diff options
Diffstat (limited to 'drivers/w1/masters/mxc_w1.c')
| -rw-r--r-- | drivers/w1/masters/mxc_w1.c | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/drivers/w1/masters/mxc_w1.c b/drivers/w1/masters/mxc_w1.c new file mode 100644 index 00000000000..a5df5e89d45 --- /dev/null +++ b/drivers/w1/masters/mxc_w1.c @@ -0,0 +1,182 @@ +/* + * Copyright 2005-2008 Freescale Semiconductor, Inc. All Rights Reserved. + * Copyright 2008 Luotao Fu, kernel@pengutronix.de + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include <linux/clk.h> +#include <linux/delay.h> +#include <linux/io.h> +#include <linux/module.h> +#include <linux/platform_device.h> + +#include "../w1.h" +#include "../w1_int.h" + +/* According to the mx27 Datasheet the reset procedure should take up to about + * 1350us. We set the timeout to 500*100us = 50ms for sure */ +#define MXC_W1_RESET_TIMEOUT 500 + +/* + * MXC W1 Register offsets + */ +#define MXC_W1_CONTROL 0x00 +# define MXC_W1_CONTROL_RDST BIT(3) +# define MXC_W1_CONTROL_WR(x) BIT(5 - (x)) +# define MXC_W1_CONTROL_PST BIT(6) +# define MXC_W1_CONTROL_RPP BIT(7) +#define MXC_W1_TIME_DIVIDER 0x02 +#define MXC_W1_RESET 0x04 + +struct mxc_w1_device { + void __iomem *regs; + struct clk *clk; + struct w1_bus_master bus_master; +}; + +/* + * this is the low level routine to + * reset the device on the One Wire interface + * on the hardware + */ +static u8 mxc_w1_ds2_reset_bus(void *data) +{ + u8 reg_val; + unsigned int timeout_cnt = 0; + struct mxc_w1_device *dev = data; + + writeb(MXC_W1_CONTROL_RPP, (dev->regs + MXC_W1_CONTROL)); + + while (1) { + reg_val = readb(dev->regs + MXC_W1_CONTROL); + + if (!(reg_val & MXC_W1_CONTROL_RPP) || + timeout_cnt > MXC_W1_RESET_TIMEOUT) + break; + else + timeout_cnt++; + + udelay(100); + } + return !(reg_val & MXC_W1_CONTROL_PST); +} + +/* + * this is the low level routine to read/write a bit on the One Wire + * interface on the hardware. It does write 0 if parameter bit is set + * to 0, otherwise a write 1/read. + */ +static u8 mxc_w1_ds2_touch_bit(void *data, u8 bit) +{ + struct mxc_w1_device *mdev = data; + void __iomem *ctrl_addr = mdev->regs + MXC_W1_CONTROL; + unsigned int timeout_cnt = 400; /* Takes max. 120us according to + * datasheet. + */ + + writeb(MXC_W1_CONTROL_WR(bit), ctrl_addr); + + while (timeout_cnt--) { + if (!(readb(ctrl_addr) & MXC_W1_CONTROL_WR(bit))) + break; + + udelay(1); + } + + return !!(readb(ctrl_addr) & MXC_W1_CONTROL_RDST); +} + +static int mxc_w1_probe(struct platform_device *pdev) +{ + struct mxc_w1_device *mdev; + unsigned long clkrate; + struct resource *res; + unsigned int clkdiv; + int err; + + mdev = devm_kzalloc(&pdev->dev, sizeof(struct mxc_w1_device), + GFP_KERNEL); + if (!mdev) + return -ENOMEM; + + mdev->clk = devm_clk_get(&pdev->dev, NULL); + if (IS_ERR(mdev->clk)) + return PTR_ERR(mdev->clk); + + clkrate = clk_get_rate(mdev->clk); + if (clkrate < 10000000) + dev_warn(&pdev->dev, + "Low clock frequency causes improper function\n"); + + clkdiv = DIV_ROUND_CLOSEST(clkrate, 1000000); + clkrate /= clkdiv; + if ((clkrate < 980000) || (clkrate > 1020000)) + dev_warn(&pdev->dev, + "Incorrect time base frequency %lu Hz\n", clkrate); + + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + mdev->regs = devm_ioremap_resource(&pdev->dev, res); + if (IS_ERR(mdev->regs)) + return PTR_ERR(mdev->regs); + + err = clk_prepare_enable(mdev->clk); + if (err) + return err; + + writeb(clkdiv - 1, mdev->regs + MXC_W1_TIME_DIVIDER); + + mdev->bus_master.data = mdev; + mdev->bus_master.reset_bus = mxc_w1_ds2_reset_bus; + mdev->bus_master.touch_bit = mxc_w1_ds2_touch_bit; + + platform_set_drvdata(pdev, mdev); + + err = w1_add_master_device(&mdev->bus_master); + if (err) + clk_disable_unprepare(mdev->clk); + + return err; +} + +/* + * disassociate the w1 device from the driver + */ +static int mxc_w1_remove(struct platform_device *pdev) +{ + struct mxc_w1_device *mdev = platform_get_drvdata(pdev); + + w1_remove_master_device(&mdev->bus_master); + + clk_disable_unprepare(mdev->clk); + + return 0; +} + +static struct of_device_id mxc_w1_dt_ids[] = { + { .compatible = "fsl,imx21-owire" }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, mxc_w1_dt_ids); + +static struct platform_driver mxc_w1_driver = { + .driver = { + .name = "mxc_w1", + .owner = THIS_MODULE, + .of_match_table = mxc_w1_dt_ids, + }, + .probe = mxc_w1_probe, + .remove = mxc_w1_remove, +}; +module_platform_driver(mxc_w1_driver); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Freescale Semiconductors Inc"); +MODULE_DESCRIPTION("Driver for One-Wire on MXC"); |