_RDST    BIT(3)
 33 # define MXC_W1_CONTROL_WR(x)   BIT(5 - (x))
 34 # define MXC_W1_CONTROL_PST     BIT(6)
 35 # define MXC_W1_CONTROL_RPP     BIT(7)
 36 #define MXC_W1_TIME_DIVIDER     0x02
 37 #define MXC_W1_RESET            0x04
 38 
 39 struct mxc_w1_device {
 40         void __iomem *regs;
 41         struct clk *clk;
 42         struct w1_bus_master bus_master;
 43 };
 44 
 45 /*
 46  * this is the low level routine to
 47  * reset the device on the One Wire interface
 48  * on the hardware
 49  */
 50 static u8 mxc_w1_ds2_reset_bus(void *data)
 51 {
 52         u8 reg_val;
 53         unsigned int timeout_cnt = 0;
 54         struct mxc_w1_device *dev = data;
 55 
 56         writeb(MXC_W1_CONTROL_RPP, (dev->regs + MXC_W1_CONTROL));
 57 
 58         while (1) {
 59                 reg_val = readb(dev->regs + MXC_W1_CONTROL);
 60 
 61                 if (!(reg_val & MXC_W1_CONTROL_RPP) ||
 62                     timeout_cnt > MXC_W1_RESET_TIMEOUT)
 63                         break;
 64                 else
 65                         timeout_cnt++;
 66 
 67                 udelay(100);
 68         }
 69         return !(reg_val & MXC_W1_CONTROL_PST);
 70 }
 71 
 72 /*
 73  * this is the low level routine to read/write a bit on the One Wire
 74  * interface on the hardware. It does write 0 if parameter bit is set
 75  * to 0, otherwise a write 1/read.
 76  */
 77 static u8 mxc_w1_ds2_touch_bit(void *data, u8 bit)
 78 {
 79         struct mxc_w1_device *mdev = data;
 80         void __iomem *ctrl_addr = mdev->regs + MXC_W1_CONTROL;
 81         unsigned int timeout_cnt = 400; /* Takes max. 120us according to
 82                                          * datasheet.
 83                                          */
 84 
 85         writeb(MXC_W1_CONTROL_WR(bit), ctrl_addr);
 86 
 87         while (timeout_cnt--) {
 88                 if (!(readb(ctrl_addr) & MXC_W1_CONTROL_WR(bit)))
 89                         break;
 90 
 91                 udelay(1);
 92         }
 93 
 94         return !!(readb(ctrl_addr) & MXC_W1_CONTROL_RDST);
 95 }
 96 
 97 static int mxc_w1_probe(struct platform_device *pdev)
 98 {
 99         struct mxc_w1_device *mdev;
100         unsigned long clkrate;
101         struct resource *res;
102         unsigned int clkdiv;
103         int err;
104 
105         mdev = devm_kzalloc(&pdev->dev, sizeof(struct mxc_w1_device),
106                             GFP_KERNEL);
107         if (!mdev)
108                 return -ENOMEM;
109 
110         mdev->clk = devm_clk_get(&pdev->dev, NULL);
111         if (IS_ERR(mdev->clk))
112                 return PTR_ERR(mdev->clk);
113 
114         clkrate = clk_get_rate(mdev->clk);
115         if (clkrate < 10000000)
116                 dev_warn(&pdev->dev,
117                          "Low clock frequency causes improper function\n");
118 
119         clkdiv = DIV_ROUND_CLOSEST(clkrate, 1000000);
120         clkrate /= clkdiv;
121         if ((clkrate < 980000) || (clkrate > 1020000))
122                 dev_warn(&pdev->dev,
123                          "Incorrect time base frequency %lu Hz\n", clkrate);
124 
125         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
126         mdev->regs = devm_ioremap_resource(&pdev->dev, res);
127         if (IS_ERR(mdev->regs))
128                 return PTR_ERR(mdev->regs);
129 
130         err = clk_prepare_enable(mdev->clk);
131         if (err)
132                 return err;
133 
134         writeb(clkdiv - 1, mdev->regs + MXC_W1_TIME_DIVIDER);
135 
136         mdev->bus_master.data = mdev;
137         mdev->bus_master.reset_bus = mxc_w1_ds2_reset_bus;
138         mdev->bus_master.touch_bit = mxc_w1_ds2_touch_bit;
139 
140         platform_set_drvdata(pdev, mdev);
141 
142         err = w1_add_master_device(&mdev->bus_master);
143         if (err)
144                 clk_disable_unprepare(mdev->clk);
145 
146         return err;
147 }
148 
149 /*
150  * disassociate the w1 device from the driver
151  */
152 static int mxc_w1_remove(struct platform_device *pdev)
153 {
154         struct mxc_w1_device *mdev = platform_get_drvdata(pdev);
155 
156         w1_remove_master_device(&mdev->bus_master);
157 
158         clk_disable_unprepare(mdev->clk);
159 
160         return 0;
161 }
162 
163 static struct of_device_id mxc_w1_dt_ids[] = {
164         { .compatible = "fsl,imx21-owire" },
165         { /* sentinel */ }
166 };
167 MODULE_DEVICE_TABLE(of, mxc_w1_dt_ids);
168 
169 static struct platform_driver mxc_w1_driver = {
170         .driver = {
171                 .name = "mxc_w1",
172                 .owner = THIS_MODULE,
173                 .of_match_table = mxc_w1_dt_ids,
174         },
175         .probe = mxc_w1_probe,
176         .remove = mxc_w1_remove,
177 };
178 module_platform_driver(mxc_w1_driver);
179 
180 MODULE_LICENSE("GPL");
181 MODULE_AUTHOR("Freescale Semiconductors Inc");
182 MODULE_DESCRIPTION("Driver for One-Wire on MXC");
183 

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