w1: Add 1-Wire gpio driver

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

@@ -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

drivers/w1/Makefile

@@ -1 +1,3 @@
 obj-$(CONFIG_W1) += w1-uclass.o
+
+obj-$(CONFIG_W1_GPIO) += w1-gpio.o

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),
+};