From: Maxime Ripard maxime.ripard@free-electrons.com
Add a bus driver for bitbanging a 1-Wire bus over a GPIO.
Signed-off-by: Maxime Ripard maxime.ripard@bootlin.com [eugen.hristev@microchip.com: fixed some issues] Signed-off-by: Eugen Hristev eugen.hristev@microchip.com --- drivers/w1/Kconfig | 7 ++ drivers/w1/Makefile | 2 + drivers/w1/w1-gpio.c | 176 +++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 185 insertions(+) create mode 100644 drivers/w1/w1-gpio.c
diff --git a/drivers/w1/Kconfig b/drivers/w1/Kconfig index 64b27c6..d6e0457 100644 --- a/drivers/w1/Kconfig +++ b/drivers/w1/Kconfig @@ -13,6 +13,13 @@ config W1
if W1
+config W1_GPIO + bool "Enable 1-wire GPIO bitbanging" + default no + depends on DM_GPIO + help + Emulate a 1-wire bus using a GPIO. + endif
endmenu diff --git a/drivers/w1/Makefile b/drivers/w1/Makefile index f81693b..7fd8697 100644 --- a/drivers/w1/Makefile +++ b/drivers/w1/Makefile @@ -1 +1,3 @@ obj-$(CONFIG_W1) += w1-uclass.o + +obj-$(CONFIG_W1_GPIO) += w1-gpio.o diff --git a/drivers/w1/w1-gpio.c b/drivers/w1/w1-gpio.c new file mode 100644 index 0000000..5e5d6b3 --- /dev/null +++ b/drivers/w1/w1-gpio.c @@ -0,0 +1,176 @@ +/* SPDX-License-Identifier: GPL-2.0+ + * + * Copyright (c) 2015 Free Electrons + * Copyright (c) 2015 NextThing Co + * + * Maxime Ripard maxime.ripard@free-electrons.com + * + */ + +#include <common.h> +#include <dm.h> +#include <w1.h> + +#include <asm/gpio.h> + +#define W1_TIMING_A 6 +#define W1_TIMING_B 64 +#define W1_TIMING_C 60 +#define W1_TIMING_D 10 +#define W1_TIMING_E 9 +#define W1_TIMING_F 55 +#define W1_TIMING_G 0 +#define W1_TIMING_H 480 +#define W1_TIMING_I 70 +#define W1_TIMING_J 410 + +struct w1_gpio_pdata { + struct gpio_desc gpio; + u64 search_id; +}; + +static bool w1_gpio_read_bit(struct udevice *dev) +{ + struct w1_gpio_pdata *pdata = dev_get_platdata(dev); + int val; + + dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_OUT); + udelay(W1_TIMING_A); + + dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_IN); + udelay(W1_TIMING_E); + + val = dm_gpio_get_value(&pdata->gpio); + if (val < 0) + debug("error in retrieving GPIO value"); + udelay(W1_TIMING_F); + + return val; +} + +static u8 w1_gpio_read_byte(struct udevice *dev) +{ + int i; + u8 ret = 0; + + for (i = 0; i < 8; ++i) + ret |= (w1_gpio_read_bit(dev) ? 1 : 0) << i; + + return ret; +} + +static void w1_gpio_write_bit(struct udevice *dev, bool bit) +{ + struct w1_gpio_pdata *pdata = dev_get_platdata(dev); + + dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_OUT); + + bit ? udelay(W1_TIMING_A) : udelay(W1_TIMING_C); + + dm_gpio_set_value(&pdata->gpio, 1); + + bit ? udelay(W1_TIMING_B) : udelay(W1_TIMING_D); +} + +static void w1_gpio_write_byte(struct udevice *dev, u8 byte) +{ + int i; + + for (i = 0; i < 8; ++i) + w1_gpio_write_bit(dev, (byte >> i) & 0x1); +} + +static bool w1_gpio_reset(struct udevice *dev) +{ + struct w1_gpio_pdata *pdata = dev_get_platdata(dev); + int val; + + /* initiate the reset pulse. first we must pull the bus to low */ + dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_OUT | GPIOD_IS_OUT_ACTIVE); + udelay(W1_TIMING_G); + + dm_gpio_set_value(&pdata->gpio, 0); + /* wait for the specified time with the bus kept low */ + udelay(W1_TIMING_H); + + /* now we must read the presence pulse */ + dm_gpio_set_dir_flags(&pdata->gpio, GPIOD_IS_IN); + udelay(W1_TIMING_I); + + val = dm_gpio_get_value(&pdata->gpio); + if (val < 0) + debug("error in retrieving GPIO value"); + + /* if nobody pulled the bus down , it means nobody is on the bus */ + if (val != 0) + return 1; + /* we have the bus pulled down, let's wait for the specified presence time */ + udelay(W1_TIMING_J); + + /* read again, the other end should leave the bus free */ + val = dm_gpio_get_value(&pdata->gpio); + if (val < 0) + debug("error in retrieving GPIO value"); + + /* bus is not going up again, so we have an error */ + if (val != 1) + return 1; + + /* all good, presence detected */ + return 0; +} + +static u8 w1_gpio_triplet(struct udevice *dev, bool bdir) +{ + u8 id_bit = w1_gpio_read_bit(dev); + u8 comp_bit = w1_gpio_read_bit(dev); + u8 retval; + + if (id_bit && comp_bit) + return 0x03; /* error */ + + if (!id_bit && !comp_bit) { + /* Both bits are valid, take the direction given */ + retval = bdir ? 0x04 : 0; + } else { + /* Only one bit is valid, take that direction */ + bdir = id_bit; + retval = id_bit ? 0x05 : 0x02; + } + + w1_gpio_write_bit(dev, bdir); + return retval; +} + +static const struct w1_ops w1_gpio_ops = { + .read_byte = w1_gpio_read_byte, + .reset = w1_gpio_reset, + .triplet = w1_gpio_triplet, + .write_byte = w1_gpio_write_byte, +}; + +static int w1_gpio_ofdata_to_platdata(struct udevice *dev) +{ + struct w1_gpio_pdata *pdata = dev_get_platdata(dev); + int ret; + + ret = gpio_request_by_name(dev, "gpios", 0, &pdata->gpio, 0); + if (ret < 0) + printf("Error claiming GPIO %d\n", ret); + + return ret; +}; + +static const struct udevice_id w1_gpio_id[] = { + { "w1-gpio", 0 }, + { }, +}; + +U_BOOT_DRIVER(w1_gpio_drv) = { + .id = UCLASS_W1, + .name = "w1_gpio_drv", + .of_match = w1_gpio_id, + .ofdata_to_platdata = w1_gpio_ofdata_to_platdata, + .ops = &w1_gpio_ops, + .platdata_auto_alloc_size = sizeof(struct w1_gpio_pdata), +};