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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  * You should have received a copy of the GNU General Public License
 15  * along with this program; if not, write to the Free Software
 16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 17  *
 18  */
 19 
 20 #include <linux/module.h>
 21 #include <linux/interrupt.h>
 22 #include <linux/platform_device.h>
 23 #include <linux/clk.h>
 24 #include <linux/slab.h>
 25 #include <linux/delay.h>
 26 #include <linux/io.h>
 27 
 28 #include "../w1.h"
 29 #include "../w1_int.h"
 30 #include "../w1_log.h"
 31 
 32 /* According to the mx27 Datasheet the reset procedure should take up to about
 33  * 1350us. We set the timeout to 500*100us = 50ms for sure */
 34 #define MXC_W1_RESET_TIMEOUT 500
 35 
 36 /*
 37  * MXC W1 Register offsets
 38  */
 39 #define MXC_W1_CONTROL          0x00
 40 #define MXC_W1_TIME_DIVIDER     0x02
 41 #define MXC_W1_RESET            0x04
 42 #define MXC_W1_COMMAND          0x06
 43 #define MXC_W1_TXRX             0x08
 44 #define MXC_W1_INTERRUPT        0x0A
 45 #define MXC_W1_INTERRUPT_EN     0x0C
 46 
 47 struct mxc_w1_device {
 48         void __iomem *regs;
 49         struct clk *clk;
 50         struct w1_bus_master bus_master;
 51 };
 52 
 53 /*
 54  * this is the low level routine to
 55  * reset the device on the One Wire interface
 56  * on the hardware
 57  */
 58 static u8 mxc_w1_ds2_reset_bus(void *data)
 59 {
 60         u8 reg_val;
 61         unsigned int timeout_cnt = 0;
 62         struct mxc_w1_device *dev = data;
 63 
 64         __raw_writeb(0x80, (dev->regs + MXC_W1_CONTROL));
 65 
 66         while (1) {
 67                 reg_val = __raw_readb(dev->regs + MXC_W1_CONTROL);
 68 
 69                 if (((reg_val >> 7) & 0x1) == 0 ||
 70                     timeout_cnt > MXC_W1_RESET_TIMEOUT)
 71                         break;
 72                 else
 73                         timeout_cnt++;
 74 
 75                 udelay(100);
 76         }
 77         return (reg_val >> 7) & 0x1;
 78 }
 79 
 80 /*
 81  * this is the low level routine to read/write a bit on the One Wire
 82  * interface on the hardware. It does write 0 if parameter bit is set
 83  * to 0, otherwise a write 1/read.
 84  */
 85 static u8 mxc_w1_ds2_touch_bit(void *data, u8 bit)
 86 {
 87         struct mxc_w1_device *mdev = data;
 88         void __iomem *ctrl_addr = mdev->regs + MXC_W1_CONTROL;
 89         unsigned int timeout_cnt = 400; /* Takes max. 120us according to
 90                                          * datasheet.
 91                                          */
 92 
 93         __raw_writeb((1 << (5 - bit)), ctrl_addr);
 94 
 95         while (timeout_cnt--) {
 96                 if (!((__raw_readb(ctrl_addr) >> (5 - bit)) & 0x1))
 97                         break;
 98 
 99                 udelay(1);
100         }
101 
102         return ((__raw_readb(ctrl_addr)) >> 3) & 0x1;
103 }
104 
105 static int mxc_w1_probe(struct platform_device *pdev)
106 {
107         struct mxc_w1_device *mdev;
108         unsigned long clkrate;
109         struct resource *res;
110         unsigned int clkdiv;
111         int err;
112 
113         mdev = devm_kzalloc(&pdev->dev, sizeof(struct mxc_w1_device),
114                             GFP_KERNEL);
115         if (!mdev)
116                 return -ENOMEM;
117 
118         mdev->clk = devm_clk_get(&pdev->dev, NULL);
119         if (IS_ERR(mdev->clk))
120                 return PTR_ERR(mdev->clk);
121 
122         clkrate = clk_get_rate(mdev->clk);
123         if (clkrate < 10000000)
124                 dev_warn(&pdev->dev,
125                          "Low clock frequency causes improper function\n");
126 
127         clkdiv = DIV_ROUND_CLOSEST(clkrate, 1000000);
128         clkrate /= clkdiv;
129         if ((clkrate < 980000) || (clkrate > 1020000))
130                 dev_warn(&pdev->dev,
131                          "Incorrect time base frequency %lu Hz\n", clkrate);
132 
133         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
134         mdev->regs = devm_ioremap_resource(&pdev->dev, res);
135         if (IS_ERR(mdev->regs))
136                 return PTR_ERR(mdev->regs);
137 
138         err = clk_prepare_enable(mdev->clk);
139         if (err)
140                 return err;
141 
142         __raw_writeb(clkdiv - 1, mdev->regs + MXC_W1_TIME_DIVIDER);
143 
144         mdev->bus_master.data = mdev;
145         mdev->bus_master.reset_bus = mxc_w1_ds2_reset_bus;
146         mdev->bus_master.touch_bit = mxc_w1_ds2_touch_bit;
147 
148         platform_set_drvdata(pdev, mdev);
149 
150         err = w1_add_master_device(&mdev->bus_master);
151         if (err)
152                 clk_disable_unprepare(mdev->clk);
153 
154         return err;
155 }
156 
157 /*
158  * disassociate the w1 device from the driver
159  */
160 static int mxc_w1_remove(struct platform_device *pdev)
161 {
162         struct mxc_w1_device *mdev = platform_get_drvdata(pdev);
163 
164         w1_remove_master_device(&mdev->bus_master);
165 
166         clk_disable_unprepare(mdev->clk);
167 
168         return 0;
169 }
170 
171 static struct of_device_id mxc_w1_dt_ids[] = {
172         { .compatible = "fsl,imx21-owire" },
173         { /* sentinel */ }
174 };
175 MODULE_DEVICE_TABLE(of, mxc_w1_dt_ids);
176 
177 static struct platform_driver mxc_w1_driver = {
178         .driver = {
179                 .name = "mxc_w1",
180                 .of_match_table = mxc_w1_dt_ids,
181         },
182         .probe = mxc_w1_probe,
183         .remove = mxc_w1_remove,
184 };
185 module_platform_driver(mxc_w1_driver);
186 
187 MODULE_LICENSE("GPL");
188 MODULE_AUTHOR("Freescale Semiconductors Inc");
189 MODULE_DESCRIPTION("Driver for One-Wire on MXC");
190 

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