diff options
Diffstat (limited to 'drivers/w1/masters/mxc_w1.c')
| -rw-r--r-- | drivers/w1/masters/mxc_w1.c | 183 |
1 files changed, 183 insertions, 0 deletions
diff --git a/drivers/w1/masters/mxc_w1.c b/drivers/w1/masters/mxc_w1.c new file mode 100644 index 0000000000..090cbbf9e1 --- /dev/null +++ b/drivers/w1/masters/mxc_w1.c @@ -0,0 +1,183 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright 2005-2008 Freescale Semiconductor, Inc. All Rights Reserved. + * Copyright 2008 Luotao Fu, kernel@pengutronix.de + */ + +#include <linux/clk.h> +#include <linux/delay.h> +#include <linux/io.h> +#include <linux/ktime.h> +#include <linux/module.h> +#include <linux/mod_devicetable.h> +#include <linux/platform_device.h> + +#include <linux/w1.h> + +/* + * 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 +# define MXC_W1_RESET_RST BIT(0) + +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) +{ + struct mxc_w1_device *dev = data; + ktime_t timeout; + + writeb(MXC_W1_CONTROL_RPP, dev->regs + MXC_W1_CONTROL); + + /* Wait for reset sequence 511+512us, use 1500us for sure */ + timeout = ktime_add_us(ktime_get(), 1500); + + udelay(511 + 512); + + do { + u8 ctrl = readb(dev->regs + MXC_W1_CONTROL); + + /* PST bit is valid after the RPP bit is self-cleared */ + if (!(ctrl & MXC_W1_CONTROL_RPP)) + return !(ctrl & MXC_W1_CONTROL_PST); + } while (ktime_before(ktime_get(), timeout)); + + return 1; +} + +/* + * 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 *dev = data; + ktime_t timeout; + + writeb(MXC_W1_CONTROL_WR(bit), dev->regs + MXC_W1_CONTROL); + + /* Wait for read/write bit (60us, Max 120us), use 200us for sure */ + timeout = ktime_add_us(ktime_get(), 200); + + udelay(60); + + do { + u8 ctrl = readb(dev->regs + MXC_W1_CONTROL); + + /* RDST bit is valid after the WR1/RD bit is self-cleared */ + if (!(ctrl & MXC_W1_CONTROL_WR(bit))) + return !!(ctrl & MXC_W1_CONTROL_RDST); + } while (ktime_before(ktime_get(), timeout)); + + return 0; +} + +static int mxc_w1_probe(struct platform_device *pdev) +{ + struct mxc_w1_device *mdev; + unsigned long clkrate; + 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); + + err = clk_prepare_enable(mdev->clk); + if (err) + return err; + + 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); + + mdev->regs = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(mdev->regs)) { + err = PTR_ERR(mdev->regs); + goto out_disable_clk; + } + + /* Software reset 1-Wire module */ + writeb(MXC_W1_RESET_RST, mdev->regs + MXC_W1_RESET); + writeb(0, mdev->regs + MXC_W1_RESET); + + 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) + goto out_disable_clk; + + return 0; + +out_disable_clk: + 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 const 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", + .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"); |